Thematische Bibliographien / Acoustic field prediction

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Auswahl der wissenschaftlichen Literatur zum Thema „Acoustic field prediction“

Autor: Grafiati

Veröffentlicht am 28. Juni 2021

Zuletzt aktualisiert am 1. Februar 2022

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Zeitschriftenartikel zum Thema "Acoustic field prediction"

Yang, Da, und Cheuk Ming Mak. „A combined sound field prediction method in small classrooms“. Building Services Engineering Research and Technology 42, Nr. 4 (20.02.2021): 375–88. http://dx.doi.org/10.1177/0143624421994229.

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In this paper, a new combination method for sound field prediction is proposed. An optimization approach based on the genetic algorithm is employed for optimizing the transition frequency of the combined sound field prediction method in classrooms. The selected optimization approach can identify the optimal transition frequency so that the combined sound field prediction can obtain more efficient and accurate prediction results. The proposed combined sound field prediction method consists of a wave-based method and geometric acoustic methods that are separated by the transition frequency. In low frequency domain (below the transition frequency), the sound field is calculated by the finite element method (FEM), while a hybrid geometric acoustic method is employed in the high frequency domain (above the transition frequency). The proposed combined prediction models are validated by comparing them with previous results and experimental measurements. The optimization approach is illustrated by several examples and compared with traditional combination results. Compared to existed sound field prediction simulations in classrooms, the proposed combination methods take the sound field in low frequencies into account. The results demonstrate the effectiveness of the proposed model. Practical applications: This study proposes a combined sound field prediction method separated by transition frequency. A genetic algorithm optimization method is employed for searching the optimal transition frequency. The outcomes of this paper are essential for acoustical designs and acoustical environmental assessments.

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Jierula, Alipujiang, Shuhong Wang, Tae-Min OH und Pengyu Wang. „Study on Accuracy Metrics for Evaluating the Predictions of Damage Locations in Deep Piles Using Artificial Neural Networks with Acoustic Emission Data“. Applied Sciences 11, Nr. 5 (05.03.2021): 2314. http://dx.doi.org/10.3390/app11052314.

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Accuracy metrics have been widely used for the evaluation of predictions in machine learning. However, the selection of an appropriate accuracy metric for the evaluation of a specific prediction has not yet been specified. In this study, seven of the most used accuracy metrics in machine learning were summarized, and both their advantages and disadvantages were studied. To achieve this, the acoustic emission data of damage locations were collected from a pile hit test. A backpropagation artificial neural network prediction model for damage locations was trained with acoustic emission data using six different training algorithms, and the prediction accuracies of six algorithms were evaluated using seven different accuracy metrics. Test results showed that the training algorithm of “TRAINGLM” exhibited the best performance for predicting damage locations in deep piles. Subsequently, the artificial neural networks were trained using three different datasets collected from three acoustic emission sensor groups, and the prediction accuracies of three models were evaluated with the seven different accuracy metrics. The test results showed that the dataset collected from the pile body-installed sensors group exhibited the highest accuracy for predicting damage locations in deep piles. Subsequently, the correlations between the seven accuracy metrics and the sensitivity of each accuracy metrics were discussed based on the analysis results. Eventually, a novel selection method for an appropriate accuracy metric to evaluate the accuracy of specific predictions was proposed. This novel method is useful to select an appropriate accuracy metric for wide predictions, especially in the engineering field.

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Semiletov, Vasily A., und Sergey A. Karabasov. „Similarity scaling of jet noise sources for low-order jet noise modelling based on the Goldstein generalised acoustic analogy“. International Journal of Aeroacoustics 16, Nr. 6 (September 2017): 476–90. http://dx.doi.org/10.1177/1475472x17730457.

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As a first step towards a robust low-order modelling framework that is free from either calibration parameters based on the far-field noise data or any assumptions about the noise source structure, a new low-order noise prediction scheme is implemented. The scheme is based on the Goldstein generalised acoustic analogy and uses the Large Eddy Simulation database of fluctuating Reynolds stress fields from the CABARET MILES solution of Semiletov et al. corresponding to a static isothermal jet from the SILOET experiment for reconstruction of effective noise sources. The sources are scaled in accordance with the physics-based arguments and the corresponding sound meanflow propagation problem is solved using a frequency domain Green’s function method for each jet case. Results of the far-field noise predictions of the new method are validated for the two NASA SHJAR jet cases, sp07 and sp03 from and compared with the reference predictions, which are obtained by applying the Lighthill acoustic analogy scaling for the SILOET far-field measurements and using an empirical jet-noise prediction code, sJet.

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Miller, SAE, und Alexander N. Carr. „Theoretical investigation of alteration and radiation of large-scale structures due to jet impingement“. International Journal of Aeroacoustics 18, Nr. 2-3 (20.12.2018): 231–57. http://dx.doi.org/10.1177/1475472x18812810.

