Dissertations / Theses on the topic 'Acoustic detector'

Bat populations across North America are either facing new threats from white-nose syndrome (WNS) and wind energy development or have already experienced precipitous declines. Accordingly, researchers and managers need to know how to best monitor bats to document population and distribution changes, as well as where to look for persisting populations. Landscape-scale WNS impacts to summer bat populations are not well understood, and although acoustic monitoring is commonly used to monitor these populations, there is limited information about differences among acoustic detectors and the implications to managers thereof. My objectives were to model the relationship between WNS impact, influence of available hibernacula, and environmental factors for summer nightly presence of three WNS-affected bats and to compare how multiple models of acoustic detectors perform in terms of detection probability and nightly recorded bat activity. I collected acoustic data from 10 study areas across Virginia, West Virginia, Ohio and Kentucky to describe changes in nightly presence of WNS-affected bat species during summer 2017. During the same period of time, I compared five types of acoustic detectors at Fort Knox, Kentucky. My results show the potential efficacy of using a WNS impact-year metric to predict summer bat presence, and highlight which environmental variables are relevant for large-scale acoustic monitoring. Additionally, my findings suggest that each of the detector types tested would suffice for most research and monitoring activities, but standardization of detector type within the scope of a project or study should be encouraged.
Master of Science
Bat populations across North America are either facing new threats from white-nose syndrome (WNS) and wind energy development or have already experienced devastating declines. Accordingly, wildlife biologists need to know how to best monitor bats to document population and distribution changes, as well as where to look for remaining populations. Landscape-scale WNS impacts to summer bat populations are not well understood, and although acoustic technology is commonly used to monitor these populations, there is limited information about differences among acoustic detectors and the implications to managers thereof. My objectives were to model the relationship between WNS impact, influence of available bat hibernation caves, and environmental factors for summer nightly presence of three WNS-affected bats and to compare how multiple models of acoustic detectors perform in terms of detection probability and nightly recorded bat activity. I collected acoustic data from 10 study areas across Virginia, West Virginia, Ohio and Kentucky to describe changes in nightly presence of WNS-affected bat species during summer 2017. During the same period of time, I compared five types of acoustic detectors at Fort Knox, Kentucky. My results show potential viability of a WNS impact-year metric to predict summer bat presence, and highlight which environmental variables are relevant for large-scale acoustic monitoring. Additionally, my findings suggest that each of the detector types tested would suit most research and monitoring activities, but standardization of detector type within the scope of a project or study should be encouraged.

[Truncated abstract] Advanced laser interferometer gravitational wave detectors require an extremely high optical power in order to improve the coupling between the gravitational wave signal and the optical field. This high power requirement leads to new physical phenomena arising from nonlinear interactions associated with radiation pressure. In particular, detectors with multi-kilometer-long arm cavities containing high density optical fields suffer the possibility of 3-mode opto-acoustic interactions. This involves the process where ultrasonic vibrations of the test mass cause the steady state optical modes to scatter. These 3-mode interactions induce transverse optical modes in the arm cavities, which then can provide positive feedback to the acoustic vibrations in the test masses. This may result in the exponential growth of many acoustic mode amplitudes, known as Parametric Instability (PI). This thesis describes research on 3-mode opto-acoustic interactions in advanced interferometric gravitational wave detectors through numerical investigations of these interactions for various interferometer configurations. Detailed analysis reveals the properties of opto-acoustic interactions, and their dependence on the interferometer configuration. This thesis is designed to provide a pathway towards a tool for the analysis of the parametric instabilities in the next generation interferometers. Possible techniques which could be helpful in the design of control schemes to mitigate this undesirable phenomenon are also discussed. The first predictions of parametric instability considered only single interactions involving one transverse mode and one acoustic mode in a simple optical cavity. ... In Chapter 6, I was able to make use of a new analytical model due to Strigin et al., which describes parametric instability in dual recycling interferometers. To make the solution tractable, it was necessary to consider two extreme cases. In the worst case, recycling cavities are assumed to be resonant for all transverse modes, whereas in the best cases, both recycling cavities are anti-resonant for the transverse modes. Results show that, for the worst case, parametric gain values as high as ~1000 can be expected, while in the best case the gain can be as low as ~ 3. The gain is shown to be very sensitive to the precise conditions of the interferometer, emphasising the importance of understanding the behaviour of the detectors when the cavity locking deviates from ideal conditions. Chapter 7 of this thesis contains work on the observation of 3-mode interactions in an optical cavity at Gingin, which confirms the analysis presented here, and also a paper which shows how the problem of 3-mode interactions can be harnessed to create new devices called opto-acoustic parametric amplifiers. In the conclusions in Chapter 8, I discuss the next important steps in understanding parametric interactions in real interferometers – including the need for more automated codes relevant to the design requirements for recycling cavities. In particular, it is pointed out how the modal structure of power and signal recycling cavities must be understood in detail, including the Gouy phase for each transverse mode, to be able to obtain precise predictions of parametric gain. This thesis is organised as a series of papers which are published or have been submitted for publication. Such writing style fills the condition for Ph.D. thesis at the University of Western Australia.

Este trabalho apresenta o desenvolvimento de dispositivos semicondutores utilizando óxidos de zinco e estanho. O primeiro dispositivo semicondutor estudado está relacionado ao desenvolvimento de sensores de pH a partir do efeito de campo, enquanto que o segundo consiste na utilização de ondas acústicas de superfície para o transporte de portadores voltados para o desenvolvimento de detectores de um único fóton. Primeiramente, esses materiais foram utilizados como membranas sensíveis a íons de hidrogênio. Para isso foram fabricados os dispositivos denominados EGFETs cujo princípio de funcionamento é semelhante ao ISFET. Foram desenvolvidos filmes de SnO2 obtidos a partir da rota Pechini e pela técncia Sol-gel com o objetivo de investigar a resposta elétrica do EGFET em função da concentração de íons de H+ . Os sensores fabricados pela técnica sol-gel não apresentaram respostas satisfatórias devido à presença de poros. Por outro lado, obtivemos uma sensibilidade de 33mV/pH para o EGFET desenvolvido a partir da rota Pechini com uma membrana calcinada à 400o C. Propusemos também a utilização do ZnO como um possível candidato a sensor de pH a partir do EGFET. A melhor resposta do EGFET (uma sensibilidade de 38mV/pH) foi alcançada com a utilização de filmes de ZnO aquecidos à temperatura de 150o C. Além dos dispositivos para a detecção de íons de H+ apresentamos uma nova abordagem para a detecção de um único fóton a partir da combinação de dispositivos utilizando ondas acústicas de superfície e os transistores de um único elétron. Basicamente os protótipos consistem em uma estrutura de várias camadas otimizadas para uma eficiente absorção de fótons, uma junção p-i-n utilizada para coleta de portadores, IDT para geração da SAW e guias metálicos para controle de portadores durante o transporte acústico. Os portadores são eficientemente transportados por uma distância de 100 mm com uma perda de 12 % para a melhor configuração. Nessas condições, a eficiência do dispositivo é de 75%.
This work presents the study and development of semiconductor devices base on tin and zinc oxides. The first device is related to the development of pH sensors based on field effect, while the second device uses surface acoustic waves for the transport of carriers related to a single photon detector device. Initially, the semiconductors were used as hydrogen ions sensing membranes. For that aim extended gate field effect transistors (EGFET) were developed. Their working principle is similar to the ion sensitive field effect transistor (ISFET). Through Pechini and sol-gel SnO2 thin films were obtained. The EGFET response to H+ ions was not optimal due to the presence of pores. Using Pechini, a response of 33mV/pH was obtained for the EGFET membrane calcinated at 400o C. The use of ZnO as sensing membrane was also investigated, and the best response was a sensibility of 38mV/pH) for a film heated up to 150o C. In addition to the EGFET structure, a new approach to a single photon detection is presented. This uses the combination of surface acoustic waves with a single electron transistor. Two prototypes were developed using a multi-layered structure optimized for photon absorption. Carriers are collected using a p-i-n structure. Inter-digital-transducers are used for surface acoustinc wave generation. Metallic guides are used to control the carriers during acoustic tranport. Carriers were efficiently transported over a length of 100 mm with a loss of 12 % for the best configuration. Under this optimized conditions, the efficiency of the device is 75%.

