The purpose of this work was to understand the influence of materials and construction on football performance. Two main areas identified as needing further work were post-impact rebound deviation and acoustic response. To further investigate these areas, football materials were tested in a lab with different loading scenarios and the resulting data was used in various characterisation methods to help define finite element models. The finite element models were used to efficiently explore a variety of material and construction variations. Acoustic data for a range of balls was collected in an anechoic chamber and advanced coupled Eulerian-Lagrangian simulations were developed to visualise the mode shapes of internal resonances.

This project includes an overview of different processing methods phonograms. It focuses primarily on time - frequency analysis carried out using Fast Fourier Transform (STFT). The main essence is to evaluate the time - frequency analysis of recorded motor vehicle, driving at different options, together with an analysis of driver activity in these variants. Based on the results of the analysis deals with the creation of synthetic audio signals of motor vehicle records. Further addresses the creation of the program for acoustic simulation engine is running smoothly when driving a car. Processing recorded signals and their evaluation is transferred using Matlab 7.7.0 ( R2008 )

Acoustic models are useful tools to increase understanding of cochlear implant perception. Two particular issues in modelling cochlear implant perception were considered in the present study, which aimed at improving acoustic models. The first included an electricallayer in the model, while the second manipulated synthesis signal parameters. Two parts of the study explored the effects of current decay, compression function and simultaneous stimulation, by including the electrical layer. The SPREAD model, which incorporated this layer, yielded the asymptote in speech intelligibility at seven channels observed in CI listeners. It was shown that the intensity of border channels was deemphasized in relation to more central channels. This was caused by the one-sided effects of current spread from neighbouring channels for the border channels, as opposed to the two-sided effects for the more central channels. It was theorised that more compressive mapping functions would affect spectral cues and consequently speech intelligibility, but speech intelligibility experiments did not confirm this theory. A simultaneous analogue stimulation (SAS) model, which modelled simultaneous stimulation, yielded intelligibility results that were lower than those of the SPREAD model at 16 channels. The SAS model also appeared to introduce more temporal distortion than the SPREAD model. A third part of the study endeavoured to improve correspondence of acoustic model results with cochlear implant listener results by using nine different synthesis signals. The best synthesis signal was noise-band based. The widths of these increased linearly from 0.4 mm at the apical to 8 mm at the basal end. Good correspondence between speech recognition outcomes using this synthesis signal with those of CI listeners was found. AFRIKAANS : Akoesties modelle word algemeen gebruik om die persepsie van inplantingsgebruikers beter te verstaan. Twee benaderings tot die modellering van kogleêre inplantingsgebruikerpersepsies is voorgestel om akoestiese modelle te verbeter. In die eerste benadering is die generiese model verbeter deur die byvoeging van 'n elektriese laag en in die tweede benadering is sinteseseinparameters gemanipuleer om die ooreenkoms met inplantingsgebruikersuitkomste te verbeter. Twee dele van die studie het die effek van stroomverspreiding, samedrukkings-funksie en gelyktydige stimulasie ondersoek deur die insluiting van die elektriese laag. Die SPREAD-model het die asimptoot in spraakherkenning by sewe kanale getoon. Die intensiteit van grenskanale is onderbeklemtoon in verhouding met meer sentrale kanale. Dit is veroorsaak deur die eensydige effekte van stroomverspreiding vir die grenskanale, teenoor die tweesydige effekte wat meer sentrale kanale tipies beïnvloed. Die model het gesuggereer dat meer samedrukkende funksies spektrale inligting sou affekteer, maar spraakherkenningsdata het nie hierdie teorie bevestig nie. Die gelyktydige- analoogstimulasiemodel, wat gelyktydige stimulasie gemodelleer het, het soortgelyke tendense getoon, maar met meer temporale effekte as die SPREAD-model. Die gelyktydige- analoogstimulasiemodel-model se resultate was ook swakker by 16 kanale as die SPREAD-modelresultate. Die derde deel van die studie het gepoog om beter ooreenkoms tussen modeluitkomste en inplantingsgebruikeruitkomste te verkry deur nege verskillende sinteseseine te gebruik. Die beste sintesesein was die ruisband met veranderende wydte; hierdie wydte het verbreed vanaf 0.4 mm by die apeks tot by 8 mm by die basis. 'n Goeie ooreenkoms is verkry tussen modeluitkomste en inplantingsgebruikeruitkomste deur hierdie sintesesein te gebruik. / Thesis (PhD)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / Unrestricted