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Jet flows impinge on launch pad structures and aircraft carrier deck blast deflectors. Turbulent structures are deformed and acoustic radiation is reflected by the deflector. The coupling of reflected acoustic waves with the instability waves of the jet turbulence increases their amplitude and causes a feedback loop. Resultant far-field acoustic radiation is amplified. This amplification results in additional tones with significant spectral broadening occurring at frequencies corresponding to the constructive interference. We present a simple prediction methodology in the form of an acoustic analogy. The analogy accounts for reflected acoustic waves through a tailored Green’s function and models the large-scale structures as spatially and temporarily growing and decaying instability waves. The predictions are compared with two experimental datasets. Predictions compare favorably with measured frequencies and spectral broadening in the far-field.

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Zhong, Siyang, und Xin Zhang. „A sound extrapolation method for aeroacoustics far-field prediction in presence of vortical waves“. Journal of Fluid Mechanics 820 (08.05.2017): 424–50. http://dx.doi.org/10.1017/jfm.2017.219.

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Off-surface integral solutions to an inhomogeneous wave equation based on acoustic analogy could suffer from spurious wave contamination when volume integrals are ignored for computation efficiency and vortical/turbulent gusts are convected across the integration surfaces, leading to erroneous far-field directivity predictions. Vortical gusts often exist in aerodynamic flows and it is inevitable their effects are present on the integration surface. In this work, we propose a new sound extrapolation method for acoustic far-field directivity prediction in the presence of vortical gusts, which overcomes the deficiencies in the existing methods. The Euler equations are rearranged to an alternative form in terms of fluctuation variables that contains the possible acoustical and vortical waves. Then the equations are manipulated to an inhomogeneous wave equation with source terms corresponding to surface and volume integrals. With the new formulation, spurious monopole and dipole noise produced by vortical gusts can be suppressed on account of the solenoidal property of the vortical waves and a simple convection process. It is therefore valid to ignore the volume integrals and preserve the sound properties. The resulting new acoustic inhomogeneous convected wave equations could be solved by means of the Green’s function method. Validation and verification cases are investigated, and the proposed method shows a capacity of accurate sound prediction for these cases. The new method is also applied to the challenging airfoil leading edge noise problems by injecting vortical waves into the computational domain and performing aeroacoustic studies at both subsonic and transonic speeds. In the case of a transonic airfoil leading edge noise problem, shocks are present on the airfoil surface. Good agreements of the directivity patterns are obtained compared with direct computation results.

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Salin, M. B., und D. A. Kosteev. „Nearfield acoustic holography-based methods for far field prediction“. Applied Acoustics 159 (Februar 2020): 107099. http://dx.doi.org/10.1016/j.apacoust.2019.107099.

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Gao, Sheng Yao, und De Shi Wang. „An Indirect Boundary Element Method for Computing Sound Field“. Advanced Materials Research 476-478 (Februar 2012): 1173–77. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.1173.

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Computing sound field from an arbitrary radiator is of interest in acoustics, with many significant applications, one that includes the design of classical projectors and the noise prediction of underwater vehicle. To overcome the non-uniqueness of solution at eigenfrequencies in the boundary integral equation method for structural acoustic radiation, wave superposition method is introduced to study the acoustics. In this paper, the theoretical backgrounds to the direct boundary element method and the wave superposition method are presented. The wave superposition method does not solve the Kirchoff-Helmholtz integral equation directly. In the approach a lumped parameter model is estabiled from spatially averaged quantities, and the numerical method is implemented by using the acoustic field from a series of virtual sources which are collocated near the boundary surface to replace the acoustic field of the radiator. Then the sound field over the of a pulsating sphere is calculated. Finally, comparison between the analytical and numerical results is given, and the speed of solution is investigated. The results show that the agreement between the results from the above numerical methods is excellent. The wave superposition method requires fewer elements and hence is faster, which do not need as high a mesh density as traditionally associated with BEM.

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Tao, Jun, Gang Sun, Ying Hu und Miao Zhang. „Noise Prediction for Multi-Element Airfoil Based on FW-H Equation“. Applied Mechanics and Materials 52-54 (März 2011): 1388–93. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1388.

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In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

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Lebon, Bruno, Iakovos Tzanakis, Koulis Pericleous und Dmitry Eskin. „Numerical Modelling of the Ultrasonic Treatment of Aluminium Melts: An Overview of Recent Advances“. Materials 12, Nr. 19 (06.10.2019): 3262. http://dx.doi.org/10.3390/ma12193262.

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The prediction of the acoustic pressure field and associated streaming is of paramount importance to ultrasonic melt processing. Hence, the last decade has witnessed the emergence of various numerical models for predicting acoustic pressures and velocity fields in liquid metals subject to ultrasonic excitation at large amplitudes. This paper summarizes recent research, arguably the state of the art, and suggests best practice guidelines in acoustic cavitation modelling as applied to aluminium melts. We also present the remaining challenges that are to be addressed to pave the way for a reliable and complete working numerical package that can assist in scaling up this promising technology.

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de Souza, Mauricy Cesar R., und Samir N. Y. Gerges. „Prediction of Sound Level in Rooms and Experimental Validation“. Building Acoustics 4, Nr. 2 (Juni 1997): 117–35. http://dx.doi.org/10.1177/1351010x9700400204.

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Traditional Sabine equations still are used for factories or offices where diffuse sound fields rarely occur and prediction can be inaccurate. More recently, methods based on geometric acoustics have been developed which require large computing time and which demand better defined input data. A problem, often encountered, is how to include input data which is appropriate, accurate and relatively easy to obtain. Three acoustic models of a furnished room were created: a diffuse field, an image source and a ray tracing model. The initial values of absorption coefficient and sound power level were obtained by standard measurements and the sound propagation SP was predicted and compared with measurement for each model. Then, the models were calibrated by altering the input parameters in order to minimise the difference between predicted and measured values. Sound pressure level due to two sources was also predicted and compared with measurement. For the room studied, the precision of the predictions, after calibration, is similar for the three models considered, with an average difference between simulated and measured values of less than 2 dB. Without the calibration procedure, the ray-tracing model gave the most precise first estimate. The diffuse and image source models needed significant modification of the input data to obtain a similar precision. The sound field in the room chosen for this study was nearly diffuse and simulation, based on geometric acoustics, did not offer clear advantages. However, this will not be the case for rooms with more complicated geometrical and acoustic characteristics such as in factories and offices. In addition, the image source model will not be appropriate for internal fittings which are much more complex than in the present study and an appropriate estimate of the scattering cross-section is problematical. In the ray tracing model, this problem is circumvented by incorporating the fittings as part of the geometry of the room.

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Dissertationen zum Thema "Acoustic field prediction"

Kücükcoskun, Korcan. „Prediction of free and scattered acoustic fields of low-speed fans“. Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00758274.

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This thesis proposes to predict the sound emitted from low-speed fans and its scattered-field by installation effects related to industrial applications. Both tonal and broadband components of fan noise are investigated. Methods existing in the literature contain assumptions and simplifications in order to deal with fan noise problems in analytical manner, such as consideration of an observer located in the far-field of the source. Firstly, the effect of far-field assumption in the tonal fan noise formulation is addressed. Using artificial blade sources, a comparison between two closed-form analytical solutions and a numerical technique is performed for validation in free-field. Secondly, the scattered field of the tonal fan noise is investigated using numerical and analytical techniques. The acoustic field of a rotor operating in a finite duct is first investigated combining the closed-form analytical formulations with the Boundary Element Method (BEM). Since BEM would be computationally demanding for high frequency applications, analytical scattering techniques are also introduced. Reflection and scattering of sound waves by a large plane are first addressed replacing the plane with an image source. Secondly, an exact analytical solution considering scattering of the tonal fan noise by a rigid corner is derived. Another point addressed in this thesis is the prediction of the broadband noise generated by a low-speed axial fan operating in turbulent stream. Amiet's theory of turbulence-interaction noise for a stationary air foil is considered. One of the key points proposed in this thesis is an extension of Amiet's method, allowing prediction of the acoustic field of the airfoil in its geometrical near-field in a semi-analytical perspective. The extended formulation is compared with Amiet's classical solution and a reference solution obtained with numerical integration involving no geometrical far-field assumption. Experiments are also performed in anechoic chamber using an isolated airfoil located in grid generated turbulence. Another assumption made in Amiet's theory is the consideration of uniform flow impinging onto the airfoil. However this assumption is not valid for most industrial applications. Different methods exist in literature to deal with this problem. A new approach is proposed in order to take the span wise varying flow conditions into account. Including all the improvements, the broadband acoustic responses of a stationary airfoil located in the developing region of a jet and of a low-speed axial fan operating in a turbulent stream are investigated and validated against measurements. Finally, scattering of the sound generated by the considered airfoil and fan by benchmark obstacles is addressed numerically and analytically. Since BEM is not capable to handle statistical source fields directly, an innovative approach obtained by re-formulating the deterministic BEM method is employed. The final model is compared to the numerical, analytical and experimental solutions for validation purposes.

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Majvald, František. „Metody akustické holografie v blízkém poli v prostředí LabVIEW“. Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442539.

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Near-field acoustical holography is a standard method for sound source visualization and localization. In this thesis, commonly used and newly published near-field acoustic holography methods are introduced and analysed. In addition, regularization methods are presented together with finding options of optimal regularization parameter. Based on theory, a LabVIEW library is built containing four implemented near-field acoustical holography algorithms and two regularization methods. To verify the correctness of implementations, a testing application has been made. This application allows testing of implemented algorithms with simulated or experimentally measured data. The correctness of implementation is verified, and algorithms are compared to each other with respect to accuracy and speed of calculation.

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Chan, Gary Ka-Yue. „Prediction of low-frequency sound-pressure fields in fitted rooms for active noise control“. Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/214.

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Low-frequency noise is a health concern for workers in industrial workshops; rooms of highly varying size and dimensions, usually containing obstacles (the ‘fittings’). Low-frequency noise can be generated from sources such as reciprocating or rotating machinery, or ventilation systems. As the exposure time to the noise lengthens, workers are increasingly at risk to harmful effects such as hearing loss, communication difficulty, personal discomfort, and even nausea from induced body vibrations. Passive methods of noise control, such as absorption or barriers, generally perform better at high frequencies, but are inadequate at low frequencies. A proposed solution is active noise control, which relies on destructive interference of sound waves to reduce noise levels. However, this depends on phase, and how it is affected when sound waves encounter diffracting obstacles. In addition, the geometrical configuration of the active-control system must be optimized, which can be done using a prediction model. Sound-prediction models can also estimate the decibel level of sound within a given room configuration created by a source and the attenuation provided by the control system. Therefore, it is of interest to develop a model that predicts sound propagation in fitted rooms with phase. In this thesis, sound-pressure fields were investigated in rooms containing parallelepiped obstacles at low frequencies for which the wavelength is comparable to the obstacle dimensions. The geometric theory of diffraction (GTD) was used to model edge diffraction from an obstacle and, thus, the pressure field in shadow regions. A ray-tracing prediction model was improved to consider both the amplitude and phase of sound fields, and also the effects of edge diffraction. To validate the prediction model, experiments were performed in an anechoic chamber where a source and diffracting objects were located. In collaboration with Dr Valeau at the Université de Poitiers in France, a second model based on the finite element method (FEM) was used to compare prediction results. It was found that the phase depends mostly on the direct unblocked source-to-receiver distance. The FEM and experimental results showed that occluding objects cause phase shifts. The implementation of first-order diffraction into the ray-tracing program was successful in predicting shadow zones, thus producing a better prediction of realistic sound fields in rooms with obstacles.

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Wang, Yuebing. „The application of optical interferometry to the measurement and prediction of focused acoustic fields“. Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/33661.

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High-Intensity Focused Ultrasound (HIFU) has been applied as an acceptable therapeutic technique and various HIFU systems have achieved clinical approval for general use in numerous countries. To ensure that an HIFU system is used in a safe and reliable application, its acoustic field needs to be characterized accurately. However, the traditional methods mostly are based on hydrophones, these sensors are found short of sufficient temporal and spatial resolutions, especially, they can only tolerate small acoustic pressures. This work is concerned with the feasibility of optical interferometry in measuring focused acoustic fields and in predicting HIFU fields.

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Cousins, Owen Mathew. „Prediction of sound pressure and intensity fields in rooms and near surfaces by ray tracing“. Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/843.

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The health, safety, comfort and productivity of a room’s occupants is greatly influenced by the sound field within it. An acoustical engineer is often consulted during the design of a room to prevent or alleviate unwanted acoustical problems. Prediction models are often used to find the most cost-effective solution to a given acoustical problem. The accuracy of sound-field prediction varies with the particular model, as do the parameters predicted. Most models only predict sound-pressure levels. Many only predict energetic quantities, ignoring wave phase and, therefore, interference and modal effects in rooms. A ray-tracing model, capable of predicting sound-pressure level, reverberation time and lateral energy fraction was translated into MATLAB code and modified to increase accuracy by including phase. Modifications included phase effects due to path length travelled and phase changes imparted by surface reflections as described by complex reflection coefficients. Further modifications included predicting steady-state and transient sound-intensity levels, providing information on the direction of sound-energy flow. The modifications were validated in comparison with free-field theory and theoretical predictions of sound fields in the presence of a single surface. The complex reflection coefficients of four common building materials were measured using two methods—an impedance tube and the spherical-decoupling method. Using these coefficients, the modified program was compared with experimental data measured in configurations involving one or more surfaces made of these materials, in an anechoic chamber, a scale-model room, and a full-scale office space. Prediction accuracy in the anechoic chamber, and in the presence of a single reflecting surface, greatly improved with the inclusion of phase. Further comparison with full-scale rooms is required before the accuracy of the model in such rooms can be evaluated definitively.

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Wei, Jiangtao. „Modelling of fuselage/floor structures and associated cabin acoustics for the prediction of propeller induced interior sound fields“. Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361553.

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Zachariah, Cherian Renil. „Statistical Model for Predicting Multiple Sclerosis Cortical Lesion Detection Rates with Ultra High Field Imaging“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1293726279.

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Lee, Kyung Taek. „Evaluation of the computational validity of the image model in predicting the sound field in a wedge-shaped layer using acoustical reciprocity“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School; Available from the National Technical Information Service, 1991. http://edocs.nps.edu/npspubs/scholarly/theses/1991/Dec/91Dec_Lee.pdf.

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Thesis (M.S. in Engineering Acoustics) Naval Postgradaute School, December 1991.
Thesis advisor(s): Coppens, Alan B. ; Sanders, James V. "December 1991." Includes bibliographical references. Also available online.

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Pignier, Nicolas. „Predicting the sound field from aeroacoustic sources on moving vehicles : Towards an improved urban environment“. Doctoral thesis, KTH, Farkost och flyg, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205791.

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In a society where environmental noise is becoming a major health and economical concern, sound emissions are an increasingly critical design factor for vehicle manufacturers. With about a quarter of the European population living close to roads with heavy traffic, traffic noise in urban landscapes has to be addressed first. The current introduction of electric vehicles on the market and the need for sound systems to alert their presence is causing a shift in mentalities requiring engineering methods that will have to treat noise management problems from a broader perspective. That in which noise emissions need not only be considered as a by-product of the design but as an integrated part of it. Developing more sustainable ground transportation will require a better understanding of the sound field emitted in various realistic operating conditions, beyond the current requirements set by the standard pass-by test, which is performed in a free-field. A key aspect to improve this understanding is the development of efficient numerical tools to predict the generation and propagation of sound from moving vehicles. In the present thesis, a methodology is proposed aimed at evaluating the pass-by sound field generated by vehicle acoustic sources in a simplified urban environment, with a focus on flow sound sources. Although it can be argued that the aerodynamic noise is still a minor component of the total emitted noise in urban driving conditions, this share will certainly increase in the near future with the introduction of quiet electric engines and more noise-efficient tyres on the market. This work presents a complete modelling of the problem from sound generation to sound propagation and pass-by analysis in three steps. Firstly, computation of the flow around the geometry of interest; secondly, extraction of the sound sources generated by the flow, and thirdly, propagation of the sound generated by the moving sources to observers including reflections and scattering by nearby surfaces. In the first step, the flow is solved using compressible detached-eddy simulations. The identification of the sound sources in the second step is performed using direct numerical beamforming with linear programming deconvolution, with the phased array pressure data being extracted from the flow simulations. The outcome of this step is a set of uncorrelated monopole sources. Step three uses this set as input to a propagation method based on a point-to-point moving source Green's function and a modified Kirchhoff integral under the Kirchhoff approximation to compute reflections on built surfaces. The methodology is demonstrated on the example of the aeroacoustic noise generated by a NACA air inlet moving in a simplified urban setting. Using this methodology gives insights on the sound generating mechanisms, on the source characteristics and on the sound field generated by the sources when moving in a simplified urban environment.
I ett samhälle där buller håller på att bli ett stort hälsoproblem och en ekonomisk belastning, är ljudutsläpp en allt viktigare aspekt för fordonstillverkare. Då ungefär en fjärdedel av den europeiska befolkningen bor nära vägar med tung trafik, är åtgärder för minskat trafikbuller i stadsmiljö en hög prioritet. Introduktionen av elfordon på marknaden och behovet av ljudsystem för att varna omgivningen kräver också ett nytt synsätt och tekniska angreppssätt som behandlar bullerproblemen ur ett bredare perspektiv. Buller bör inte längre betraktas som en biprodukt av konstruktionen, utan som en integrerad del av den. Att utveckla mer hållbara marktransporter kommer att kräva en bättre förståelse av det utstrålade ljudfältet vid olika realistiska driftsförhållanden, utöver de nuvarande standardiserade kraven för förbifartstest som utförs i ett fritt fält. En viktig aspekt för att förbättra denna förståelse är utvecklingen av effektiva numeriska verktyg för att beräkna ljudalstring och ljudutbredning från fordon i rörelse. I denna avhandling föreslås en metodik som syftar till att utvärdera förbifartsljud som alstras av fordons akustiska källor i en förenklad stadsmiljö, här med fokus på strömningsgenererat ljud. Även om det aerodynamiska bullret är fortfarande en liten del av de totala bullret från vägfordon i urbana miljöer, kommer denna andel säkerligen att öka inom en snar framtid med införandet av tysta elektriska motorer och de bullerreducerande däck som introduceras på marknaden. I detta arbete presenteras en komplett modellering av problemet från ljudalstring till ljudutbredning och förbifartsanalys i tre steg. Utgångspunkten är beräkningar av strömningen kring geometrin av intresse; det andra steget är identifiering av ljudkällorna som genereras av strömningen, och det tredje steget rör ljudutbredning från rörliga källor till observatörer, inklusive effekten av reflektioner och spridning från närliggande ytor. I det första steget löses flödet genom detached-eddy simulation (DES) för kompressibel strömning. Identifiering av ljudkällor i det andra steget görs med direkt numerisk lobformning med avfaltning med hjälp av linjärprogrammering, där källdata extraheras från flödessimuleringarna. Resultatet av detta steg är en uppsättning av okorrelerade akustiska monopolkällor. Steg tre utnyttjar dessa källor som indata till en ljudutbredningsmodel baserad på beräkningar punkt-till-punkt med Greensfunktioner för rörliga källor, och med en modifierad Kirchhoff-integral under Kirchhoffapproximationen för att beräkna reflektioner mot byggda ytor. Metodiken demonstreras med exemplet med det aeroakustiska ljud som genereras av ett NACA-luftintag som rör sig i en förenklad urban miljö. Med hjälp av denna metod kan man få insikter om ljudalstringsmekanismer, om källegenskaper och om ljudfältet som genereras av källor när de rör sig i en förenklad stadsmiljö.

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Mhatre, Natasha. „The Prediction Of Field Cricket Phonotaxis In Complex Acoustic Environments“. Thesis, 2007. http://hdl.handle.net/2005/883.

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Animals detect, recognize and localize relevant objects in noisy, multi-source environments. Female crickets locate potential mates in choruses of simultaneously calling males using acoustic signals, a behaviour termed phonotaxis. The mechanisms underlying cricket phonotaxis are now understood across multiple levels: biophysical, neurobiological and behavioural. Phonotaxis has, however, rarely been tested in the complex real-world acoustic environments and no attempts have been made to predict acoustic orientation behaviour in these conditions despite our extensive understanding of its underlying mechanisms. In this thesis, I first characterized the acoustic environments faced by female crickets of the species Plebeiogryllus guttiventris in the field. Phonotaxis behaviour of females was then characterized under laboratory conditions using two sound sources. The data obtained were used to develop a simulation that predicted this behaviour. The predictions of the simulation were then tested against the phonotaxis behaviour of females in realistic, multi-source conditions in the field. My field studies of male behaviour showed that males of this species produced complex and variable songs in choruses where multiple males called simultaneously. The acoustic ranges of males in these choruses overlapped extensively and females performing phonotaxis in such choruses would hear multiple males simultaneously. The acoustic interactions of simultaneously calling males were also characterized for their timing relationships with each other and the changes they made to the temporal patterns of their songs. Males did not either synchronise or alternate their chirps, however they made changes to the temporal patterns of song in a way that is likely to make them more attractive to females. I then characterized the closed-loop walking phonotaxis behaviour of P. guttiventris females in the presence of two active sound sources playing conspecific song. Both the baseline and relative SPLs of the two speakers were systematically varied and female phonotactic paths were obtained. Females were found to preferentially approach louder songs. Several aspects of this behaviour were characterized, in particular orientation ability and motor behaviour under varied conditions of stimulus intensity. A stochastic simulation of closed-loop walking phonotaxis behaviour was developed using both current understanding of field cricket physiology and my data on closed-loop walking phonotaxis. The simulation was demonstrated to both qualitatively and quantitatively recapture female behaviour. It was also able to qualitatively recapture female behaviour in two previously published classical experiments in which the hearing of female crickets was disrupted. Female phonotaxis was then tested under real-world multi-source conditions. The behaviour of real females was compared to the predictions of the simulation. The simulation was found to recapture both female preference and phonotactic path forms at the population level. To my knowledge, this is the first study to both examine and successfully predict phonotaxis behaviour in complex real-world acoustic conditions.

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Bücher zum Thema "Acoustic field prediction"

Fan noise prediction system development: Source/radiation field coupling and workstation conversion for the acoustic radiation code. [Washington, DC: National Aeronautics and Space Administration, 1993.

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R, Moselle J., und United States. National Aeronautics and Space Administration., Hrsg. A hybrid numerical technique for predicting the aerodynamic and acoustic fields of advanced turboprops: Final report. Buffalo, N.Y: Arvin Calspan Advanced Technology Center, 1988.

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Leonid, Oliker, Biswas Rupak und Research Institute for Advanced Computer Science (U.S.), Hrsg. New computational methods for the prediction and analysis of helicopter noise. [Moffett Field, Calif.]: Research Institute for Advanced Computer Science, NASA Ames Research Center, 1996.

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United States. National Aeronautics and Space Administration, Hrsg. Prediction of sound fields in acoustical cavities using the boundary element method: A thesis submitted to the faculty of Purdue University. [Washington, DC: National Aeronautics and Space Administration, 1985.

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Buchteile zum Thema "Acoustic field prediction"

Kampanis, N. A. „Fast and Accurate Finite Element Methods for the Numerical Prediction of the Acoustic Field“. In Full Field Inversion Methods in Ocean and Seismo-Acoustics, 21–26. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-015-8476-0_4.

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Ewart, T. E., und S. A. Reynolds. „Experimental Ocean Acoustic Field Moments Versus Predictions“. In Ocean Variability & Acoustic Propagation, 23–40. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3312-8_2.

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Powers, John P., Benito Baylosis, Peter Gatchell und William Reid. „Experimental Comparison of Measured Ultrasound Pressure Fields with Theoretical Prediction“. In Acoustical Imaging, 51–56. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4419-8772-3_8.

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Rüttgers, Mario, Seong-Ryong Koh, Jenia Jitsev, Wolfgang Schröder und Andreas Lintermann. „Prediction of Acoustic Fields Using a Lattice-Boltzmann Method and Deep Learning“. In Lecture Notes in Computer Science, 81–101. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-59851-8_6.

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Abstract Using traditional computational fluid dynamics and aeroacoustics methods, the accurate simulation of aeroacoustic sources requires high compute resources to resolve all necessary physical phenomena. In contrast, once trained, artificial neural networks such as deep encoder-decoder convolutional networks allow to predict aeroacoustics at lower cost and, depending on the quality of the employed network, also at high accuracy. The architecture for such a neural network is developed to predict the sound pressure level in a 2D square domain. It is trained by numerical results from up to 20,000 GPU-based lattice-Boltzmann simulations that include randomly distributed rectangular and circular objects, and monopole sources. Types of boundary conditions, the monopole locations, and cell distances for objects and monopoles serve as input to the network. Parameters are studied to tune the predictions and to increase their accuracy. The complexity of the setup is successively increased along three cases and the impact of the number of feature maps, the type of loss function, and the number of training data on the prediction accuracy is investigated. An optimal choice of the parameters leads to network-predicted results that are in good agreement with the simulated findings. This is corroborated by negligible differences of the sound pressure level between the simulated and the network-predicted results along characteristic lines and by small mean errors.

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Mcdonald, B. Edward, Joe Lingevitch und Michael Collins. „Effects of Environmental Variability on Focused Acoustic Fields“. In Impact of Littoral Environmental Variability of Acoustic Predictions and Sonar Performance, 377–83. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0626-2_47.

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Uscinski, B. J. „Acoustic Scattering in Wave-Covered Shallow Water. The Coherent Field“. In Impact of Littoral Environmental Variability of Acoustic Predictions and Sonar Performance, 329–36. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0626-2_41.

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Lermusiaux, P. F. J., und C. S. Chiu. „Four-Dimensional Data Assimilation for Coupled Physical-Acoustical Fields“. In Impact of Littoral Environmental Variability of Acoustic Predictions and Sonar Performance, 417–24. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0626-2_52.

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Sturm, F., M. C. Pelissier und D. Fattaccioli. „Development of an Acoustic Field Predictor in a Three Dimensional Oceanic Environment“. In Full Field Inversion Methods in Ocean and Seismo-Acoustics, 63–68. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-015-8476-0_11.

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Stasiunas, Eric C., Matthew K. Raymer und Garrett D. Nelson. „Predicting Flight Environments with a Small-Scale, Direct-Field Acoustic Test Facility“. In Sensors and Instrumentation, Volume 5, 87–98. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-54987-3_10.

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Schütz, Daniel, und Holger Foysi. „Towards the Prediction of Flow and Acoustic Fields of a Jet-Wing-Flap Configuration“. In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 659–69. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-64519-3_59.

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Konferenzberichte zum Thema "Acoustic field prediction"

Wang, Yuebing. „Prediction of acoustic field radiated from focusing transducer“. In 2013 6th International Congress on Image and Signal Processing (CISP). IEEE, 2013. http://dx.doi.org/10.1109/cisp.2013.6743894.

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Yao, Weigang, Min Xu und Zhimin Chen. „LES Prediction of Flow and Acoustic Field of Free Jet“. In 14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-2973.

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Martins, Nelson, Paulo Felisberto und Sergio M. Jesus. „Acoustic field calibration for noise prediction: The CALCOM' 10 data set“. In OCEANS 2011 - SPAIN. IEEE, 2011. http://dx.doi.org/10.1109/oceans-spain.2011.6003539.

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Andersson, Niklas, Lars-Erik Eriksson und Lars Davidson. „LES Prediction of Flow and Acoustic Field of a Coaxial Jet“. In 11th AIAA/CEAS Aeroacoustics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2005. http://dx.doi.org/10.2514/6.2005-2884.

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Sharma, Sanjay, und Dennis Siginer. „Permeability Measurement of Orthotropic Fibers Under an Acoustic Force Field“. In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78567.

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Using the validated acoustic method of determining physical properties of porous materials, acoustical properties of the orthotropic medium is used to predict longitudinal and transverse permeability. Measurement of samples in the impedance tube is conducted using ASTM E 1050 for a frequency range of 50 Hz to 6.4 KHz. The acoustical method is shown to compute longitudinal and transverse permeability for various porosity levels. The method describes permeability prediction for carbon, glass and hybrid lay ups. Longitudinal permeability calculated from the absorption coefficient of sized and unsized fibers is found to be the same in contrast to the flow methods.

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Seto, Mae L., Rubens Campregher, Stefan Murphy und Julio Militzer. „Prediction of Ship Acoustic Signature Due to Fluid Flow“. In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43343.

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The contribution of flow noise to the radiated acoustic signature of CFAV Quest is of interest. Quest is the research ship used by Defence R&D Canada as a quiet platform. It is difficult to identify the flow noise component in an acoustic ranging so there is interest in predicting the flow noise as a first step towards extracting it from range measurements. Below propulsor cavitation inception speeds, machinery-induced noise dominates. While flow noise does not usually dominate in the presence of machinery-induced noise or propulsor cavitation, it is unclear what fraction of the total noise power flow noise constitutes. A direct numerical simulation for a complex ship geometry was impractical so an alternative approach was sought. An immersed boundary method was used to model the presence of the ship in the flow domain. The unsteady flow field was calculated using a finite volume method over an unstructured Cartesian grid. The flow field around Quest in straight and level flight was calculated at Reynolds numbers between 1.8×108 and 4.3×108, corresponding to a full-scale speed range of 4 to 10 knots. Results from such flow field predictions become the hydrodynamic sources in the integrals of Lighthill’s acoustic analogy to predict the far-field acoustic signature from the flow past the hull. These far-field predictions consist of computing the propagation and radiation of the hydrodynamic sources. This assumes noise generation and its propagation are decoupled. Under certain circumstances, knowledge of the predicted flow component helps to extract it from a standard acoustic ranging.

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Erwin, James P., und Neeraj Sinha. „Near and Far-Field Investigations of Supersonic Jet Noise Predictions Using a Coupled LES and FW-H Equation Method“. In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45210.

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The hot supersonic exhausts of gas turbine engines on military aircraft generate dangerously high noise levels. The noise levels associated with operating these engines are harmful to aircraft carrier deck personnel as well as detrimental to ship and aircraft structures. In this paper, the supersonic jet exhaust is simulated using Large Eddy Simulation (LES), and the Ffowcs Williams and Hawkings (FW-H) equation transforms the LES solution to an acoustic solution in the far-field. A Mach 1.5 laboratory jet test at United Technologies Research Center - Acoustics Research Tunnel is used as validation for the LES/FW-H method. A grid refinement study was performed with the objective of determining the requirements for accurate noise predictions. The finest grid resolution yields the best near and far-field acoustic prediction. A second LES/FW-H validation case is shown for a twin jet experiment that was performed in the anechoic chamber at University of Mississippi’s National Center for Physical Acoustics (NCPA). The LES/FW-H method is applied to the higher complexity heated twin jet with faceted nozzle profiles, demonstrating the applicability of the method over a wider range of flow regimes. The far-field noise prediction agrees very well with the NCPA experiment, including the prediction of broadband shock associated noise and jet screech.

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Stanko, T., D. B. Ingham, M. Fairweather und M. Pourkashanian. „Application of RANS and FWH Modelling to the Prediction of Noise From Round Jets“. In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59620.

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This paper focuses on the CFD modelling of the aerodynamic noise generated by a hot non-reacting turbulent jet. A commercial CFD code is used to model the aerodynamic flow as well as in providing noise calculations. The main advantage of using CFD is the relatively low cost of the computational prediction in comparison with alternative experimental investigations. In addition, the CFD simulations provide detailed information on the aerodynamic sources of noise at every point in a flow, something that is difficult to achieve experimentally. The accuracy of the noise predictions is highly dependent on the means used to simulate the turbulent flow field, as well as the acoustic model applied. In this paper different approaches to predicting both the turbulent flow and acoustic noise are studied. For the jet investigated, the accuracy of various modelling approach is assessed against available data, with particular attention placed on the use of RANS simulations for the flow field prediction coupled to the Ffowcs Williams-Hawkings acoustic model. The aim of this paper is to demonstrate the level of flow field and acoustic modelling required to provide accurate predictions of noise emissions from jets with a view to their ultimate application as an aeroacoustic tool that can be used in identifying components or surfaces that generate significant amounts of noise, thereby providing opportunities for early design changes to aircraft and gas turbine components.

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Kurbatskii, Konstantin A., Saravana Kumar und Hossam A. El-Asrag. „Numerical Prediction of Mean Flow and Acoustic Field of a Supersonic Impinging Jet“. In 52nd Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2014. http://dx.doi.org/10.2514/6.2014-0559.

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Shuming Chen, Dengfeng Wang, Ankang Zuo und Zhen Chen. „Exterior noise prediction of light duty truck based on near-field acoustic holography“. In 2010 2nd International Conference on Mechanical and Electrical Technology (ICMET). IEEE, 2010. http://dx.doi.org/10.1109/icmet.2010.5598345.

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Berichte der Organisationen zum Thema "Acoustic field prediction"

Muhlestein, Michael, und Carl Hart. Geometric-acoustics analysis of singly scattered, nonlinearly evolving waves by circular cylinders. Engineer Research and Development Center (U.S.), Oktober 2020. http://dx.doi.org/10.21079/11681/38521.

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Geometric acoustics, or acoustic ray theory, is used to analyze the scattering of high-amplitude acoustic waves incident upon rigid circular cylinders. Theoretical predictions of the nonlinear evolution of the scattered wave field are provided, as well as measures of the importance of accounting for nonlinearity. An analysis of scattering by many cylinders is also provided, though the effects of multiple scattering are not considered. Provided the characteristic nonlinear distortion length is much larger than a cylinder radius, the nonlinear evolution of the incident wave is shown to be of much greater importance to the overall evolution than the nonlinear evolution of the individual scattered waves.

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Lermusiaux, Pierre F. Quantifying, Predicting and Exploiting Environmental and Acoustic Fields and Uncertainties. Fort Belvoir, VA: Defense Technical Information Center, September 2009. http://dx.doi.org/10.21236/ada531379.

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