This thesis is dedicated to the development of new energy detectors employed in the detection of unknown signals in the presence of non-Gaussian and non-independent noise samples. To this end, an extensive study has been conducted on di erent energy detection structures, and novel techniques have been proposed which are capable of dealing with these problematic situations. The energy detector is proposed as an optimum solution to detect uncorrelated Gaussian signals, or as a generalized likelihood ratio test to detect entirely unknown signals. In both cases, the background noise must be uncorrelated Gaussian. However, energy detectors degrade when the noise does not ful ll these characteristics. Therefore, two extensions are proposed. The rst is the extended energy detector, which deals with the problem of non-Gaussian noise; and the second is the preprocessed extended energy detector, used when the noise also possesses non-independent samples. A generalization of the matched subspace lter is likewise proposed based on a modi cation of the Rao test. In order to evaluate the expected improvement of these extensions with respect to the classical energy detector, a signalto- noise ratio enhancement factor is de ned and employed to illustrate the improvement achieved in detection. Furthermore, we demonstrate how the uncertainty introduced by the unknown signal duration can decrease the performance of the energy detector. In order to improve this behavior, a multiple energy detector, based on successive subdivisions of the original observation interval, is presented. This novel detection technique leads to a layered structure of energy detectors whose observation vectors are matched to di erent intervals of signal duration. The corresponding probabilities of false alarm and detection are derived for a particular subdivision strategy, and the required procedures for their general application to other possible cases are indicated. The experiments reveal the advantages derived from utilizing this novel structure, making it a worthwhile alternative to the single detector when a signi cant mismatch is present between the original observation length and the actual duration of the signal.
Moragues Escrivá, J. (2011). New energy detector extensions with application in sound based surveillance systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11520
Palancia

Language Recognition is the problem of discovering the language of a spoken definitionutterance. This thesis achieves this goal by using short term acoustic information within a GMM-UBM approach.The main problem of many pattern recognition applications is the variability of problemthe observed data. In the context of Language Recognition (LR), this troublesomevariability is due to the speaker characteristics, speech evolution, acquisition and transmission channels.In the context of Speaker Recognition, the variability problem is solved by solutionthe Joint Factor Analysis (JFA) technique. Here, we introduce this paradigm toLanguage Recognition. The success of JFA relies on several assumptions: The globalJFA assumption is that the observed information can be decomposed into a universalglobal part, a language-dependent part and the language-independent variabilitypart. The second, more technical assumption consists in the unwanted variability part to be thought to live in a low-dimensional, globally defined subspace. In this work, we analyze how JFA behaves in the context of a GMM-UBM LR framework. We also introduce and analyze its combination with Support Vector Machines(SVMs).The first JFA publications put all unwanted information (hence the variability) improvemen tinto one and the same component, which is thought to follow a Gaussian distribution.This handles diverse kinds of variability in a unique manner. But in practice,we observe that this hypothesis is not always verified. We have for example thecase, where the data can be divided into two clearly separate subsets, namely datafrom telephony and from broadcast sources. In this case, our detailed investigations show that there is some benefit of handling the two kinds of data with two separatesystems and then to elect the output score of the system, which corresponds to the source of the testing utterance.For selecting the score of one or the other system, we need a channel source related analyses detector. We propose here different novel designs for such automatic detectors.In this framework, we show that JFA's variability factors (of the subspace) can beused with success for detecting the source. This opens the interesting perspectiveof partitioning the data into automatically determined channel source categories,avoiding the need of source-labeled training data, which is not always available.The JFA approach results in up to 72% relative cost reduction, compared to the overall resultsGMM-UBM baseline system. Using source specific systems followed by a scoreselector, we achieve 81% relative improvement.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Bats correspond to 20% of the extant mammal species and, with a few exceptions, use echolocation, a spacial orientation system based on emission and analysis of echoes from sound waves, generally ultrasounds. Echolocation was discovered in the 1940 s and since the 1970 s ultrasound detectors have been commercially available, allowing the investigation of several aspects of the natural history and ecology of bats. Passive acoustic monitoring has been frequently used in habitat use studies, predominantly in North America and Europe, by comparing the number of bat passes between different habitat types. This dissertation presents the first evaluation of the spacial and seasonal variation patterns in the activity of insectivorous bats in the Brazilian biome Pampa, in the state of Rio Grande do Sul. Since bat activity can vary according to habitat type, time of year and climatic conditions, the following hypotheses were tested: 1. bat activity varies between different types of habitat; 2. bat activity varies seasonally; 3. bat activity is influenced by temperature, humidity and wind speed. The acoustic samples were taken along fixed transects of 1500 meters, which were monitored monthly from April 2009 to March 2010. Five habitat types were sampled: eucalypts, stream, riparian forest, wetland and grassland. In each sample, the number of bat passes was obtained by using an ultrasound detector Pettersson D230. A total of 1183 bat passes were registered. Greater bat activity levels was observed along large eucalypts (1.93 bat passes/3min) and along a stream (1.61 bat passes/3 min). A riparian forest (0.94 bat passes/3 min) and a wetland area (0.61 bat passes/3 min) exhibited statistically equal levels of activity. Bat passes were fewer in grassland areas (0,16 bat passes/3 min). Bat activity was not correlated with abiotic factors. However, bat activity was significantly low in the colder season, winter, and was similar in autumn, spring and summer. The observed preference for vegetation borders and water courses agrees with reports from other countries and is attributed predominantly to the high prey abundance in these types of environments. Additionally, low activity in the winter is probably a response to the reduced availability of insects, and to lower temperatures. Our results indicate which areas of arboreal vegetation and water courses should be priorities for the conservation of bats and that alterations of these habitat types might negatively influence bat activity in the region
Os morcegos correspondem a 20% dos mam?feros atuais e, com poucas exce??es, apresentam ecolocaliza??o, um sistema de orienta??o espacial a partir da emiss?o e an?lise de ecos de ondas sonoras, geralmente ultrassons. A ecolocaliza??o foi descoberta na d?cada de 1940 e a partir de 1970 detectores de ultrassons tornaram-se comercialmente dispon?veis, permitindo a investiga??o de diversos aspectos sobre hist?ria natural e ecologia de morcegos. Monitoramentos ac?sticos passivos tem sido frequentemente utilizados em estudos de uso de h?bitat, principalmente na Am?rica do Norte e Europa, comparando-se diferentes locais quanto ao n?mero de vezes em que morcegos s?o detectados. A presente disserta??o apresenta a primeira avalia??o de padr?es espaciais e sazonais na atividade de quir?pteros inset?voros do Brasil, realizada no bioma Pampa, Estado do Rio Grande do Sul. Uma vez que a atividade de morcegos pode variar de acordo com o h?bitat, o per?odo do ano e condi??es clim?ticas, foram testadas as seguintes hip?teses: 1. a atividade de morcegos ? heterog?nea entre diferentes tipos de h?bitat; 2. a atividade apresenta varia??es sazonais; 3. a atividade ? influenciada pela temperatura, umidade e velocidade do vento. As amostragens ac?sticas foram realizadas em transectos fixos de 1500 metros, monitorados mensalmente de abril de 2009 a mar?o de 2010. Os transectos abrangeram cinco tipos de h?bitat: Eucaliptos, Mata Ciliar, Banhado, Canal e Campo. Em cada amostragem, foram obtidos o n?mero de registros de atividade com um detector de ultrassons Pettersson D230. No total, foram obtidos 1183 registros de atividade, sendo que os maiores n?veis de atividade de quir?pteros foram observados em ?rea de ?rvores de eucaliptos de grande porte (1,93 registros/3 min) e de um canal (1,61 registros/3 min). Em segundo lugar, a borda de uma mata ciliar (0,94 registros/3 min) e a margem de um banhado (0,61 registros/3 min) apresentaram n?veis estatisticamente equivalentes de atividade. As ?reas de campo foram menos utilizadas. A atividade de quir?pteros n?o apresentou correla??o com os fatores abi?ticos. Por?m, foi significativamente menor na esta??o mais fria, o inverno, e apresentou valores similares no outono, primavera e ver?o. A prefer?ncia por bordas de vegeta??o e cursos d??gua coincide com o documentado para outros pa?ses e ? atribu?da principalmente ? concentra??o de presas nestes tipos de ambiente. Do mesmo modo, a diminui??o da atividade no inverno ? provavelmente uma resposta ? menor disponibilidade de insetos, al?m das baixas temperaturas. Nossos dados indicam que ?reas de vegeta??o arb?rea e cursos d??gua s?o priorit?rias para a conserva??o de morcegos e que altera??es nestes tipos de h?bitat tendem a influenciar negativamente a atividade de morcegos na regi?o

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: G. Tong Zhou; Committee Co-Chair: Xiaoli Ma; Committee Member: David V. Anderson; Committee Member: James Stevenson Kenney; Committee Member: Liang Peng; Committee Member: William D. Hunt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This report discusses a method to detect divers in harbour environments usingpassive acoustic detection. The goal was to achieve as high detection as possiblewithout having too high false alarm rate. A short execution time was also desirable.By using the characteristic of an inhalation a band-pass filter was applied to the signalto improve the signal to noise ratio. After the filtering an energy estimation of thesignal was made. This energy estimation was later used in a frequency analysis, whichcould tell us if there were enough energy in the frequencies that correspond to adivers breathing frequency. If this energy exceeds a threshold the detector decidesthat there is a diver in the water. To get an acceptable amount of false alarms, thethreshold was set so that the energy of the breathing frequencies had to exceed 5% ofthe energy in the frequencies above the breathing frequencies. Using this method onour data we found that the detector succeeded in finding the diver and didn’t give usany false alarms.

L'activitat humana que té lloc en sales de reunions o aules d'ensenyament es veu reflectida en una rica varietat d'events acústics, ja siguin produïts pel cos humà o per objectes que les persones manegen. Per això, la determinació de la identitat dels sons i de la seva posició temporal pot ajudar a detectar i a descriure l'activitat humana que té lloc en la sala. A més a més, la detecció de sons diferents de la veu pot ajudar a millorar la robustes de tecnologies de la parla com el reconeixement automàtica a condicions de treball adverses. L'objectiu d'aquesta tesi és la detecció i classificació automàtica d'events acústics. Es tracta de processar els senyals acústics recollits per micròfons distants en sales de reunions o aules per tal de convertir-los en descripcions simbòliques que es corresponguin amb la percepció que un oient tindria dels diversos events sonors continguts en els senyals i de les seves fonts. En primer lloc, s'encara la tasca de classificació automàtica d'events acústics amb classificadors de màquines de vectors suport (Support Vector Machines (SVM)), elecció motivada per l'escassetat de dades d'entrenament. Per al problema de reconeixement multiclasse es desenvolupa un esquema d'agrupament automàtic amb conjunt de característiques variable i basat en matrius de confusió. Realitzant proves amb la base de dades recollida, aquest classificador obté uns millors resultats que la tècnica basada en models de barreges de Gaussianes (Gaussian Mixture Models (GMM)), i aconsegueix una reducció relativa de l'error mitjà elevada en comparació amb el millor resultat obtingut amb l'esquema convencional basat en arbre binari. Continuant amb el problema de classificació, es comparen unes quantes maneres alternatives d'estendre els SVM al processament de seqüències, en un intent d'evitar l'inconvenient de treballar amb vectors de longitud fixa que presenten els SVM quan han de tractar dades d'àudio. En aquestes proves s'observa que els nuclis de deformació temporal dinàmica funcionen bé amb sons que presenten una estructura temporal. A més a més, s'usen conceptes i eines manllevats de la teoria de lògica difusa per investigar, d'una banda, la importància de cada una de les característiques i el grau d'interacció entre elles, i d'altra banda, tot cercant l'augment de la taxa de classificació, s'investiga la fusió de les
sortides de diversos sistemes de classificació. Els sistemes de classificació d'events acústics
desenvolupats s'han testejat també mitjançant la participació en unes quantes avaluacions d'àmbit
internacional, entre els anys 2004 i 2006. La segona principal contribució d'aquest treball de tesi consisteix en el desenvolupament de sistemes de detecció d'events acústics. El problema de la detecció és més complex, ja que inclou tant la classificació dels sons com la determinació dels intervals temporals on tenen lloc. Es desenvolupen dues versions del sistema i es proven amb els conjunts de dades de les dues campanyes d'avaluació internacional CLEAR que van tenir lloc els anys 2006 i 2007, fent-se servir dos tipus de bases de dades: dues bases d'events acústics aïllats, i una base d'enregistraments de seminaris interactius, les quals contenen un nombre relativament elevat d'ocurrències dels events acústics especificats. Els sistemes desenvolupats, que consisteixen en l'ús de classificadors basats en SVM que operen dins
d'una finestra lliscant més un post-processament, van ser els únics presentats a les avaluacions
esmentades que no es basaven en models de Markov ocults (Hidden Markov Models) i cada un d'ells
va obtenir resultats competitius en la corresponent avaluació. La detecció d'activitat oral és un altre dels objectius d'aquest treball de tesi, pel fet de ser un cas particular de detecció d'events acústics especialment important. Es desenvolupa una tècnica de millora de l'entrenament dels SVM per fer front a la necessitat de reducció de l'enorme conjunt de dades existents. El sistema resultant, basat en SVM, és testejat amb uns quants conjunts de dades de l'avaluació NIST RT (Rich Transcription), on mostra puntuacions millors que les del sistema basat en GMM, malgrat que aquest darrer va quedar entre els primers en l'avaluació NIST RT de 2006.
Per acabar, val la pena esmentar alguns resultats col·laterals d'aquest treball de tesi. Com que s'ha dut a terme en l'entorn del projecte europeu CHIL, l'autor ha estat responsable de l'organització de les avaluacions internacionals de classificació i detecció d'events acústics abans esmentades, liderant l'especificació de les classes d'events, les bases de dades, els protocols d'avaluació i, especialment, proposant i implementant les diverses mètriques utilitzades. A més a més, els sistemes de detecció
s'han implementat en la sala intel·ligent de la UPC, on funcionen en temps real a efectes de test i demostració.
The human activity that takes place in meeting-rooms or class-rooms is reflected in a rich variety of acoustic events, either produced by the human body or by objects handled by humans, so the determination of both the identity of sounds and their position in time may help to detect and describe that human activity.
Additionally, detection of sounds other than speech may be useful to enhance the robustness of speech technologies like automatic speech recognition. Automatic detection and classification of acoustic events is the objective of this thesis work. It aims at processing the acoustic signals collected by distant microphones in meeting-room or classroom environments to convert them into symbolic descriptions corresponding to a listener's perception of the different sound events that are present in the signals and their sources. First of all, the task of acoustic event classification is faced using Support Vector Machine (SVM) classifiers, which are motivated by the scarcity of training data. A confusion-matrix-based variable-feature-set clustering scheme is developed for the multiclass recognition problem, and tested on the gathered database. With it, a higher classification rate than the GMM-based technique is obtained, arriving to a large relative average error reduction with respect to the best result from the conventional binary tree scheme. Moreover, several ways to extend SVMs to sequence processing are compared, in an attempt to avoid the drawback of SVMs when dealing with audio data, i.e. their restriction to work with fixed-length vectors, observing that the dynamic time warping kernels work well for sounds that show a temporal structure. Furthermore, concepts and tools from the fuzzy theory are used to investigate, first, the importance of and degree of interaction among features, and second, ways to fuse the outputs of several classification systems. The developed AEC systems are tested also by participating in several international evaluations from 2004 to 2006, and the results
are reported. The second main contribution of this thesis work is the development of systems for detection of acoustic events. The detection problem is more complex since it includes both classification and determination of the time intervals where the sound takes place. Two system versions are developed and tested on the datasets of the two CLEAR international evaluation campaigns in 2006 and 2007. Two kinds of databases are used: two databases of isolated acoustic events, and a database of interactive seminars containing a significant number of acoustic events of interest. Our developed systems, which consist of SVM-based classification within a sliding window plus post-processing, were the only submissions not using HMMs, and each of them obtained competitive results in the corresponding evaluation. Speech activity detection was also pursued in this thesis since, in fact, it is a -especially important - particular case of acoustic event detection. An enhanced SVM training approach for the speech activity detection task is developed, mainly to cope with the problem of dataset reduction. The resulting SVM-based system is tested with several NIST Rich Transcription (RT) evaluation datasets, and it shows better scores than our GMM-based system, which ranked among the best systems in the RT06 evaluation. Finally, it is worth mentioning a few side outcomes from this thesis work. As it has been carried out in the framework of the CHIL EU project, the author has been responsible for the organization of the above mentioned international evaluations in acoustic event classification and detection, taking a leading role in the specification of acoustic event classes, databases, and evaluation protocols, and, especially, in the proposal and implementation of the various metrics that have been used. Moreover, the detection systems have been implemented in the UPC's smart-room and work in real time for purposes of testing and demonstration.

Thesis (M.S.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 7, 2008) Includes bibliographical references.

The main objective of this research is the design and development of two different underwater acoustic emitters aimed to the deep-sea KM3NeT neutrino telescope, more specifically for the Acoustic Positioning System (APS) and for the calibration of the acoustic neutrino detection technique. The KM3NeT project is a new optical-based deep-sea neutrino telescope, currently under construction. The main objectives of the KM3NeT telescope are the discovery and observation of high-energy neutrino sources in the Universe and the determination of the mass hierarchy of neutrinos. The KM3NeT detectors consist of three-dimensional arrays of light sensor modules distributed over large volumes of the transparent water in the deep Mediterranean Sea. The sensor modules register the time of arrival of the light and the brightness of the light to reconstruct the direction and energy of the neutrino. In order to achieve an accurate deployment of the mechanical structures and a precise reconstruction of neutrino induced events, the telescope includes an APS as mandatory sub-system that provides an accurate position of the mechanical structures in real time. Additionally, the APS could also be an excellent tool to study the feasibility of an acoustic neutrino detector and a possible correlation between acoustic and optical signals. The new detector KM3NeT is an excellent opportunity to continue with the study of the acoustic neutrino detection. The acoustic detection would allow the combination of the two neutrino detection techniques for a hybrid underwater neutrino telescope, especially considering that the optical based telescope needs acoustic sensors to monitor the position of the sensors. An Acoustic Beacon (AB) as part of the APS of KM3NeT has been developed in this thesis. Previously, the first emitter prototype was developed and it was installed in previous neutrino telescopes, such as ANTARES and NEMO, in order to be tested in situ. The analyses of the in situ test with the prototypes were performed as part of this thesis. The results obtained from the tests showed that the requirements for the positioning system are accomplished, just needing few improvements for the final version. The final version of the AB is composed by a piezo-ceramic transducer and an electronic board integrated in a single piece in a cylindrical hard-anodized aluminium vessel. The design and the work done for a precise laboratory test was performed achieving optimal results in all aspects As second main work performed in this thesis, a parametric transducer array able to mimic the acoustic signal generated by Ultra-High Energy (UHE) neutrino interaction in water was designed and developed. The first part was designing a single transducer able to emit parametrically the acoustic neutrino signal. Afterwards, the design of the complete array system composed of few units was performed in order to achieve a more energetic and directional bipolar pulse.
El objetivo principal de esta investigación es el diseño y desarrollo de dos tipos de emisores acústicos diferentes para ser utilizados en el telescopio submarino de neutrinos KM3NeT, en concreto, uno como emisor en el sistema de posicionamiento acústico (APS) y otro para la calibración de la detección acústica de neutrinos. El proyecto KM3NeT es un telescopio óptico de neutrinos, que actualmente está en fase de construcción, y está ubicado en las profundidades del mar. Los objetivos principales del telescopio son el descubrimiento y la observación de las fuentes que originan los neutrinos de alta energía en el universo y la determinación de la jerarquía de masas de los neutrinos. Los detectores de KM3NeT consisten en conjuntos tridimensionales de módulos de sensores de luz distribuidos en grandes volúmenes de agua en las profundidades del mar Mediterráneo. Los módulos de sensores ópticos registran el tiempo de llegada de la luz y el brillo de la luz para reconstruir la dirección y la energía del neutrino. Con objeto de lograr una implementación correcta de las estructuras mecánicas y una reconstrucción precisa de los eventos del neutrino, el telescopio incluye el APS como subsistema necesario para proporcionar la posición exacta de las estructuras mecánicas en tiempo real. Además, el APS puede ser una herramienta excelente para estudiar la viabilidad de un detector de neutrinos acústico y de una posible correlación entre la señal acústica y óptica. El nuevo detector KM3NeT es una oportunidad para continuar con el estudio de detección acústica de neutrinos. La detección acústica permitiría la combinación de las dos técnicas de detección de neutrinos para un telescopio submarino de neutrinos híbrido, y más aún, teniendo en cuenta que el telescopio óptico necesita de sensores acústicos para monitorizar la posición de los sensores. En esta tesis, por un lado, se ha desarrollado un emisor acústico (AB) como parte del APS de KM3NeT. Previamente, se desarrolló el primer prototipo del emisor acústico, el cual se instaló en anteriores telescopios de neutrinos, concretamente en ANTARES y NEMO, con el fin de comprobar su funcionamiento in situ. Como parte de la tesis, se realizaron los análisis de las pruebas in situ y los resultados obtenidos mostraron que cumplía los requisitos del sistema de posicionamiento, únicamente se necesitaron algunas mejoras para la versión final. La versión final del AB está compuesta por un transductor piezo-cerámico y una placa electrónica integrado en una sola pieza en un recipiente cilíndrico de aluminio anodizado. El diseño y el trabajo realizado para una calibración precisa de laboratorio se llevó a cabo, logrando resultados óptimos en todos los aspectos requeridos. El segundo trabajo principal desarrollado en esta tesis consistió en el diseño de un array paramétrico de transductores capaz de imitar la señal acústica generada por la interacción del neutrino de ultra-alta energía (UHE) en el agua. La primera parte de su diseño se centró en el desarrollo de un transductor individual capaz de emitir paramétricamente la señal acústica del neutrino. Posteriormente, se realizó el diseño del array completo compuesto por varias unidades del transductor diseñado, con el objeto de lograr un pulso bipolar más enérgico y directivo.
L'objectiu principal d'esta investigació és el disseny i desenvolupament de dos tipus d'emissors acústics diferents per a ser utilitzats en el telescopi submarí de neutrins KM3NET, en concret, ú com emissor en el sistema de posicionament acústic (APS) i altre per a la calibració de la detecció acústica de neutrins. El projecte KM3NET és un telescopi òptic de neutrins, que actualment està en fase de construcció, i està ubicat en les profunditats del mar. Els objectius principals del telescopi són el descobriment i l'observació de les fonts que originen els neutrins d'alta energia en l'univers i la determinació de la jerarquia de masses dels neutrins. Els detectors de KM3NET consisteixen en conjunts tridimensionals de mòduls de sensors de llum distribuïts en gran volums d'aigua en el Mediterrani. Els mòduls de sensors òptics registren el temps d'aplegada de la llum i la intensitat de la llum per a reconstruir la direcció i l'energia del neutrí. Com objectiu d'aconseguir una implementació correcta de les estructures mecàniques i una reconstrucció precisa dels events del neutrí, el telescopi inclou l'APS com subsistema necessari per a proporcionar la posició exacta de les estructures mecàniques en temps real. A mes, l'APS pot ser una ferramenta excel¿lent per a estudiar la viabilitat d'un detector de neutrins acústic i d'una possible correlació entre el senyal acústic i òptic. El nou detector KM3NET és una oportunitat per a continuar en l'estudi de detecció acústica del neutrí. La detecció acústica permetria la combinació de les dos tècniques de detecció de neutrins per a un telescopi submarí de neutrins híbrid, i més encara, tenint en compte que el telescopi òptic necessita de sensors acústics per a monitoritzar la posició dels sensors. En aquesta tesis, per un costat, s'ha dissenyat un emissor acústic (AB) com part de l'APS de KM3NET. Prèviament, se desenvolupà el primer prototip de l'emissor acústic, el qual s'instal¿là en anteriors telescopis de neutrins, concretament en ANTARES i NEMO, amb el fi de comprovar-se el seu funcionament in situ. Com part de la tesis, es realitzaren els anàlisis de les proves in situ i els resultats obtinguts mostraren que complia els requisits del sistema de posicionament, únicament necessitant-se d'algunes millores per a la versió final. La versió final de l'AB està composta per un transductor piezo-ceràmic i una placa electrònica integrats en una sola peça en un recipient cilíndric d'alumini anoditzat. El disseny i el treball realitzat per a una calibració precisa de laboratori es va dur a terme, aconseguint resultats òptims en tots els aspectes requerits. Com segon treball principal desenvolupat en esta tesis, s'ha dissenyat un array paramètric de transductors capaç d'imitar el senyal acústic generat per l'interacció del neutrí d'ultra-alta energia (UHE) en l'aigua. La primera part de disseny es centrà en el desenvolupament d'un transductor individual capaç d'emetre paramètricament el senyal acústic del neutrí. Posteriorment, es va realitzar el disseny de l'array complet compost per varies unitats del transductor dissenyat, amb l'objectiu d'aconseguir un pols bipolar més energètic i directiu.
Saldaña Coscollar, M. (2017). Acoustic System Development for Neutrino Underwater Detectors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85981
TESIS

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009.
Thesis Advisor(s): Rice, Joseph A. ; Colosi, John A. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: Acoustic modem, Deep water, Transmission loss, Munk, Reliable Acoustic Path, RAP, Deep Sound Channel, DSC, Seaweb, Acoustic Communications, Acomms. Includes bibliographical references (p. 55-56). Also available in print.

This project was worked on during the autumn 2005 at the Norwegian University of Science and Technology, Department of Electronics and Telecommunications. The assignment was to write a new LabVIEW programme that is to run the measurement procedure of a laser probe setup. The setup is used in characterization of surface acoustic waves(SAW). A programme was written that contained the necessary functionality and proved to operate satisfactorily. Several measurements were made on a SAW transducer, accurately picturing the wave. Fourier analysis were performed on the collected data in order to separate the propagation directions. An absolute amplitude measurement was made on a heterodyne interferometer, and the result was compared to a similar scan made using the laser probe. The work shows that the setup is ready for calibration against the heterodyne interferometer, in order to enable the laser probe to measure absolute amplitude by itself.

This thesis considers the application of changepoint detection methodology for the analysis of acoustic sensing signals. In the first part, we propose a detection procedure for changes in the second-order structure of a univariate time series. This utilises a penalised likelihood based on Whittle’s approximation and allows for a non-linear penalty function. This procedure is subsequently used to detect changes in acoustic sensing data which correspond to external disturbances of the measuring cable. The second part shifts focus to multivariate time series, and considers the detection of changes which occur in only a subset of the variables. We introduce the concept of changepoint vectors which we use to model such changes. A dynamic programming scheme is proposed which obtains the optimal configuration of changepoint vectors for a given multivariate series. Consideration of pruning techniques suggests that these are not practically viable for this setting. We therefore introduce approximations which vastly improve computational speed with negligible detrimental impact on accuracy. This approximated procedure is applied to multivariate acoustic sensing data.

Ce travail se situe dans le contexte de l’utilisation des ondes de spin comme vecteur d’information. Il explore la possibilité d’exciter l’aimantation dans de fines couches ferromagnétiques grâce au couplage magnéto-élastique. Cela permettrait un adressage non-inductif, efficace, et distant des ondes de spin. Dans un premier volet, nous avons développé un dispositif expérimental générant des ondes acoustiques de surface (ODS) électriquement, verrouillées en phase à des impulsions de laser sonde. La dynamique d’aimantation est détectée grâce aux effets magnéto-optiques (Kerr et Voigt). Nous étudions le couplage magnétoélastique résonant dans une couche mince du semiconducteur magnétique (Ga,Mn)As. Afin d’atteindre la résonance, la fréquence des ondes de spin est ajustée à celle des ODS par un champ magnétique. Nous isolons les contributions photo-élastique et magnéto-optique du signal, pour quantifier l’amplitude de la précession d’aimantation. Nous montrons que la précession observée est exclusivement déclenchée par l’ODS. La variation en champ de son amplitude correspond très bien à celle calculée, et elle est maximum au champ pour laquelle l’absorption de l’ODS est maximale, démontrant clairement la résonance magnétoacoustique. L’influence de la fréquence et de la puissance de l’ODS, ainsi que de la température sur l’efficacité du couplage est également explorée. Dans un deuxième volet, nous avons excité des ODS par effet thermoélastique grâce à un faisceau laser focalisé, et cela sur des couches magnétiques métalliques cette fois-ci (Ni, FeGa, Co), déposées sur un substrat transparent (verre, sapphire). Des cartes spatio-temporelles du déplacement de la surface et du signal magnéto-optique ont été obtenues. Un décalage du spectre magnéto-optique vers les hautes fréquences semble indiquer une excitation des ondes de spin par les ODS
In the developing field of spin wave-based information technology, this work investigates the possibility to use surface acoustic waves (SAW) to excite spin-waves in ferromagnetic thin layers relying on the magnetoelastic coupling. This would provide a non-inductive, efficient, and remote addressing of spin waves. In the first project we develop an experimental setup to generate electrically excited SAWs phase-locked to probe laser pulses. The magnetization dynamics is detected by an optical bridge using magneto-optical effects (Kerr and Voigt). We investigate the resonant magneto-elastic coupling in a thin film of the ferromagnetic semiconductor (Ga,Mn)As. To reach resonant coupling, the spin-wave frequency is scanned across the SAW frequency using a magnetic field. We disentangle the photoelastic contribution from the magneto-optical one, from which we obtain the amplitude of magnetization precession. We show that it is driven solely by the acoustic wave. Its field dependence is shown to agree well with theoretical calculations. Its amplitude resonates at the same field as the resonant attenuation of the acoustic wave, clearly evidencing the magnetoacoustic resonance with high sensitivity. The influence of temperature, SAW frequency and power on the coupling efficiency are studied. In the second project we use SAWs thermoelastically excited by a tightly focused laser beam on ferromagnetic metals (Ni, FeGa, Co) on a transparent substrate (glass, sapphire). Spatio-temporal maps of the surface displacement and magneto-optical signal are obtained. A high-frequency shift of the frequency spectrum of the latter gives a hint for spin-wave excitation by SAWs

Aerosol particle detection and determination finds important applications in the commercial, military and aerospace sectors. Monitoring of clean room environments, and spacecraft integration and check out facilities are some of the most important aplications. In the early days test filters were examined with a microscope to determine the number and size of particles that were being removed from air. Today, most of the commercially available clean room airborne particle counters work on a light scattering principle. They are referred to as Optical Particle Counter or OPC. Essentially, they utilize a very bright laser light source to illuminate the particles. The burst of light energy is converted into a pulse of electrical energy. By measuring the height of the signal and counting the number of pulses the sizes and quantities of particles could thus be determined. The microscope and the OPC techniques have their limitations. The microscope technique is a post contamination assessment technique and the OPC is costly, hard to maintain, lack in counting efficiency and is not mobile. This experimental study demonstrates a novel and inexpensive particle detection technique which is based on the acoustic signature of airborne particles as they are accelerated through an acoustic transducer. The transducer consists of an inlet converging nozzle, a capillary tube and an expansion section. If the air is laden with particles, as the flow accelerates through the inlet, the particles cannot follow the large change in velocity due to their inertia. Vortices are generated as air flows over the particles prior to entering the capillary. These vortices are believed to generate sound, which is amplified by the transducer acting as an organ pipe. This sound emission if measured contains frequencies that are harmonics of the natural frequency of the transducer's air column. Results show how the frequency content of the acoustic signature relates to the fundamental frequency of the transducer's air column. The transducer is able to detect micron sized particles ( 5 to 50 micron) and the sound intensity is a function of the flowrate but not of particle size. This study also shows the ability of the transducer to determine particle concentration as low as few parts per liter (ppl) and compare the data with that obtained from a commercially available aerodynamic particle sizer.
M.S.M.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering

The detection of the Acoustic Events (AEs) naturally produced in a meeting room may help to describe the human and social activity. The automatic description of interactions between humans and environment can be useful for providing: implicit assistance to the people inside the room, context-aware and content-aware information requiring a minimum of human attention or interruptions, support for high-level analysis of the underlying acoustic scene, etc. On the other hand, the recent fast growth of available audio or audiovisual content strongly demands tools for analyzing, indexing, searching and retrieving the available documents. Given an audio document, the first processing step usually is audio segmentation (AS), i.e. the partitioning of the input audio stream into acoustically homogeneous regions which are labelled according to a predefined broad set of classes like speech, music, noise, etc. Acoustic event detection (AED) is the objective of this thesis work. A variety of features coming not only from audio but also from the video modality is proposed to deal with that detection problem in meeting-room and broadcast news domains. Two basic detection approaches are investigated in this work: a joint segmentation and classification using Hidden Markov Models (HMMs) with Gaussian Mixture Densities (GMMs), and a detection-by-classification approach using discriminative Support Vector Machines (SVMs). For the first case, a fast one-pass-training feature selection algorithm is developed in this thesis to select, for each AE class, the subset of multimodal features that shows the best detection rate. AED in meeting-room environments aims at processing the signals collected by distant microphones and video cameras in order to obtain the temporal sequence of (possibly overlapped) AEs that have been produced in the room. When applied to interactive seminars with a certain degree of spontaneity, the detection of acoustic events from only the audio modality alone shows a large amount of errors, which is mostly due to the temporal overlaps of sounds. This thesis includes several novelties regarding the task of multimodal AED. Firstly, the use of video features. Since in the video modality the acoustic sources do not overlap (except for occlusions), the proposed features improve AED in such rather spontaneous scenario recordings. Secondly, the inclusion of acoustic localization features, which, in combination with the usual spectro-temporal audio features, yield a further improvement in recognition rate. Thirdly, the comparison of feature-level and decision-level fusion strategies for the combination of audio and video modalities. In the later case, the system output scores are combined using two statistical approaches: weighted arithmetical mean and fuzzy integral. On the other hand, due to the scarcity of annotated multimodal data, and, in particular, of data with temporal sound overlaps, a new multimodal database with a rich variety of meeting-room AEs has been recorded and manually annotated, and it has been made publicly available for research purposes.
La detecció d'esdeveniments acústics (Acoustic Events -AEs-) que es produeixen naturalment en una sala de reunions pot ajudar a descriure l'activitat humana i social. La descripció automàtica de les interaccions entre els éssers humans i l'entorn pot ser útil per a proporcionar: ajuda implícita a la gent dins de la sala, informació sensible al context i al contingut sense requerir gaire atenció humana ni interrupcions, suport per a l'anàlisi d'alt nivell de l'escena acústica, etc. La detecció i la descripció d'activitat és una funcionalitat clau de les interfícies perceptives que treballen en entorns de comunicació humana com sales de reunions. D'altra banda, el recent creixement ràpid del contingut audiovisual disponible requereix l'existència d'eines per a l'anàlisi, indexació, cerca i recuperació dels documents existents. Donat un document d'àudio, el primer pas de processament acostuma a ser la seva segmentació (Audio Segmentation (AS)), és a dir, la partició de la seqüència d'entrada d'àudio en regions acústiques homogènies que s'etiqueten d'acord amb un conjunt predefinit de classes com parla, música, soroll, etc. De fet, l'AS pot ser vist com un cas particular de la detecció d’esdeveniments acústics, i així es fa en aquesta tesi. La detecció d’esdeveniments acústics (Acoustic Event Detection (AED)) és un dels objectius d'aquesta tesi. Es proposa tot una varietat de característiques que provenen no només de l'àudio, sinó també de la modalitat de vídeo, per fer front al problema de la detecció en dominis de sala de reunions i de difusió de notícies. En aquest treball s'investiguen dos enfocaments bàsics de detecció: 1) la realització conjunta de segmentació i classificació utilitzant models de Markov ocults (Hidden Markov Models (HMMs)) amb models de barreges de gaussianes (Gaussian Mixture Models (GMMs)), i 2) la detecció per classificació utilitzant màquines de vectors suport (Support Vector Machines (SVM)) discriminatives. Per al primer cas, en aquesta tesi es desenvolupa un algorisme de selecció de característiques ràpid d'un sol pas per tal de seleccionar, per a cada AE, el subconjunt de característiques multimodals que aconsegueix la millor taxa de detecció. L'AED en entorns de sales de reunió té com a objectiu processar els senyals recollits per micròfons distants i càmeres de vídeo per tal d'obtenir la seqüència temporal dels (possiblement superposats) esdeveniments acústics que s'han produït a la sala. Quan s'aplica als seminaris interactius amb un cert grau d'espontaneïtat, la detecció d'esdeveniments acústics a partir de només la modalitat d'àudio mostra una gran quantitat d'errors, que és sobretot a causa de la superposició temporal dels sons. Aquesta tesi inclou diverses contribucions pel que fa a la tasca d'AED multimodal. En primer lloc, l'ús de característiques de vídeo. Ja que en la modalitat de vídeo les fonts acústiques no se superposen (exceptuant les oclusions), les característiques proposades Resum iv milloren la detecció en els enregistraments en escenaris de caire espontani. En segon lloc, la inclusió de característiques de localització acústica, que, en combinació amb les característiques habituals d'àudio espectrotemporals, signifiquen nova millora en la taxa de reconeixement. En tercer lloc, la comparació d'estratègies de fusió a nivell de característiques i a nivell de decisions, per a la utilització combinada de les modalitats d'àudio i vídeo. En el darrer cas, les puntuacions de sortida del sistema es combinen fent ús de dos mètodes estadístics: la mitjana aritmètica ponderada i la integral difusa. D'altra banda, a causa de l'escassetat de dades multimodals anotades, i, en particular, de dades amb superposició temporal de sons, s'ha gravat i anotat manualment una nova base de dades multimodal amb una rica varietat d'AEs de sala de reunions, i s'ha posat a disposició pública per a finalitats d'investigació. Per a la segmentació d'àudio en el domini de difusió de notícies, es proposa una arquitectura jeràrquica de sistema, que agrupa apropiadament un conjunt de detectors, cada un dels quals correspon a una de les classes acústiques d'interès. S'han desenvolupat dos sistemes diferents de SA per a dues bases de dades de difusió de notícies: la primera correspon a gravacions d'àudio del programa de debat Àgora del canal de televisió català TV3, i el segon inclou diversos segments d'àudio del canal de televisió català 3/24 de difusió de notícies. La sortida del primer sistema es va utilitzar com a primera etapa dels sistemes de traducció automàtica i de subtitulat del projecte Tecnoparla, un projecte finançat pel govern de la Generalitat en el que es desenvoluparen diverses tecnologies de la parla per extreure tota la informació possible del senyal d'àudio. El segon sistema d'AS, que és un sistema de detecció jeràrquica basat en HMM-GMM amb selecció de característiques, ha obtingut resultats competitius en l'avaluació de segmentació d'àudio Albayzín2010. Per acabar, val la pena esmentar alguns resultats col·laterals d’aquesta tesi. L’autor ha sigut responsable de l'organització de l'avaluació de sistemes de segmentació d'àudio dins de la campanya Albayzín-2010 abans esmentada. S'han especificat les classes d’esdeveniments, les bases de dades, la mètrica i els protocols d'avaluació utilitzats, i s'ha realitzat una anàlisi posterior dels sistemes i els resultats presentats pels vuit grups de recerca participants, provinents d'universitats espanyoles i portugueses. A més a més, s'ha implementat en la sala multimodal de la UPC un sistema de detecció d'esdeveniments acústics per a dues fonts simultànies, basat en HMM-GMM, i funcionant en temps real, per finalitats de test i demostració.

Artificial insemination (AI) is a widely used part of the modern agricultural industry, with the number of animals inseminated globally being measured in the millions per anum. Crucial to the success of AI is that the sperm sample used is of a high Quality. Two factors which determine the quality of the sample are the number of sperm present and their motility. There are numerous methods used to analyse the quality of a sperm sample, but these are generally laboratory based, expensive and in need of a skilled operator to perform the analysis. It would, therefore be useful to have a simple and inexpensive system which could be used outside the laboratory, immediately prior to the insemination of the animal. Presented in this thesis is work developing a time of flight (ToF) technique which makes use of a quartz crystal microbalance (QCM), operating at 5 MHz, as the sensing element. Data is shown developing a device where a 50 μl sample of boar sperm is added to a liquid filled swim channel, which the sperm are allowed to self-propel down and attach to the surface of a QCM at the end. The attachment of the sperm to the surface causes a measurable frequency decrease in the QCM, aproximately 50 Hz. An average effective mass measurement was made using a QCM and gave a value of 8 ± 5 pg per sperm, which was used in conjunction with the frequency change to determine the number rate of sperm reaching the QCM. Additional data is presented to investigate the effect of environmental temperature on the ToF of the sperm, showing a decrease in ToF between 23 0C to 37 0C. The system was also used to investigate increasing the swim speed of the sperm by chemical means. A range of 20 μmol to 100 μmol of progesterone was added to the swim medium and the ToF was shown to decrease as a result. To further develop the system, large commercial electronics were replaced by smaller circuits built in-house. An oscillator circuit based on a Pierce oscillator was used to drive the QCM and a frequency counter circuit making use of a universal frequency to digital converter (UFDC-1) was used to measure the frequency of the QCM. ToF experiments were performed which showed these pieces of equipment to be effective for performing the analysis of sperm samples. The swim cell itself was also refined, resulting in a compact, modular design. Work was performed developing layer-guided, single-port acoustic resonators to replace the QCM as the sensing element in the sperm analysis device. A maximum mass sensitivity of 1110 Hzμg-1cm-2 was found for devices on a LiTaO3 substrate with a 6 μm guiding layer. While viscosity-density sensing experiments found a maximum sensitivity of 488 KHz Pa-1/2 kg1/2 for a 4 μm guiding layer.

Existing weapon detection systems such as metal detectors and X-ray baggage scanners have many drawbacks. While metal detectors can only detect metallic objects, X-ray scanners are unsafe for use on passengers. Also, these systems can only scan people within a short range. These limitations of detecting potentially harmful objects have led to tragic events such as the 9/11 attack on the world trade centre and the 2008 terrorist attack in Mumbai. Development of more advanced security systems would help in curbing such terrorist attacks. These systems could also be used to help security officials in tackling knife and gun related crimes in the streets. The aim of this research is to develop a concealed weapon detection system using acoustic waves. Ideally, the system would have large standoff distance, should be cost-effective and easy to manufacture and would be able to detect both metal and non-metallic weapons. Different techniques such as acoustic signature, resonance acoustic spectroscopy and acoustic imaging were analysed. Acoustic signature techniques identify the target by comparing the acoustic waves reflected by the target to a database of previously recorded acoustic reflections. Resonance acoustic spectroscopy was used on the data acquired using both experimental measurements and Finite Element simulations. A series of resonant frequencies from the acoustic waves reflected by the concealed target were extracted using this technique. This series of resonant frequencies that are unique to the target were used to identify the target. Acoustic camera was used to experimentally record the acoustic reflection from different targets. This was then used to develop images of concealed targets. These tests were performed using commercially available array speaker systems. The probability of improving these results using a better designed ultrasonic or acoustic array speaker system was analysed. This was done by changing different array design parameters and obtaining a highly focused acoustic beam. The results from the experimental tests and Finite Element simulations proved the possibility of using acoustic waves for concealed weapon detection. In the acoustic signature measurements, the frequency spectra of the reflected acoustic waves were shown to be different for different targets. The results from resonance acoustic spectroscopy showed structural resonant frequencies in the frequency spectra that corresponded to the natural frequency of the target. Using acoustic camera kit the image of the concealed target was identified. The array results showed the formation of focused beams for different array configurations. The results showed the formation of grating lobes and side lobes when the inter-element gap became larger than the wavelength of sound waves at the excitation frequency. Finally, a program using neural network was developed to demonstrate how the natural frequencies from the target could be used to identify them. This research work provides a proof of concept of different acoustic wave-based detection and imaging techniques. It has shown the possibility of detecting concealed targets at standoff distances. Using parametric arrays highly focused acoustic or ultrasonic beams could be generated which could be focused on a person suspected of carrying a weapon in a crowded environment. The sound waves reflected back could be analysed using the resonance acoustic spectroscopic technique or one could use the acoustic camera to generate images of targets in real-time. The use of acoustic waves would also help in keeping the cost and complexity of the equipment to a minimum. It also ensures that the public is not exposed to any harmful radiation. The techniques described in this thesis would significantly support the development of a commercially viable, robust acoustic waves based concealed weapon detection system.

This thesis presents the development of a computer model for the simulation of the sidescan sonar process. The motivation for the development of this model is the creation of a unique and powerful visualisation tool to improve understanding and interpretation of the sidescan sonar process and the images created by it. Existing models tend to generate graphical or numerical results, but this model produces synthetic sidescan sonar images as the output. This permits the direct visualisation of the influence of individual parameters and features of the sonar process on the sidescan images. The model considers the main deterministic aspects of the underlying physical processes which result in the generation of sidescan sonar images. These include the propagation of the transmitted pulse of acoustic energy through the water column to its subsequent interaction and scattering from the rough seafloor. The directivity and motion characteristics of the sonar transducer are also incorporated. The thesis documents the development of the model to include each of these phenomena and their subsequent effect on the sidescan sonar images. Finally, techniques are presented for the investigation and verification of the synthetic sidescan images produced by the model.

Aperture synthesis, as its name implies, synthesises an aperture by storing successive echoes obtained from a moving platform and by processing the results as if they had been obtained from a multi-element array enables a high azimuth resolution to be obtained from a physically small array. The technique has been highly successful in radio astronomy, and in both satellite and aircraft borne radar. However the use of this technique has been very limited in the sonar environment mainly because of difficulties of maintaining a stable track under water and problems of under-sampling of the aperture arising from the relatively slow velocity of acoustic waves in water. The thesis describes a study of the application of the synthetic aperture technique to sonar, highlighting some of these difficulties and possible means of overcoming them. A study has also been made the application of the bathymetric technique, a technique for measuring the height of objects on the sea bed, to synthetic aperture sonar. In addition to the theoretical work and computer simulation, an experimental system has been built in a water tank measuring some 9m by 5m by 2m deep in order to test a number of the algorithms and some good results have been obtained.