An important facet of creating high-quality vehicles is to create components that are quiet and smooth under operation. In reality, however, it is challenging to measure the sound that some automotive components make under load because it requires specialist facilities and equipment which are expensive to acquire. Furthermore, the motors used in testbeds drown out the noise emitted from much quieter components, such as a Power Transfer Unit (PTU). This thesis aims to solve these issues by outlining the steps required to virtually estimate the acoustic radiation of a PTU using the Transmission Error (TE) as the input excitation via multi-body dynamics (MBD). MBD is used to estimate the housing vibrations, which can then be coupled with an acoustic tool to create a radiation analysis. Thus, creating a viable method to measure the acoustic performance without incurring significant expenses. Furthermore, it enables noise and vibration analyses to be incorporated more easily into the design stage. This thesis analysed the sound radiated due to gear whine which arises due to the TE and occurs at the gear mesh frequency and its multiples. The simulations highlighted that the TE can be accurately predicted using the methods outlined in this thesis. Similarly, the method can reliably obtain the vibrations of the housing. The results from this analysis show that at 2000 rpm the PTU was sensitive to vibrations at 500, 1000 and 1500 Hz, the largest amplitude being at 1000 Hz. Furthermore, the Sound Power Level (SWL) was proportional to the vibration amplitudes in the system. Analytical calculations were conducted to verify the methods and showed a strong correlation. However, it was concluded that experiments are required to further verify the findings in this thesis. / En viktig aspekt i att skapa fordon av hög kvalitet är att skapa komponenter som är tysta och smidiga under drift. I verkligheten är det dock svårt att mäta ljudet som vissa fordonskompo- nenter ger under belastning eftersom det kräver specialanläggningar och utrustning, vilket är dyrt att skaffa. Dessutom maskerar motorerna som används i testbäddar ut bullret från mycket tystare komponenter, till exempel en kraftöverföringsenhet (PTU). Detta examensar- bete syftar till att lösa dessa problem genom att beskriva de steg som krävs för att virtuellt uppskatta den akustiska strålningen av en PTU med hjälp av transmissionsfelet (TE) som ingångsexcitation via flerkroppsdynamik (multi-body dynamics, MBD). MBD används för att uppskatta kåpans vibrationer, som sedan kan kopplas till ett akustiskt verktyg för att skapa en ljudutstrålningsanalys. Således skapas en genomförbar metod för att mäta den akustiska pre- standan utan att medföra betydande kostnader. Dessutom möjliggör det att lättare integrera ljud- och vibrationsanalyser i designfasen. Detta examensarbete analyserade ljudet som utstrålats på grund av kugghjulsljud, som uppstår på grund av TE och uppträder vid kuggingreppsfrekvensen och dess multiplar. Simuleringarna belyste att TE kan förutsägas exakt med de metoder som beskrivs i detta examensarbete. På samma sätt kan metoden på ett tillförlitligt sätt uppnå kåpans vibrationer. Resultaten från denna analys visar att vid 2000 rpm var PTU känslig för vibrationer vid 500, 1000 och 1500 Hz, den största amplituden var vid 1000 Hz. Dessutom var ljudeffektsnivån (SWL) proportionell mot vibrationsamplituderna i systemet. Analytiska beräkningar genomfördes för att verifiera metoderna och visade en stark korrelation. Dock drogs slutsatsen att experiment krävs för att ytterligare verifiera resultaten i detta arbete.

Networked, multi-sensor array systems have proven to be advantageous in the sensor world. A large amount of research has been conducted with these systems, with a main interest in data fusion. Intelligently processing the large amounts of data collected by these systems is required in order to fully utilize the benefits of a multi-sensor array system. A robust but flexible simulation environment would provide a platform for accurately comparing current and future data fusion theories. This thesis proposes a simulator model for testing fusion theories for these acoustic multi-sensor networks. An iterative, lossless data fusion algorithm was presented as the model for simulation development. The arrangement and orientation of objects in the simulation environment, as well as most other system parameters are defined by the user before the simulation runs. The sensor data, including noise, is generated at the appropriate time delay and propagation loss before being processed by a delay and sum beamformer and a matched filter. The resulting range-Doppler maps are modified to probability density functions, and translated to a single point of reference. The data is then combined into a single world model. An iterative process is used to filter out false targets and amplify true target detections. