Dissertations / Theses: 'Acoustic identification'

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Silva, Bruno Miguel Santos Antunes. "Automated acoustic identification of bat species." Master's thesis, Universidade de Évora, 2013. http://hdl.handle.net/10174/9101.

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Automated acoustic identification of bat species Recent improvements in bat survey methods in Portugal, especially automatic recording stations, have led to an analysis problem due to the amount of data obtained. In this thesis we propose to develop an automated analysis and classification method for bat echolocation calls by developing a computer program based on statistical models and using a reference database of bat calls recorded in Portugal to quickly analyze and classify large amounts of recordings. We recorded 2968 calls from 748 bats of 20 (of the 25) bat species known in mainland Portugal and coded a program in R that automatically detects bat calls in a recording, isolates the calls from the background noise and measures 19 parameters from each call. A two stage hierarchical classification bat call scheme was implemented based on logistic regression models and ensembles of artificial neural networks. In the first stage calls were classified in six major groups with individual correct classification rates that varied between 93% and 100%. In the second stage calls were classified in species or groups of species with classification rates that varied between 50% and 100%; ### Identificação acústica automatizada de espécies de morcegos Desenvolvimentos recentes nas metodologias de monitorização de morcegos utilizadas em Portugal, especialmente estações de gravação automáticas, conduziram a um problema de análise devido à quantidade de dados obtida. Nesta tese propomos desenvolver um método automatizado de análise e classificação de pulsos de ecolocalização de morcegos através do desenvolvimento de um programa de computador baseado em modelos estatísticos e utilizando uma base de dados de pulsos de morcegos gravados em Portugal continental para rapidamente analisar e classificar grandes quantidades de gravações. Gravámos 2968 pulsos de 748 morcegos de 20 (das 25) espécies de morcegos conhecidas em Portugal continental e codificámos em R um programa para automaticamente detectar pulsos de morcego numa gravação, isolar os pulsos do ruído de fundo e medir 19 parâmetros de cada pulso. Foi implementado um esquema hierárquico de classificação de pulsos em duas etapas baseado em modelos de regressão logística e conjuntos de redes neuronais artificiais. Numa primeira etapa os pulsos foram classificados em seis grupos com taxas individuais de classificações correctas que variaram entre 93% e 100%. Numa segunda fase os pulsos foram classificados em espécies ou grupos de espécies com taxas de classificação correctas que variaram entre 50% e 100%.

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Cabell, Randolph H. "The automatic identification of aerospace acoustic sources." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/45932.

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This work describes the design of an intelligent recognition system used to distinguish noise signatures of five different acoustic sources. The system uses pattern recognition techniques to identify the information obtained from a single microphone. A training phase is used in which the system learns to distinguish the sources and automatically selects features for optimal performance. Results were obtained by training the system to distinguish jet planes, propeller planes, a helicopter, train, and wind turbine from one another, then presenting similar sources to the system and recording the number of errors. These results indicate the system can successfully identify the trained sources based on acoustic information. Classification errors highlight the impact of the training sources on the system's ability to recognize different sources.

Master of Science

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DeMarco, Andrea. "Acoustic approaches to gender and accent identification." Thesis, University of East Anglia, 2015. https://ueaeprints.uea.ac.uk/53443/.

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There has been considerable research on the problems of speaker and language recognition from samples of speech. A less researched problem is that of accent recognition. Although this is a similar problem to language identification, different accents of a language exhibit more fine-grained differences between classes than languages. This presents a tougher problem for traditional classification techniques. In this thesis, we propose and evaluate a number of techniques for gender and accent classification. These techniques are novel modifications and extensions to state of the art algorithms, and they result in enhanced performance on gender and accent recognition. The first part of the thesis focuses on the problem of gender identification, and presents a technique that gives improved performance in situations where training and test conditions are mismatched. The bulk of this thesis is concerned with the application of the i-Vector technique to accent identification, which is the most successful approach to acoustic classification to have emerged in recent years. We show that it is possible to achieve high accuracy accent identification without reliance on transcriptions and without utilising phoneme recognition algorithms. The thesis describes various stages in the development of i-Vector based accent classification that improve the standard approaches usually applied for speaker or language identification, which are insufficient. We demonstrate that very good accent identification performance is possible with acoustic methods by considering different i-Vector projections, frontend parameters, i-Vector configuration parameters, and an optimised fusion of the resulting i-Vector classifiers we can obtain from the same data. We claim to have achieved the best accent identification performance on the test corpus for acoustic methods, with up to 90% identification rate. This performance is even better than previously reported acoustic-phonotactic based systems on the same corpus, and is very close to performance obtained via transcription based accent identification. Finally, we demonstrate that the utilization of our techniques for speech recognition purposes leads to considerably lower word error rates.

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Fox, Elizabeth J. S. "Call-independent identification in birds." University of Western Australia. School of Animal Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0218.

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[Truncated abstract] The identification of individual animals based on acoustic parameters is a non-invasive method of identifying individuals with considerable advantages over physical marking procedures. One requirement for an effective and practical method of acoustic individual identification is that it is call-independent, i.e. determining identity does not require a comparison of the same call or song type. This means that an individuals identity over time can be determined regardless of any changes to its vocal repertoire, and different individuals can be compared regardless of whether they share calls. Although several methods of acoustic identification currently exist, for example discriminant function analysis or spectrographic cross-correlation, none are call-independent. Call-independent identification has been developed for human speaker recognition, and this thesis aimed to: 1) determine if call-independent identification was possible in birds, using similar methods to those used for human speaker recognition, 2) examine the impact of noise in a recording on the identification accuracy and determine methods of removing the noise and increasing accuracy, 3) provide a comparison of features and classifiers to determine the best method of call-independent identification in birds, and 4) determine the practical limitations of call-independent identification in birds, with respect to increasing population size, changing vocal characteristics over time, using different call categories, and using the method in an open population. ... For classification, Gaussian mixture models and probabilistic neural networks resulted in higher accuracy, and were simpler to use, than multilayer perceptrons. Using the best methods of feature extraction and classification resulted in 86-95.5% identification accuracy for two passerine species, with all individuals correctly identified. A study of the limitations of the technique, in terms of population size, the category of call used, accuracy over time, and the effects of having an open population, found that acoustic identification using perceptual linear prediction and probabilistic neural networks can be used to successfully identify individuals in a population of at least 40 individuals, can be used successfully on call categories other than song, and can be used in open populations in which a new recording may belong to a previously unknown individual. However, identity was only able to be determined with accuracy for less than three months, limiting the current technique to short-term field studies. This thesis demonstrates the application of speaker recognition technology to enable call-independent identification in birds. Call-independence is a pre-requisite for the successful application of acoustic individual identification in many species, especially passerines, but has so far received little attention in the scientific literature. This thesis demonstrates that call-independent identification is possible in birds, as well as testing and finding methods to overcome the practical limitations of the methods, enabling their future use in biological studies, particularly for the conservation of threatened species.

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Schuler, Leo Pius. "Wireless identification and sensing using surface acoustic wave devices." Thesis, University of Canterbury. Electrical Engineering, 2003. http://hdl.handle.net/10092/1081.

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Wireless Surface Acoustic Wave (SAW) devices were fabricated and tested using planar Lithium Niobate (LiNbO₃) as substrate. The working frequencies were in the 180 MHz and 360 MHz range. Using a network analyser, the devices were interrogated with a wireless range of more than 2 metres. Trials with Electron Beam Lithography (EBL) to fabricate SAW devices working in the 2450 MHz with a calculated feature size of 350 nm are discussed. Charging problems became evident as LiNbO₃ is a strong piezoelectric and pyroelectric material. Various attempts were undertaken to neutralise the charging problems. Further investigation revealed that sputtered Zinc Oxide (ZnO) is a suitable material for attaching SAW devices on irregularly shaped material. DC sputtering was used and several parameters have been optimised to achieve the desired piezoelectric effect. ZnO was sputtered using a magnetron sputtering system with a 75 mm Zn target and a DC sputter power of 250 Watts. Several trials were performed and an optimised material has been prepared under the following conditions: 9 sccm of Oxygen and 6 sccm of Argon were introduced during the process which resulted in a process pressure of 1.2x10⁻² mbar. The coatings have been characterised using Rutherford Backscattering, X-ray diffraction, SEM imaging, and Atomic force microscopy. SAW devices were fabricated and tested on 600 nm thick sputtered ZnO on a Si substrate with a working frequency of 430 MHz. The phase velocity has been calculated as 4300m/s. Non-planar samples have been coated with 500 nm of sputtered ZnO and SAW structures have been fabricated on using EBL. The design frequency is 2450 MHz, with a calculated feature size of 1 µm. The surface roughness however prevented a successful lift-off. AFM imaging confirmed a surface roughness in the order of 20 nm. Ways to improve manufacturability on these samples have been identified.

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Schuler, Leo P. "Wireless identification and sensing using surface acoustic wave devices." Thesis, University of Canterbury. Engineering, 2003. http://hdl.handle.net/10092/8565.

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Wireless Surface Acoustic Wave (SAW) devices were fabricated and tested using planar Lithium Niobate (LiNbO₃) as substrate. The working frequencies were in the 180 MHz and 360 MHz range. Using a network analyser, the devices were interrogated with a wireless range of more than 2 metres. Trials with Electron Beam Lithography (EBL) to fabricate SAW devices working in the 2450 MHz with a calculated feature size of 350 nm are discussed. Charging problems became evident as LiNbO₃ is a strong piezoelectric and pyroelectric material. Various attempts were undertaken to neutralise the charging problems. Further investigation revealed that sputtered Zinc Oxide (ZnO) is a suitable material for attaching SAW devices on irregularly shaped material. DC sputtering was used and several parameters have been optimised to achieve the desired piezoelectric effect. ZnO was sputtered using a magnetron sputtering system with a 75 mm Zn target and a DC sputter power of 250 Watts. Several trials were performed and an optimised material has been prepared under the following conditions: 9 sccm of Oxygen and 6 seem of Argon were introduced during the process which resulted in a process pressure of 1.2x10⁻² mbar. The coatings have been characterised using Rutherford Backscattering, X-ray diffraction, SEM imaging, and Atomic force microscopy. SAW devices were fabricated and tested on 600 nm thick sputtered ZnO on a Si substrate with a working frequency of 430 MHz. The phase velocity has been calculated as 4300m/s. Non-planar samples have been coated with 500 nm of sputtered ZnO and SAW structures have been fabricated on using BBL. The design frequency is 2450 MHz, with a calculated feature size of 1 μm. The surface roughness however prevented a successful lift-off. AFM imaging confirmed a surface roughness in the order of 20 nm. Ways to improve manufacturability on these samples have been identified.

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Hedayetullah, Amin Mohammad. "Optimization of identification of particle impacts using acoustic emission." Thesis, Robert Gordon University, 2018. http://hdl.handle.net/10059/3116.

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Air borne or liquid-laden solid particle transport is a common phenomenon in various industrial applications. Solid particles, transported at severe operating conditions such as high flow velocity, can cause concerns for structural integrity through wear originated from particle impacts with structure. To apply Acoustic Emission (AE) in particle impact monitoring, previous researchers focused primarily on dry particle impacts on dry target plate and/or wet particle impacts on wet or dry target plate. For dry particle impacts on dry target plate, AE events energy, calculated from the recorded free falling or air borne particle impact AE signals, were correlated with particle size, concentration, height, target material and thickness. For a given system, once calibrated for a specific particle type and operating condition, this technique might be sufficient to serve the purpose. However, if more than one particle type present in the system, particularly with similar size, density and impact velocity, calculated AE event energy is not unique for a specific particle type. For wet particle impacts on dry or wet target plate (either submerged or in a flow loop), AE event energy was related to the particle size, concentration, target material, impact velocity and angle between the nozzle and the target plate. In these studies, the experimental arrangements and the operating conditions considered either did not allow any bubble formation in the system or even if there is any at least an order of magnitude lower in amplitude than the sand particle impact and so easily identifiable. In reality, bubble formation can be comparable with particle impacts in terms of AE amplitude in process industries, for example, sand production during oil and gas transportation from reservoir. Current practice is to calibrate an installed AE monitoring system against a range of sand free flow conditions. In real time monitoring, for a specific calibrated flow, the flow generated AE amplitude/energy is deducted from the recorded AE amplitude/energy and the difference is attributed to the sand particle impacts. However, if the flow condition changes, which often does in the process industry, the calibration is not valid anymore and AE events from bubble can be misinterpreted as sand particle impacts and vice versa. In this research, sand particles and glass beads with similar size, density and impact velocity have been studied dropping from 200 mm on a small cylindrical stepped mild steel coupon as a target plate. For signal recording purposes, two identical broadband AE sensors are installed, one at the centre and one 30 mm off centred, on the opposite of the impacting surface. Signal analysis have been carried out by evaluating 7 standard AE parameters (amplitude, energy, rise time, duration, power spectral density(PSD), peak frequency at PSD and spectral centroid) in the time and frequency domain and time-frequency domain analysis have been performed applying Gabor Wavelet Transform. The signal interpretation becomes difficult due to reflections, dispersions and mode conversions caused by close proximity of the boundaries. So, a new signal analysis parameter - frequency band energy ratio - has been proposed. This technique is able to distinguish between population of two very similar groups (in terms of size and mass and energy) of sand particles and glass beads, impacting on mild steel based on the coefficient of variation (Cv) of the frequency band AE energy ratios. To facilitate individual particle impact identification, further analysis has been performed using Support Vector Machine (SVM) based classification algorithm using 7 standard AE parameters, evaluated in both the time and frequency domain. Available data set has been segmented into two parts of training set (80%) and test set (20%). The developed model has been applied on the test data for model performance evaluation purpose. The overall success rate of individually identifying each category (PLB, Glass bead and Sand particle impacts) at S1 has been found as 86% and at S2 as 92%. To study wet particle impacts on wet target surface, in presence of bubbles, the target plate has been sealed to a cylindrical perspex tube. Single and multiple sand particles have been introduced in the system using a constant speed blower to impact the target surface under water loading. Two sensor locations, used in the previous sets of experiments, have been monitored. From frequency domain analysis it has been observed that characteristic frequency for particle impacts are centred at 300-350 kHz and for bubble formations are centred at 135 – 150 kHz. Based upon this, two frequency bands 100 – 200 kHz (E1) and 300 – 400 kHz (E3) and the frequency band energy ratio (E3E1,) have been identified as optimal for identification particle impacts for the given system. E3E1, > 1 has been associated with particle impacts and E3E1, < 1 has been associated with bubble formations. Applying these frequency band energy ratios and setting an amplitude threshold, an automatic event identification technique has been developed for identification of sand particle impacts in presence of bubbles. The method developed can be used to optimize the identification of sand particle impacts. The optimal setting of an amplitude threshold is sensitive to number of particles and noise levels. A high threshold of say 10% will clearly identify sand particle impacts but for multiparticle tests is likely to not detect about 20% of lower (impact) energy particles. A threshold lower than 3% is likely to result in detection of AE events with poor frequency content and wrong classification of the weakest events. Optimal setting of the parameters used in the framework such as thresholds, frequency bands and ratios of AE energy is likely to make identification of sand particle impacts in the laboratory environment within 10% possible. For this technique, once the optimal frequency bands and ratios have been identified, then an added advantage is that calibration of the signal levels is not required.

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Schofield, James. "Real-time acoustic identification of invasive wood-boring beetles." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1978/.

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Wood-boring beetles are a cause of significant economic and environmental cost across the world. A number of species which are not currently found in the United Kingdom are constantly at risk of being accidentally imported due to the volume of global trade in trees and timber. The species which are of particular concern are the Asian Longhorn (Anoplophora glabripennis), Citrus Longhorn (A. chinensis) and Emerald Ash Borer (Agrilus planipennis). The Food and Environment Research Agency's plant health inspectors currently manually inspect high risk material at the point of import. The development of methods which will enable them to increase the probability of detection of infestation in imported material are therefore highly sought after. This thesis describes research into improving acoustic larvae detection and species identification methods, and the development of a real-time system incorporating them. The detection algorithm is based upon fractal dimension analysis and has been shown to outperform previously used short-time energy based detection. This is the first time such a detection method has been applied to the analysis of insect sourced sounds. The species identification method combines a time domain feature extraction technique based upon the relational tree representation of discrete waveforms and classification using artificial neural networks. Classification between two species, A. glabripennis and H. bajulus, can be performed with 92% accuracy using Multilayer Perceptron and 96.5% accuracy using Linear Vector Quantisation networks. Classification between three species can be performed with 88.8% accuracy using LVQ. A real-time hand-held PC based system incorporating these methods has been developed and supplied to FERA for further testing. This system uses a combination of dual piezo-electric based USB connected sensors and custom written software which can be used to analyse live recordings of larvae in real-time or use previously recorded data.

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Moat, Trevor P. B. M. "Orthogonal adaptive digital filters with applications to acoustic system identification." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0025/MQ27022.pdf.

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Gaubitch, Nikolay Dian. "Blind identification of acoustic systems and enhancement of reverberant speech." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/12025.

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Radcliffe, Stewart Alexander. "Acoustical identification of the characteristics of ocean fronts." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245396.

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Kenny, Thomas Donald. "Identification of High-Velocity Pseudo-surface Acoustic Wave Substrate Orientations and Modeling of Surface Acoustic Wave Structures." Fogler Library, University of Maine, 2011. http://www.library.umaine.edu/theses/pdf/KennyT2011.pdf.

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Yang, Xi. "Discriminative acoustic and sequence models for GMM based automatic language identification /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?ECED%202007%20YANG.

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Hu, Mathieu. "Cross-relation based blind identification of acoustic SIMO systems and applications." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/52430.

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Speech signals captured by microphones placed at a distance from the speaker are cor- rupted by reverberation, i.e. sound waves reflected off hard surfaces such as walls and objects. The spectral distortion caused by reverberation drastically decreases the perfor- mance of automatic speech recognition systems and may degrade the intelligibility and the quality of speech for human listeners. The increased use of devices controlled by distant speech therefore induces the need for dereverberation. A possible approach to dereverberation is that of system equalization, which consists of the blind estimation of the room impulse responses from noisy reverberant signals followed by an inversion of these impulse responses. This thesis investigates the first part of this two-stage approach. The cross-relation method is adopted and exploited in two different ways. The first way follows the adaptive filter framework, which was first introduced in the context of blind identification of room impulses responses in the Multi-Channel Least Mean Square. By considering a block update of this stochastic gradient algorithm, a noise robust algorithm is developed. The convergence rate of the resulting algorithm is then increased by using a locally optimal adaptive step-size. The cross-relation, expressed in the frequency domain, is then shown to contain the transfer function relating any of the microphone to a reference microphone. This relative transfer function can be used to reduce the number of variables to be estimated. However, the performance of the previous methods severely degrades when realisti- cally long room impulse responses are considered. An alternative interpretation of the cross-relation, from an annihilation filter perspective, is therefore explored. The resulting algorithm is shown to be able to estimate room impulse responses of thousands of taps. From a more practical perspective, the use of room impulses estimated at a poor accuracy is investigated for the problem of speaker diarization. The spatial information captured in the direct-to-reverberant ratio is shown to be robust to high levels of errors in the estimated room impulse responses. Blindly estimated direct-to-reverberant ratios combined with speech features in a single-channel diarization system are shown to provide additional information, which improves the performance of the diarization system.

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Facciotto, Nicolò. "Source differentiation and identification of acoustic emission signals by time-frequency analysis." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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In the context of Structural Health Monitoring, the Acoustic Emission Technique may be efficiently used to detect damage on aerospace structures. This study focuses on the development of a source identification algorithm to distinguish different acoustic emission events in aluminium sheets, which have been collected during experimental tests. The future goal will be the design of a Holistic Structural Health Monitoring System which will make the complete aircraft an intelligent structure able to diagnose its own structural damage based on the condition of the structure while maintaining safety.

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Boukis, Christos. "Adaptive digital signal processing structures and identification algorithms for acoustic feedback control." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407894.

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Garudadri, Harinath. "Identification of invariant acoustic cues in stop consonants using the Wigner distribution." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/28786.

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It is a common belief that there are invariant acoustic patterns in speech signals, which can be related to their phonetic description. These patterns are expected to remain invariant, independent of the language, speaker, phonetic context, etc. Although many investigations based on short-time spectral analysis have established the feasibility of extracting invariant cues in certain contexts, they could not provide a set of invariant cues in any given phonetic context. In this thesis, the Wigner distribution (WD) was used to analyze speech signals for the first time, to investigate acoustic invariance. The WD, like the spectrogram, provides a time-frequency description of the signal. Unlike the spectrogram, it provides correct marginals in the time and frequency domains, but it is not a positive distribution. It is demonstrated here that the partially smoothed WD, in which both the properties of positivity and correct marginals are sacrificed to some extent, provides a better time-frequency resolution than short-time spectral analyses methods. An implementation and an interpretation of the partially smoothed WD are presented. The choice of smoothing parameters and the nature of cross-term suppression in a partially smoothed WD are discussed in detail. It is shown that the cross-terms in a partially smoothed WD do not mask the underlying nature of a signal in the time-frequency plane. A partially smoothed WD was used to investigate acoustic invariance in voiceless, unaspirated stop consonants spoken by native speakers of English, Telugu and French. Contrary to reports in the literature, it was shown that the features "diffuse-rising" and "compact" spectral shapes were not unique to alveolar and velar places of articulation, respectively, but depended on the vowel context. The resulting ambiguities when specifying the place of articulation were resolved using Formant Onset Duration (time taken for the steady state formants to occur in the vocal tract after the consonantal release) and F₂ of the following vowel. The place of articulation was specified correctly for 86% of the tokens. Unlike in other investigations, the errors in specifying the place of articulation were uniformly distributed over all vowel contexts.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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Lauritzen, Michael Kenneth. "Acoustic Mediation of Vocalized Emotion Identification: Do Decoders Identify Emotions Idiographically or Nomothetically?" Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3352.pdf.

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Rogers, Daniel James. "Intraspecific variation in the acoustic signals of birds and one species of frog : implications for the acoustic identification of individuals." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phr7251.pdf.

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Bibliography: leaves 203-218. This thesis investigated patterns of intraspecific variation in the acoustic signals of a range of vocal animal species with the ultimate objective of demonstrating vocal individuality in these species, focussing on two methods of quantitative song analysis, discriminant function analysis and cross-correlation analysis. Two species were studied: Bibron's toadlet (Pseudophryne bibronii) and Rufous bristlebird (Dasyornis broadbenti).

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Irons-Brown, Shunda R. "Identification of post-synaptic receptors mediating eighth nerve function." free online free to MU campus, others may purchase, 2002. http://wwwlib.umi.com/cr/mo/preview?3074410.

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Paxton, Scott. "System Identification and Optimization Methodologies for Active Structural Acoustic Control of Aircraft Cabin Noise." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/36876.

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There has been much recent research on the control of complex sound fields in enclosed vibrating structures via active control techniques. Active Structural Acoustic Control (ASAC) has shown much promise for reducing interior cabin noise in aircraft by applying control forces directly to the fuselage structure. Optimal positioning of force actuators for ASAC presents a challenging problem however, because a detailed knowledge of the structural-acoustic coupling in the fuselage is required.

This work is concerned with the development of a novel experimental technique for examining the forced harmonic vibrations of an aircraft fuselage and isolating the acoustically well-coupled motions that cause significant interior noise. The developed system identification technique is itself based upon an active control system, which is used to approximate the disturbance noise field in the cabin and apply an inverse excitation to the fuselage structure. The resulting shell vibrations are recorded and used to optimally locate piezoelectric (PZT) actuators on the fuselage for ASAC testing.

Experiments for this project made use of a Cessna Citation III aircraft fuselage test rig. Tests were performed at three harmonic disturbance frequencies, including an acoustic resonance, an off-resonance, and a structural resonance case. In all cases, the new system identification technique successfully isolated a simplified, low-magnitude vibration pattern from the total structural response caused by a force disturbance applied at the fuselage's rear engine mount. These measured well-coupled vibration components were used for positioning candidate piezoelectric actuators on the fuselage shell. A genetic algorithm search provided an optimal subset of actuators for use in an ASAC system. ASAC tests confirmed the importance of actuator location, as the optimal sets outperformed alternate groupings in all test cases. In addition, significant global control was achieved, with sound level reductions observed throughout the passenger cabin with virtually no control spillover.
Master of Science

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Sasidharan, Nair Unnikrishnan. "Jet noise source localization and identification." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1482412964456451.

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Frangakis, Stephanie. "Material parameter identification of acoustic polymeric foams via theoretical modeling and experimental measurements." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.41 Mb., 46 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430780.

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Chesnais, Corentin. "Holographie vibratoire : Identification et séparation de champs vibratoires." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI127/document.

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La reconstruction de champ source a pour but d’identifier le champ d’excitation en mesurant la réponse du système. Pour l’Holographie acoustique de champ proche (Near-field Acoustic Holography), la réponse du système (pression acoustique rayonnée) est mesurée sur un hologramme bidimensionnel utilisant un réseau de microphones et le champ source (le champ de vitesse acoustique) est reconstruit par une technique de rétropropagation effectuée dans le domaine des nombres d’ondes. L’objectif des travaux présentés est d’utiliser le même type de techniques pour reconstruire le champ de déplacement sur toute la surface d’une plaque en mesurant les vibrations sur des hologrammes à une dimension (lignes de mesures). Dans le domaine vibratoire, l’équation du mouvement de plaque implique la présence de 4 types d’ondes différents, deux étant purement évanescents. Ces derniers peuvent introduire des instabilités dans l’application de la méthode, notamment lorsque les hologrammes sont placés dans le champ lointain des efforts appliqués à la structure. La méthode présentée ici, appelée ”Holographie Vibratoire”, est particulièrement intéressante quand une mesure directe du champ de vitesse est impossible. L’holographie vibratoire permet également de séparer les sources dans le cas d’excitations multiples en les considérant comme des ondes allers ou retours. Il est alors possible d’isoler l’influence de chaque source et de quantifier notamment les champs d’intensités structurales que chacune d’elles génère. L’objectif de cette thèse est de présenter les principes de l’holographie Vibratoire, ses limites, ses applications et de les illustrer par des exemples sur plaque infinie, plaque appuyée et sur des résultats expérimentaux
The source field reconstruction aims at identifying the excitation field measuring the response of the system. In Near-field Acoustic Holography, the response of the system (the radiated acoustic pressure) is measured on a hologram using a microphones array and the source field (the acoustic velocity field) is reconstructed with a back-propagation technique performed in the wave number domain. The objective of the present works is to use such a technique to reconstruct displacement field on the whole surface of a plate by measuring vibrations on a one-dimensional holograms. This task is much more difficult in the vibratory domain because of the complexity of the equation of motion of the structure. The method presented here and called "Structural Holography" is particularly interesting when a direct measurement of the velocity field is not possible. Moreover, Structural Holography decreases the number of measurements required to reconstruct the displacement field of the entire plate. This method permits to separate the sources in the case of multi-sources excitations by considering them as direct or back waves. It’s possible to compute the structural intensity of one particular source without the contributions of others sources. The aim of this PHD is to present the principles of Structural Holography, its limits, its applications and illustrate them with examples of infinite plate, supported plate and on experimental results

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Kostrzewa, Krzysztof [Verfasser], and Manfred [Akademischer Betreuer] Aigner. "Advanced computational methods in identification of thermo-acoustic systems / Krzysztof Kostrzewa. Betreuer: Manfred Aigner." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2011. http://d-nb.info/1018421009/34.

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Uumati, Martha. "Acoustic investigations on bearded goby and jellyfish in the northern Benguela ecosystem." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/4469.

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Historically the nutrient rich Benguela ecosystem supported large stocks of commercially important fish which sustained the Namibian fishing sector. Recently, non-exploited species i.e. bearded goby (Sufflogobius bibarbatus) and jellyfish (Chrysaora fulgida and Aequorea forskalea) have become more apparent and are described as key-species in this ecosystem. Empirical evidence for understanding the stock abundance and dynamics of S. bibarbatus and jellyfish are still sparse, as research focus has been mainly on commercially important fish. The abundance of these non-exploited species in relation to the environment and commercial species are also not well understood. Lack of methods to effectively assess jellyfish and S. bibarbatus have furthermore limited our knowledge. Acoustics can cover large water volumes and observe many trophic groups and interactions simultaneously hence currently proposed as the most reliable observation tool available to remotely study multiple species that are overlapping and widely distributed in marine ecosystems. For acoustic assessments using echo sounders, the ability to detect, identify and distinguish targets from each other and the echo ability (target strength: TS) of individual targets is pivotal to convert acoustic data from a calibrated system into significant biological measures. The lack of effective acoustic identification (ID) techniques and knowledge about TS of species may limit the application of acoustics. The swimbladder generally contributes more than 90% to the backscattered energy from fish, which makes knowledge of the swimbladder vital for understanding the acoustic properties of a fish. Prior to this study, the presence or absence of a swimbladder within S. bibarbatus has been uncertain. This thesis is an exploratory study addressing 1) the acoustic identification challenge of species in aggregating in mixed assemblages and 2) the acoustic characteristics of the target species. The latter two are of essence to assess the biomass, distributions and ecological interactions of these non-exploited. The multiple frequency data (18, 38, 70, 120 and 200 kHz) and trawl data used in this study were collected on a survey conducted by the RV G.O.Sars during April 2008 in the northern Benguela. Fifteen validated assumed to be ‘single species' trawl and acoustic datasets were selected and used in the application and developing of ID techniques. Traditional acoustic identification techniques (Sᵥ-differencing and relative frequency response r(f)) were adopted and found ineffective as standalones to discriminate the species under study. The overlaps in the Sᵥ differences of the three species complicated separation. A multivariate statistical approach, Linear Discriminant Analysis (LDA) was applied to predict which of the variables s[subscript(A)], S[subscript(A)], Δs[subscript(A)] and r(f) discriminated the three species groups from each other with a higher accuracy. It was found that by combining backscattering strength S[subscript(A)] and r(f) a correct classification accuracy of up to 95% could be obtained. Limitation is that the LDA technique as any classification method is not applicable in “real time” during surveys. A new technique, here within referred to as the Separator Technique, which incorporates the standard techniques, LDA results, a novel r(f) similarity comparison technique and a threshold s[subscript(A)] response technique was established. The effectiveness of the Separator Technique is in the recognition of similarities and stability in frequency response by simple correlation of the observed frequency response at systematic Sᵥ-threshold levels. Accurate acoustic classification depends on good and valid training datasets and there has so far not been a simple way of acoustically detecting if the selected assumed “pure” datasets is contaminated or not. Only available reliable source are the trawl samples. The r(f) similarity comparison method showed that some of the assumed ‘single species' trawls were mixed and that presence of <1% of strong scatterers could mask a weaker scatterer. By evaluating the threshold s[subscript(A)] frequency response, the proportion of thresholded backscattering could be quantified. A frequency which is more appropriate for the acoustic assessment of the respective species in mixed aggregations could also be identified. Further improvements of the Separator Technique are required in terms of the precise Sᵥ-cut levels. The presence of S. bibarbatus' swimbladder was confirmed from two thawed specimens. From further investigations on 26 dissections of sampled S. bibarbatus, the swimbladder was identified as a physoclist (closed swimbladder) with an extensive gas gland, and its morphology was roughly described as prolate spheroid shaped and with about 5ᴼ negatively tilted compared fish vertebra. This means that the strongest echo from a goby will be found when the fish is at about 5ᴼ head down relative to the horizontal. The in situ TS of 8 cm sized S. bibarbatus and the two jellyfish species: C. fulgida [umbrella diameter: 21.7 cm] and A. forskalea [16 cm] at multiple frequencies (18, 38, 70, 120 and 200 kHz) was estimated. At 38 kHz, the TS was -53 dB for S. bibarbatus, -58 dB for A. forskalea and -66 dB for C. fulgida. The single echo detection (SED) approach which is assumed to be a more accurate method for estimating TS than the previously applied methods for jellyfish. The TS results for S. bibarbatus are of similar magnitude to other published TS values of C. fulgida. This suggests that estimates of jellyfish may be overestimated due to inaccuracies in target identification. This thesis established the acoustic characteristics of jellyfish and S. bibarbatus within the northern Benguela which makes it possible to acoustically assess and monitor jellyfish and/or fish. The identification technique though still in early phases of development, can be applied to enhance quality of training datasets (samples) used in classification. This piece of work can reduce variability in biomass estimates that arises from masking or misclassification of echoes.

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Farren, Maureen A. "Some experiments with underwater acoustic returns from cylinders relative to object identification for AUV operation/." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23398.

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Approved for public release; distribution is unlimited
Underwater Vehicles, Sonar Sound Analyzers, Underwater Navigation, Acoustics, Anechoic Chambers, Cylindrical Bodies, Data Storage Systems, Delay, Electroacoustic Transducers, Estimates, Experimental Data, Geometric Forms, Identification, Images, Position Location, Propagation, Sonar, Surface Properties, Target Strength, Theses, Time Intervals, Underwater, Underwater Equipment

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Abdou, Wael Saber Soliman. "Identification of acoustic emission sources in machinery : application to injection/combustion processes in diesel engines." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2979.

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The high temporal resolution of Acoustic Emission offers great promise in the on-line monitoring of complex machines such as diesel engines. The fuel injection process is one of the most important processes in the diesel engine and its timing and fuel delivery control are critical in combustion efficiency. In this work, the phenomena leading to the generation of acoustic emission during injection are investigated by simulation of the injection process in a specially designed rig and through test in running engines on a test-bed. Signal processing approaches are devised to produce diagnostic indicators for the quality of the injection process. The novelty of the research lies in; 1) obtaining a coherent set of data which allows the separation of the part of the signal associated with injection in a given cylinder from other sources adjacent in time and space, and 2) in developing a signal processing approach which allows this separation to be achieved on line using an array of sensors. As such, the research is generic to multi-source multi-sensor analysis in machines. A series of experiments were performed on an experimental injector rig, and two-stroke and four-stroke diesel engines under different operating conditions. The injector rig experiments provided useful information on the characteristic signatures of the injection events, finding which could be implemented to the more complex signal from the running engines. A number of sensor arrays (sets of two and three sensors) were used on two types of four-stroke engine at different running speeds to investigate the source identification of the injection events, the essential strategy being to add complexity to the information in the AE record by using engines of varying degrees of mechanical sophistication. It has been concluded that the AE signals are generated by the mechanical movements of the components in the pump and injector as well as aspects of the fuel flow through the injector and the piping. Also, it is found that the temporal structure of the AE is highly sensitive to sensor position, and that transmission path differences to a sensor array are generally large enough to allow source separation. Applying a purpose-designed thresholding technique, followed by canonical correlation allows the separate identification of parts of the AE signal in the short crank angle widow where sources involved in injection, inlet valve opening and combustion are operating.

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Cuneyitoglu, Ozkul Mine. "Acoustic Perception Through The Ground Interaction Of Compliant Legs Of A Hexapod Robot." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614028/index.pdf.

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A dynamically dexterous legged robot platform generates specific acoustic signals during the interaction with the ground and the environment. These acoustic signals are expected to contain rich information that is related to the interaction surface as a function of the position of the legs and the overall contact process mixed with the actuator sounds that initiate the movement. As the robot platform walks or runs in any environment, this convolved acoustic signal created can be processed and analyzed in real time operation and the interaction surface can be identified. Such an utilization of acoustic data can be possible for various indoor and outdoor surfaces and with this can be useful in adjusting gait parameters that play an essential role in dynamic dexterity. In this work, surface type identification is achieved with using the several popular signal processing and pattern classification methods not on the robot platform but off-line. The performances of the selected features and the algorithms are evaluated for the collected data sets and these outputs are compared with the expectations. Depending on the off-line training and experiment results, the applicability of the study to an embedded robot platform as a future application is found quite feasible and the surface type as an input to the robot sensing is expected to improve the mobility of the robot in both indoor and outdoor environment.

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Morrison, Archie Todd. "System identification and state reconstruction for autonomous navigation of an underwater vehicle in an acoustic net." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37999.

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Thesis (Ocean. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.
GRSN 683373
Includes bibliographical references (leaves 202-205).
by Archie Todd Morrison, III
Ocean.E.

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Nagl, Michael Martin. "Identification of the mechanism of oxide scale fracture, and its correlation with strain using acoustic emission." Thesis, University of South Wales, 1992. https://pure.southwales.ac.uk/en/studentthesis/identification-of-the-mechanism-of-oxide-scale-fracture-and-its-correlation-with-strain-using-acoustic-emission(60f7dec2-bf42-4f44-86f7-b216a1adc662).html.

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Thermally formed oxides scales can protect metals from aggressive environments at high temperatures. However the barrier function is destroyed when the oxide fails. Therefore a new 4-point bend test technique has been developed to measure the failure strains and to study the failure mechanisms of brittle layers in tension and compression. Tests were made with iron oxide and nickel oxide at room temperature and 550 or 900 °C, respectively, using strain rates of 10~* and 10"5 s"1 . Brittle lacquer was used as a model layer. Acoustic emission (AE) was employed to monitor and interpret failure mechanisms together with post test metallography. Equi-distant cracks were formed during failure in tension. Further cracking was affected by elastic and plastic stress relaxation processes, and interface delamination only started after these processes were exhausted. The crack spacing increased with oxide thickness and the results indicated that plastic relaxation processes were dominant at growth temperature conditions. The shear strength of the interface was lower at growth temperature. Shear failure within the layer was found in NiO and brittle lacquer when tested in compression. Failure in iron oxide under compression always started at the interface. The failure mechanism and initiation in compression was determined by the relative shear strength of interface, the shear strength of the layer and the buckling stability of the layer. However, spallation always required crack growth at the interface. Measured failure strains in tension and compression agreed well with the predictions of a model incorporating the fracture mechanics condition for tensile cracking or interface crack growth respectively and factors like residual strains, oxide creep and lateral oxide growth which accounted for the behaviour of a thin growing scale on a thick substrate. The critical fracture mechanics parameter in tension was the composite void size. A K1C value of ~ 1.1 MN nv3/2 was obtained for iron oxide for room temperature and 550 °C. Values of 0.41 and -1.61 MN m3/2 were found for NiO at room temperature and at 900 °C, respectively. The residual growth stresses in iron oxide were determined as approximately zero and the cooling strain from 550 °C was -0.05 - 0.06%. The residual stresses in NiO were -175 MPa at room temperature. The strain energy release rate for interfacial failure in iron oxide was 27 J m-2 and the fracture surface energies were 3.4 and 0.8 J m-2 for iron and nickel oxide, respectively. AE was a useful tool for explaining the failure mechanisms and a numerical analysis showed a slight difference in the AE signal released during tensile and compressive failure.

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Menon, Amrita Madhukumar. "The use of automated acoustic identification software for bat surveys in the neotropics : Gaps and opportunities." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/173540.

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As populações de morcegos são conhecidas por serem afetadas por atividades antropogênicas,njá que os Chiroptera é um grupo extremamente diverso que ocupa quase todos os nichos disponíveis no meio terrestre. Assim, os morcegos são considerados bons bioindicadores para monitorar mudanças no meio ambiente, mas seu valor como tal também depende da facilidade de monitorar e detectar tendências demográficas em suas populações. O interesse a longo prazo dos pesquisadores na acústica dos morcegos resulta do fato de que é um método não-invasivo e eficiente em termos de tempo para monitorar os padrões espaço-temporais da diversidade e atividade de morcegos. A análise dos sons emitidos pelos organismos tem sido útil para a aquisição de conhecimento sobre as interações bióticas e abióticas específicas de cada espécie, e sua aplicação na conservação. Além das identificações manuais de chamados de morcegos, existe atualmente no mercado um conjunto de programas automatizados de identificação que utilizam bibliotecas regionais e se apresentam como uma ferramenta eficiente no monitoramento de populações de morcegos. A maioria desses programas não foi validada usando dados de campo. Este estudo avalia a confiabilidade de dois softwares automatizados, SonoChiro e Kaleidoscope Pro, em comparação com identificações manuais de dados de campo coletados da região Neotropical. Houve um baixo nível de concordância entre os dois métodos automatizados ao nível das identificações específicas, razoável ao nível do gênero e satisfatório ao nível a família. Houve também uma diferença significativa entre a proporção de chamados corretamente identificados entre os dois programas ao nível específico. Os principais desafios para o uso de software de identificação automatizada incluem a necessidade de bibliotecas de chamados abrangentes da diversidade existente nas regiões em foco dos estudos; as principais oportunidades, por outro lado, incluem a ampla possibilidade de monitorar os padrões espaço-temporais da atividade de morcegos. Existem ainda fortes lacunas que impedem uma aplicação generalizada de programas automatizados em estudos ecológicos e de conservação de morcegos, mas há potencial de melhoria. Considerando as limitações dos programas automatizados, é discutida uma estrutura para aplicação em estudos ecológicos e de conservação.
Bat populations are known to be affected by anthropogenic activities because bats are an extremely diverse group occupying almost all available niches in terrestrial environment. Hence, bats are considered bioindicators to monitor changes in the environment, but their value as such also depends on the ease to monitor and detect demographic trends in their populations. The long term interest of researchers in the acoustic of bats results from the fact that it is a non-invasive, time-efficient methods to monitor spatiotemporal patterns of bat diversity and activity.The analysis of sounds emitted by organisms has been considered useful to gain insight into species-specific biotic and abiotic interactions, which can further be applied to conservation. Besides manual identifications of bat calls, a number of automated species identification programs using regional call classfiers have been introduced into the market as an efficient tool in monitoring of bat populations. Most of these programs have not been validated using field data. This study evaluates the reliability of two automated softwares, SonoChiro and Kaleidoscope Pro, in comparison to manual identifications of field data collected from the Neotropical region. There was low agreement between the two automated methods at the species level, fair agreement at the genus level and moderate agreement at the family level. There was also a significant difference between the proportion of correctly identified calls of the two-automated software at the species level identifications. Major challenges for using automated identification software include the need for comprehensive call libraries of the regions under scope; major opportunities, on the other hand, include the widespread possibility to monitor spatiotemporal patterns of bat activity. Overall, there are serious gaps that preclude a widespread application of automated programs in ecological and conservation studies of bats, but there is a potential for improvement. Considering the limitations of the automated programs, a framework for application in ecological and conservation studies is discussed.

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Goodwin, Katy Rebecca. "Bat Population Monitoring in National Parks of The Great Lakes Region and Evaluation of Bat Acoustic Analysis Software." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31570.

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North American bats face multiple threats, prompting an increase in bat research and conservation efforts in recent decades. Researchers often use acoustic monitoring, which entails recording bats? echolocation calls and subsequently identifying them to species, typically using automated software. Chapter 1 describes an acoustic monitoring program at eight U.S. national parks that aims to assess changes in bat populations over time. Data collected in 2016-2017 showed that activity levels of the little brown bat (Myotis lucifigus) decreased significantly while other species remained stable. Little brown bats have undergone similar population declines elsewhere due to the disease white-nose syndrome. Chapter 2 investigates whether different versions of bat call identification software are comparable to each other and how accurate they are. For the two software programs tested, agreement among versions was variable and species-dependent. Furthermore, newer versions were more conservative in assigning identifications, though not, on average, more accurate.

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Janos, Gregg A. "Utilizing Acoustic Methods to Identify Bat Species, and to Assess Their Habitat Use and Perception of Owls." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1363428258.

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Meesala, Vamsi Chandra. "Nonlinear Effects in Contactless Ultrasound Energy Transfer Systems." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/101752.

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Ultrasound acoustic energy transfer (UAET) is an emerging contactless technology that offers the capability to safely and efficiently power sensors and devices while eliminating the need to replace batteries, which is of interest in many applications. It has been proposed to recharge and communicate with implanted medical devices, thereby eliminating the need for invasive and expensive surgery and also to charge sensors inside enclosed metal containers typically found in automobiles, nuclear power plants, space stations, and aircraft engines. In UAET, energy is transferred through the reception of acoustic waves by a piezoelectric receiver that converts the energy of acoustic waves to electrical voltage. It has been shown that UAET outperforms the conventional CET technologies that use electromagnetic waves to transfer energy, including inductive coupling and capacitative coupling. To date, the majority of research on UAET systems has been limited to modeling and proof-of-concept experiments, mostly in the linear regime, i.e., under small levels of acoustic pressure that result in small amplitude longitudinal vibrations and linearized piezoelectricity. Moreover, existing models are based on the "piston-like" deformation assumption of the transmitter and receiver, which is only accurate for thin disks and does not accurately account for radiation effects. The linear models neglect nonlinear effects associated with the nonlinear acoustic wave propagation as well as the receiver's electroelastic nonlinearities on the energy transfer characteristics, which become significant at high source strengths. In this dissertation, we present experimentally-validated analytical and numerical multiphysics modeling approaches aimed at filling a knowledge gap in terms of considering resonant acoustic-piezoelectric structure interactions and nonlinear effects associated with high excitation levels in UAET systems. In particular, we develop a reduced-order model that can accurately account for the radiation effects and validate it by performing experiments on four piezoelectric disks with different aspect ratios. Next, we study the role of individual sources of nonlinearity on the output power characteristics. First, we consider the effects of electroelastic nonlinearities. We show that these nonlinearities can shift the optimum load resistance when the acoustic medium is fluid. Next, we consider the nonlinear wave propagation and note that the shock formation is associated with the dissipation of energy, and as such, shock formation distance is an essential design parameter for high-intensity UAET systems. We then present an analytical approach capable of predicting the shock formation distance and validate it by comparing its prediction with finite element simulations and experimental results published in the literature. Finally, we experimentally investigate the effects of both the nonlinearity sources on the output power characteristics of the UAET system by considering a high intensity focused ultrasound source and a piezoelectric disk receiver. We determine that the system's efficiency decreases, and the maximum voltage output position drifts towards the source as the source strength is increased.
Doctor of Philosophy
Advancements in electronics that underpinned the development of low power sensors and devices have transformed many fields. For instance, it has led to the innovation of implanted medical devices (IMDs) such as pacemakers and neurostimulators that perform life-saving functions. They also find applications in condition monitoring and wireless sensing in nuclear power plants, space stations, automobiles and aircraft engines, where the sensors are enclosed within sealed metal containers, vacuum/pressure vessels or located in a position isolated from the operator by metal walls. In all these applications, it is desired to communicate with and recharge the sensors wirelessly. Such a mechanism can eliminate the need for invasive and expensive surgeries to replace batteries of IMDs and preserve the structural integrity of metal containers by eliminating the need for feed through wires. It has been shown that ultrasound acoustic energy transfer (UAET) outperforms conventional wireless power transfer techniques. However, existing models are based on several assumptions that limit their potential and do not account for effects that become dominant when a higher output power is desired. In this dissertation, we present experimentally validated numerical and theoretical investigations to fill those knowledge gaps. We also provide crucial design recommendations based on our findings for the efficient implementation of UAET technology.

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LEE, JOON-HYUN. "DEVELOPMENT OF NEW TECHNIQUE FOR DAMPING IDENTIFICATION AND SOUND TRANSMISSION ANALYSIS OF VARIOUS STRUCTURES." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin985028187.

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Bousabaa, Sofiane. "Acoustic Green’s Function Estimation using Numerical Simulations and Application to Extern Aeroacoustic Beamforming." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS228.

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Les techniques d’identification acoustique visent à caractériser les différentes sources de bruit sur un avion à partir de données microphoniques. Ces techniques nécessitent la connaissance de la fonction de Green acoustique du milieu. Or celle-ci n’est connue analytiquement que pour des configurations simples et l’utilisation de fonctions de Green imparfaites conduit à une erreur sur l’identification des sources. L’objectif de cette thèse est de mettre au point une méthode numérique d’estimation des fonctions de Green pour l’imagerie aéroacoustique. La méthode doit avoir un coût de calcul minimal et fournir une estimation suffisamment précises pour être utilisée dans des configurations réalistes. Pour cela, la parcimonie de la fonction de Green dans le domaine temporel est prise en compte. Il en découle un problème d’identification de système nécessitant l’utilisation d’algorithmes de régression linéaire. La méthode est d’abord validée sur des cas numériques 3D représentatifs de ceux rencontrés dans l’industrie. Lorsque le nombre de points de focalisation est élevé, la réciprocité en écoulement retourné simplifie considérablement le problème. La méthode est ensuite appliquée sur des données d’essais réalisés sur une aile à haute portance passée en soufflerie anéchoïque à veine ouverte justifiant de l’applicabilité de la méthode sur des configurations industrielles réalistes
Acoustic imaging techniques aims at characterizing the different acoustic sources of noise on an aircraft using microphone array measurements. Those techniques require the knowledge of the acoustic Green’s function of the medium. Unfortunately, this function is known only for cases of relatively simple complexity and the use of approximate Green’s function can lead to errors in the identification of the sources. The main aim of this thesis is to set up a numerical method for the estimation of the Green’s function for aeroacoustic imaging applications. The method must have a minimal computational cost and provide a sufficiently accurate estimation to be used on realistic industrial configurations. The proposed methodology takes advantage of the sparsity of the Green’s functions in the time-domain. This results in a system identification problem and sparsity-based regression algorithms can be used to solve it. First, the method is validated on complex 3D numerical test cases typical of those encountered in the industry. For configurations involving a high number of focus points, the reverse-flow reciprocity simplifies significantly the Green’s function estimation problem. The methodology is finally applied on high lift 2D wing data placed in the ONERA CEPRA19 open section anechoic wind tunnel justifying the applicability of the method on realistic industrial configurations

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Cousson, Rémi. "Identification de sources acoustiques au passage d'un véhicule routier par imagerie acoustique parcimonieuse dans le domaine temporel." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI106/document.

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Le présent travail de recherche s'inscrit dans le cadre de la caractérisation de l'émission de bruit des véhicules routiers. On désire identifier les sources de bruit d'un véhicule en mouvement, lors de son passage sur une voie de circulation en conditions réelles, à partir de mesures acoustiques effectuées à poste fixe en bord de voie. Les méthodes d'imagerie acoustique utilisées actuellement présentent des performances insuffisantes sur véhicules routiers. Un état de l'art a permis d’identifier une méthode existante, MSA-PSF, consistant à effectuer sous certaines hypothèses une déconvolution sur sources mobiles dans le domaine fréquentiel, et originellement utilisée en aéronautique. Cette méthode est ici adaptée au contexte des véhicules routiers. Dans un deuxième temps, une approche originale est introduite pour répondre spécifiquement aux contraintes de ce contexte : CLEANT. Il s’agit d’une méthode itérative, dans le domaine temporel avec une approche large bande, qui prend en compte les effets du déplacement des sources et qui comporte deux paramètres permettant d’affiner les résultats : le facteur de boucle et le critère d’arrêt. Une version filtrée en fréquence est également proposée et montre une amélioration de l’identification de sources secondaires dans certains cas. CLEANT présente l’avantage d’obtenir des signaux-sources temporels reconstruits, ouvrant la voie à d’autres analyses, en particulier l’utilisation de la cohérence avec des signaux issus de mesures embarquées pour la séparation des contributions de sources décorrélées. MSA-PSF et CLEANT sont évaluées sur des simulations numériques à l'aide d'indicateurs mesurant leurs performances sur les aspects localisation et quantification de sources. Elles sont par la suite testées expérimentalement en conditions contrôlées de laboratoire, par l'utilisation d'une source mobile. Cette expérience permet une première application à un cas pratique, impliquant un mouvement linéaire, la présence de deux sources simultanées et des signaux de différentes natures (tonale et large bande). Enfin, elles sont comparées à l’approche classique de formation de voies sur source mobile, dans le cadre d’une expérience avec véhicule en conditions réelles. L'approche originale CLEANT fournit des résultats très encourageants, représentant une amélioration de la formation de voies classique, notamment en basse fréquence sur les cas testés. L'application à un véhicule en conditions réelles illustre certains comportements potentiellement problématiques de CLEANT et les solutions apportées par sa version filtrée en fréquence ou par l'ajustement de ses différents paramètres. Un premier test des approches par référencement avec des signaux issus de mesures embarquées est également présenté pour discriminer l'origine physique des sources, et souligne l'incidence de la brièveté des signaux inhérente au contexte de sources au passage
The study detailed in this manuscript is part of the effort to characterize the noise emission from road vehicles. We wish to identify the noise sources of a moving vehicle, when driven on a roadway in real-world conditions, with roadside acoustic measurements. The current acoustic imaging methods do not provide sufficient performance on road vehicles. A state of the art led to the selection of an existing method, MSA-PSF, which consists in deconvolving signals from mobile sources in the frequency domain under certain assumptions, and was originally developed for aeroacoustics. This method is adapted here to the context of road vehicles. Then, an original approach is proposed in order to tackle the specific constraints of this context: CLEANT. This is an iterative method, performed in time domain with a wideband approach, which takes into account the effect of sources motion and includes two parameters designed to refine the result: the loop factor and the stopping criterium. A further version of the algorithm, including a frequency filter, is also proposed and shows significant improvement in identifying secondary sources in some particular cases. An interesting point of CLEANT is the availability of the sources reconstructed time signals, which enables other types of analysis, especially the use of the coherence with signals from on-board measurements in order to separate the contributions of uncorrelated sources. MSA-PSF and CLEANT are evaluated with numerical simulations and a set of indicators to measure their source localization and quantification performance. They are then tested in a controlled laboratory conditions experiment, using a moving source. This experiment represents a first application of the methods to a practical case, involving a linear motion, two simultaneous sources and different kinds of signals (tone and wideband). They are finally compared to the classical approach of moving source beamforming, within the frame of an experiment on a road vehicle, in real-world conditions. The original approach CLEANT yields very encouraging results, and is a clear improvement from the conventional beamforming, especially at low frequency for the tested cases. Applying it to a road vehicle in real-world conditions highlights a potentially troublesome behavior of the method, and the solution brought by CLEANT's frequency filtered version, or by adapting its various parameters. The coherence with reference signals to discriminate the physical origins of the sources is also tested and underlines the role of the short duration of the signals related to the sources passing-by context

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Cellier, Antony Hermann Guy. "Detection and Identification of Instability and Blow-off/Flashback Precursors in Aeronautical Engines using Deep Learning techniques." Thesis, KTH, Kraft- och värmeteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-272079.

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The evolution of injection processes toward more fuel efficient and less polluting combustion systems tend to make them more prone to critical events such as Thermo-Acoustic Instabilities, Blow-Off and Flash-Back. Moreover, the addition of Di-Hydrogen as a secondary or as the main fuel is in discussion by aeronautical engines manufacturers. It drastically modifies the stability of the system and thus raise several interrogations concerning the multiplicity of its use. Being able to predict critical phenomena becomes a necessity in order to efficiently operate a system without having to pre-test every configuration and without sacrificing the safety of the user. Based on Deep Learning techniques and more specifically Speech Recognition, the following study presents the steps to develop a tool able to successfully detect and translate precursors of instability of an aeronautical grade swirled injector confined in a tubular combustion chamber. The promising results obtained lead to proposals for future transpositions to real-size systems.
Utvecklingen av injektionsprocesser mot mer bränsleeffektiva och mindre förorenande förbränningssystem, tenderar att göra dem mer benägna att utsättas för kritiska händelser som Thermo-Acoustic Instabilities, Blow-Off och Flash-Back. Dessutom diskuterar flygmotorkonstruktörer möjligheten att använda Dihydrogen som sekundärt eller som huvudbränsle. Det modifierar drastiskt systemets stabilitet och det väcker frågan hur man kan använda det effektivt. Att kunna förutsäga kritiska fenomen blir en nödvändighet för att använda ett system utan att behöva att på förhand testa varje konfiguration och utan att reducera användarens säkerhet. Baserat på Deep-Learning-tekniker och Speech-Recognition-tekniker, presenterar följande studie stegen för att utveckla ett verktyg som kan upptäcka och översätta föregångare till instabilitet hos en swirled flygmotorerinsprutningspump som är innesluten i en förbränningskammare. De lovande resultaten leder till idéer om hur man kan anpassa det här verktyg till ett system i verklig storlek.

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Grialou, Matthieu. "Vibro-acoustics substructuring : Combining simulations and experimental identification of subdomains for low frequency vehicle acoustics." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI109/document.

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La sonorité de l’échappement joue un rôle significatif sur le confort acoustique des occupants, ainsi que sur le caractère du véhicule. L’étude proposée porte sur la problématique industrielle suivante : « Description et quantification de la transmission du son entre la bouche d’échappement et l’intérieur du véhicule ». Physiquement la transmission sonore entre l’échappement et l’intérieur du véhicule s’effectue en trois étapes : Propagation des ondes sonores de la canule à la surface extérieure du véhicule et conversion en énergie vibratoire (1) ; Le bruit structurel se propage de la peau extérieure du véhicule à l’habillage intérieur (2) ; La surface intérieure du véhicule rayonne de l’énergie dans l’air à l’intérieur (3). Dans l’état de l’art proposé, la méthode de sous-structuration vibro-acoustique Patch Transfer Functions (PTF) est considérée comme une alternative viable à la problématique proposée. Cependant, avant d’appliquer la méthode sur un véhicule complet, la problématique suivante devait être résolue : « Caractérisation expérimentale d’un sous-système par des mesures sur un système couplé ». Ce manuscrit propose une méthode originale pour mesurer des fonctions de transfert d’un système découplé, sur la base de la réponse d’un système couplé. En raison de la nature mal posée du problème inverse, une méthode originale de régularisation a été proposée. La méthode a été validée pas des essais numériques, puis par un test physique
Exhaust noise has a significant impact on acoustic comfort and the sound identity of a vehicle brand. The present study focuses on the: “Description and quantification of the sound transmission from the exhaust outlet into the interior of a vehicle”. Physically the noise propagation from the exhaust pipe to the cabin consists of three steps: The sound waves propagate through the air from the exhaust outlet to the external skin of the vehicle (1); the external skin vibrates and transmits its vibration to the internal skin (2); the internal skin radiates sound in the passengers’ cabin (3). The Patch Transfer Functions method, which is based on the framework of dynamic substructuring, allows for the consideration of this complex problem as simpler subproblems that consist of subsystem interactions. Yet the application of the method to a full vehicle requires addressing the problem: “Characterization of Patch Transfer Functions of a subsystem by means of measurement on a coupled system”. This dissertation presents an original inverse method for the measurement of Patch Transfer Functions. In industrial structures, this in-situ characterization is generally the only possible measurement method. Yet, due to the ill posed nature of the problem, the inversion process is difficult. An original regularization method is proposed. The method is tested through numerical simulations, and is validated with an experimental setup

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Le, Magueresse Thibaut. "Approche unifiée multidimensionnelle du problème d'identification acoustique inverse." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI010.

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La caractérisation expérimentale de sources acoustiques est l'une des étapes essentielles pour la réduction des nuisances sonores produites par les machines industrielles. L'objectif de la thèse est de mettre au point une procédure complète visant à localiser et à quantifier des sources acoustiques stationnaires ou non sur un maillage surfacique par la rétro-propagation d'un champ de pression mesuré par un réseau de microphones. Ce problème inverse est délicat à résoudre puisqu'il est généralement mal-conditionné et sujet à de nombreuses sources d'erreurs. Dans ce contexte, il est capital de s'appuyer sur une description réaliste du modèle de propagation acoustique direct. Dans le domaine fréquentiel, la méthode des sources équivalentes a été adaptée au problème de l'imagerie acoustique dans le but d'estimer les fonctions de transfert entre les sources et l'antenne, en prenant en compte le phénomène de diffraction des ondes autour de l'objet d'intérêt. Dans le domaine temporel, la propagation est modélisée comme un produit de convolution entre la source et une réponse impulsionnelle décrite dans le domaine temps-nombre d'onde. Le caractère sous-déterminé du problème acoustique inverse implique d'utiliser toutes les connaissances a priori disponibles sur le champ sources. Il a donc semblé pertinent d'employer une approche bayésienne pour résoudre ce problème. Des informations a priori disponibles sur les sources acoustiques ont été mises en équation et il a été montré que la prise en compte de leur parcimonie spatiale ou de leur rayonnement omnidirectionnel pouvait améliorer significativement les résultats. Dans les hypothèses formulées, la solution du problème inverse s'écrit sous la forme régularisée de Tikhonov. Le paramètre de régularisation a été estimé par une approche bayésienne empirique. Sa supériorité par rapport aux méthodes communément utilisées dans la littérature a été démontrée au travers d'études numériques et expérimentales. En présence de fortes variabilités du rapport signal à bruit au cours du temps, il a été montré qu'il est nécessaire de mettre à jour sa valeur afin d'obtenir une solution satisfaisante. Finalement, l'introduction d'une variable manquante au problème reflétant la méconnaissance partielle du modèle de propagation a permis, sous certaines conditions, d'améliorer l'estimation de l'amplitude complexe des sources en présence d'erreurs de modèle. Les développements proposés ont permis de caractériser, in situ, la puissance acoustique rayonnée par composant d'un groupe motopropulseur automobile par la méthode de la focalisation bayésienne dans le cadre du projet Ecobex. Le champ acoustique cyclo-stationnaire généré par un ventilateur automobile a finalement été analysé par la méthode d'holographie acoustique de champ proche temps réel
Experimental characterization of acoustic sources is one of the essential steps for reducing noise produced by industrial machinery. The aim of the thesis is to develop a complete procedure to localize and quantify both stationary and non-stationary sound sources radiating on a surface mesh by the back-propagation of a pressure field measured by a microphone array. The inverse problem is difficult to solve because it is generally ill-conditioned and subject to many sources of error. In this context, it is crucial to rely on a realistic description of the direct sound propagation model. In the frequency domain, the equivalent source method has been adapted to the acoustic imaging problem in order to estimate the transfer functions between the source and the antenna, taking into account the wave scattering. In the time domain, the propagation is modeled as a convolution product between the source and an impulse response described in the time-wavenumber domain. It seemed appropriate to use a Bayesian approach to use all the available knowledge about sources to solve this problem. A priori information available about the acoustic sources have been equated and it has been shown that taking into account their spatial sparsity or their omnidirectional radiation could significantly improve the results. In the assumptions made, the inverse problem solution is written in the regularized Tikhonov form. The regularization parameter has been estimated by an empirical Bayesian approach. Its superiority over methods commonly used in the literature has been demonstrated through numerical and experimental studies. In the presence of high variability of the signal to noise ratio over time, it has been shown that it is necessary to update its value to obtain a satisfactory solution. Finally, the introduction of a missing variable to the problem reflecting the partial ignorance of the propagation model could improve, under certain conditions, the estimation of the complex amplitude of the sources in the presence of model errors. The proposed developments have been applied to the estimation of the sound power emitted by an automotive power train using the Bayesian focusing method in the framework of the Ecobex project. The cyclo-stationary acoustic field generated by a fan motor was finally analyzed by the real-time near-field acoustic holography method

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Young, Kathryn. "Identification and Estimation of Sensitive Life History Parameters for Cetaceans in Response to Acoustic Disturbances with Implications for Conservation." NSUWorks, 2008. http://nsuworks.nova.edu/occ_stuetd/238.

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Meta-analyses of published cetacean life history data and original modeling efforts have been conducted to determine which vital rates are most important in determining the growth and sustainability of both odontocete and mysticete populations. In particular, the role of anthropogenic sound in the ocean was examined in relation to cetacean population trends, with specific implications for life functions, vital rates, and population sustainability. Elasticity and sensitivity analyses of Leslie matrices suggested that most cetacean populations appear to be most sensitive to changes in the adult female survival rate, and least sensitive to calf survival. A secondary factor to which whale populations are sensitive is a change in juvenile survival or growth. With the exception of the North Atlantic right whale (Eubalaena glacialis), most cetaceans are not sensitive to changes in fecundity at any age stage. Of particular concern for depleted cetacean species, adult females may be sensitive to changes in foraging success which limit their ability to acquire sufficient body fat to reproduce and raise calves successfully. These results are similar to those for other species with similar life histories, such as terrestrial vertebrates and non-mammalian marine predators. The resulting model outputs have direct implications for the management of marine mammals, particularly in regions where acoustic disturbances are likely in the future or are currently prevalent. Additionally, information gained from these modeling exercises may aid in the transition of the Population Consequences of Acoustic Disturbances (PCAD) model from qualitative to quantitative, as well as provide useful values for the parameterization of population viability analyses (PVAs) in cetacean management. The implications of these model findings to cetacean conservation are many, and include: 1) Increases in anthropogenic noise in the marine environment which have the capacity to limit adult female survival should be avoided at all costs, 2) Due to the inexact nature of cetacean population modeling, changes in vital rates may induce undetectable or unpredictable changes in population growth rate, so use of the precautionary principle is strongly advised in management decisions, 3) There are likely thresholds within which population vital rates can change without a resulting change in the growth rate, but these are not indicated by traditional sensitivity and elasticity analyses. Future studies are needed focusing on the likely intricate relationships between anthropogenic ocean noise and both adult female and juvenile cetacean survival. Additionally, improvements in cetacean modeling resulting in more precise and robust population and vital rate estimates would prove invaluable to the conservation of these species.

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Faber, Benjamin Mahonri. "Active Minimization of Acoustic Energy Density in a Mock Tractor Cab." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/129.

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An active noise control (ANC) system has been applied to the problem of attenuating low-frequency tonal noise inside small enclosures. The intended target application of the system was the reduction of the engine firing frequency inside heavy equipment cabins. The ANC system was based on a version of the filtered-x LMS adaptive algorithm, modified for the minimization of acoustic energy density (ED), rather than the more traditional minimization of squared acoustic pressure (SP). Three loudspeakers produced control signals within a mock cabin composed of a steel frame with plywood sides and a Plexiglas® front. An energy density sensor, capable of measuring acoustic pressure as well as acoustic particle velocity, provided the error signal to the control system. The ANC system operated on a single reference signal, which, for experiments involving recorded tractor engine noise, was derived from the engine's tachometer signal. For the low frequencies at which engine firing occurs, experiments showed that ANC systems minimizing ED and SP both provided significant attenuation of the tonal noise near the operator's head and globally throughout the small cabin. The tendency was for ED control to provide a more spatially uniform amount of reduction than SP control, especially at the higher frequencies investigated (up to 200 Hz). In dynamic measurement conditions, with a reference signal swept in frequency, the ED control often provided superior results, struggling less at frequencies for which the error sensor was near nodal regions for acoustic pressure. A single control channel often yielded performance comparable to that of two control channels, and sometimes produced superior results in dynamic tests. Tonal attenuation achieved by the ANC system was generally in excess of 20 dB and reduction in equivalent sound level for dynamic tonal noise often exceeded 4 dB at the error sensor. It was shown that temperature changes likely to be encountered in practice have little effect on the initial delay through the secondary control path, and are therefore unlikely to significantly impact ANC system stability in the event that a fixed set of system identification filter coefficients are employed.

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Demontis, Hugo. "Identification de sources acoustiques complexes en milieu réverbérant par grands réseaux de microphones." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS196.

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La directivité d'une source sonore intervient dans de nombreuses applications en acoustique, allant de la compréhension des phénomènes physiques aéro-acoustiques jusqu'à la reproduction sonore spatialisée. Pour estimer expérimentalement cette signature spatiale, il est d’usage de déployer les microphones de sorte à englober partiellement ou totalement les sources. Le rayonnement acoustique est ainsi capté dans toutes les directions de l'espace. Sur ce principe, nous proposons dans ce manuscrit le développement d'un réseau microphonique 3D de grandes dimensions. L'antenne baptisée MODO ("Les Murs Ont Des Oreilles") comprend un total de 1024 MEMS digitaux, répartis sur les murs et les parois d'une salle rectangulaire classique. Pour localiser les sources acoustiques et caractériser leur directivité, nous résolvons le problème inverse associé sous contrainte de parcimonie structurée. La méthode choisie exploite le faible nombre de sources dans la salle, autorisant une représentation parcimonieuse du champ sonore mesuré. Le formalisme des harmoniques sphériques est utilisé pour décomposer efficacement la directivité des sources et les composantes élémentaires de rayonnement qui la compose. Les trajets de propagation acoustique sont modélisés via l'intégration des fonctions de transfert de la salle, qui sont synthétisées grâce au principe des antennes virtuelles. Nous validons la méthode de caractérisation proposée sur des sources directives connues, dont la directivité est étalonnée au préalable à l'aide d'une antenne sphérique d'ordre élevé
Knowing the directivity pattern of an acoustic source is useful in many applications in acoustics. To experimentally estimate the spatial signature, it is common to deploy microphones partially or totally surrounding the source. The acoustic radiation is then captured in all possible directions. In this thesis, we discuss the development of a large-scale 3D microphone array. This array, named "MODO" ("Les Murs Ont Des Oreilles", or, "The Walls Have Ears"), is comprised of 1024 digital MEMS microphones, flush mounted on the walls and the ceiling of a typical shoe-box room. In order to localize the sources and identify their directivity pattern, we solve the associated inverse problem under block-sparsity constraints. The chosen method exploits the small number of sources inside the room, allowing a sparse representation of the measured sound field. We use the spherical harmonics formalism to efficiently describe the directivity of the sources and their individual contributions to the radiation pattern. The acoustic path is modelled via integration of room transfer functions, synthesized with the mirror microphone method. We validated the proposed characterization method \textit{in situ} by comparison with known directivity patterns, calibrated using a high order spherical microphone array in controlled conditions

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Burnett, Stephen C. "Individual variation in the echolocation calls of Big Brown Bats (Eptesicus fuscus) and their potential for acoustic identification and censusing /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486394475981357.

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Udeigwe, Lawrence C. "Identification of objects in an acoustic waveguide numerical results and an introduction to an alternate approach via the method of images /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.51 Mb., 34 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:.

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Buot, de l’Épine Yorick. "Identification de l’impédance d’un traitement en présence d’un écoulement." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2369/document.

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Afin de réduire les bruits rayonnés en sortie de guide d’onde, des traitements acoustiques localement réactifs, comme les structures « Plaque perforée/Nid d’abeilles », peuvent être appliqués en liner. La conception de ces liners devient alors un challenge important avec l’apparition de nouvelles normes sur le bruit et impose de posséder une très bonne connaissance du comportement de ces traitements, en particulier leur impédance de surface. Néanmoins, la caractérisation de cette impédance n’est pas une chose facile et est généralement réalisée via des modèles semi-empiriques comme ceux de Guess, Elnady, Allam ou expérimentalement par des méthodes de mesures directes ou inverses. Ces approches inverses permettent, par la confrontation d’une modélisation du problème avec des observations expérimentales, de retourner, au travers d’une fonction coût, l’impédance du traitement. Ces méthodes ont l’avantage de réaliser une observation dans les conditions réelles d’utilisation du traitement. En effet, de nombreux paramètres influencent l’impédance de surface comme la présence d’un écoulement, l’incidence de l’onde… Dans cette thèse, une méthode d’identification de l’impédance est proposée. A partir de l’impédance de surface d’un traitement « Plaque perforée/Nid d’abeille » prédite par un modèle empirique via ses paramètres géométriques (épaisseur de la plaque, diamètre des perforations…), une méthode basée sur l’approche Bayésienne est implémentée afin de remonter à l’impédance réelle du traitement. Le problème étudié consiste en la propagation d’une onde dans un tronçon rectangulaire traité sur sa face supérieure et la mesure des pressions acoustiques est réalisée sur le banc d’essai de l’Université Technologique de Compiègne avec un écoulement rasant. Un modèle de propagation d’ondes dans le conduit est développé via la technique du raccordement modal, afin de prédire la pression aux positions des microphones pour n’importe quelle valeur d’impédance. A partir de la mesure et de la simulation, la règle de Bayes peut être appliquée afin de construire la densité de probabilité a posteriori. Cette densité de probabilité est alors échantillonnée au travers d’un algorithme Évolutionnaire de Monte Carlo par Chaîne de Markov (EMCMC). L’intérêt principale de cette méthode, est d’obtenir de nombreuses d’informations statistiques sur les paramètres caractérisant l’impédance de surface comme leur distribution et leur corrélation
Locally reactive acoustic liners such as honeycomb structures with perforated panels can be modeled with a surface impedance in standard numerical models. However, the characterization of this impedance is not always straightforward. Empirical models or standing wave tube measurements are generally used to get the behavior of these acoustic treatments. Unfortunately, these methods provide only an evaluation of the impedance under specific conditions. Moreover, the conditions of use can change significantly the acoustic liners behavior as grazing flow conditions or oblique incident waves. A characterization of locally reactive acoustic liners is presented here. Starting from a set of parameters and represents a surface impedance using empirical model, an inverse method based on Bayesian approach is used to return the surface impedance taking in consideration the real conditions of use. A rectangular duct treated by a liner on its upper face is considered and these conditions are similar to the experiment present at the Université de Technologie de Compiègne. This inverse method requires a direct model to predict the pressure at some microphone positions with any surface impedance. The model used in the following is based on the Mode-Matching method. From the direct analytical model, the Bayes'rule is then used to get the posterior probability density function of the estimated impedance. An Evolutionary Monte Carlo by Markov chain (EMCMC) method is used to sample this posterior probability density. This method provides not only the best set of parameters but also some statistical information for each parameter

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Harris, Elizabeth A. "Detection and Identification of Marine Mammals in Passive Acoustic Recordings from SCORE using a Visual Processing Approach Established for HARP Data." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/7354.

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A visual processing approach developed for analyzing passive acoustic recordings of marine mammal vocalizations collected on a High-frequency Acoustic Recording Package (HARP) is applied to acoustic data collected through three hydrophones at the Southern California Offshore Range (SCORE) on a Naval Postgraduate School recording system. Temporally overlapping datasets collected in proximity to one another are examined with the expectation that vocalizations from species that normally inhabit this region (resident or transient) were recorded on both systems. The analysis process relies on determination of invariant and distinctive features of marine mammal vocal elements to classify mammal sources. Vocalization features used to identify specific sources in the HARP data appear modified in the SCORE data. We examine how the technical components and recording parameters of the SCORE recording system affect the received acoustic signatures of odontocetes to determine how the visual processing protocols applied to HARP data can be adapted for application to SCORE data.

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Grisel, Yann. "Localisation de défauts et applications pour les milieux inhomogènes en propagation d'ondes acoustiquesDefects localization and applications to inhomogeneous media in acoustic scattering." Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00675217.

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Cette thèse traite de problèmes inverses en propagation d'ondes acoustiques pour des milieux inhomogènes avec des mesures en champ lointain. Dans la première partie nous nous intéressons à la localisation de défauts, c'est-à-dire à la recherche du lieu où l'indice effectif est différent d'un indice de référence. Nous obtenons une caractérisation du support des défauts à partir des mesures par une extension de la "Factorization Method" d'A. Kirsch. Nous proposons plusieurs méthodes numériques permettant de déterminer la localisation des défauts dont une permettant de traiter le cas de directions d'émission et de réception distinctes. Ces algorithmes sont validés numériquement. Dans une seconde partie, nous considérons la reconstruction des valeurs d'un indice inconnu. A partir de la méthode de localisation de défauts introduite précédemment, nous proposons deux stratégies pour déterminer des zones d'intérêt sur lesquelles la reconstruction est focalisée. Enfin, nous introduisons un nouveau type de fonction coût pour la reconstruction, qui exploite les propriétés établies dans la première partie.

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Nocera, Tomas. "Assessing the Long-term Impacts of White-nose Syndrome on Bat Communities Using Acoustic Surveys at Fort Drum Military Installation." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95937.

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With declines in abundance and changing distribution of White-nose Syndrome (WNS)-affected bat species, increased reliance on acoustic monitoring is now the new "normal". As such, the ability to accurately identify individual bat species with acoustic identification programs has become increasingly important. Additionally, how bat distribution and habitat associations have changed at the local to sub-landscape scale in the post WNS environment is important to understand. The significance of these changes, relative to bat activity, may be based on the species-specific susceptibility to WNS. We used data collected from Fort Drum Military Installation, New York from the summers of 2003-2017 to analyze the accuracy of acoustic software programs, and assess the changes in relative bat activity, occupancy, and distribution induced by WNS. Our results indicate that continued acoustic monitoring of bat species, such as the little brown bat (Myotis lucifugus) in the Northeast, to assess ongoing temporal and spatial changes, habitat associations, and as a guide to direct future mist-netting should rely more on relative activity as the metric of choice. Furthermore, the continuous spread of WNS across North America will have strong negative effects on bat populations and communities, this study points to how individual species (both impacted and non-impacted) will respond to WNS. We believe that our results can help users choose automated software and MLE thresholds more appropriate for their needs to accurately address potential changes in communities of bat species due to impacts of WNS or other factors.
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Dissertations / Theses on the topic 'Acoustic identification'

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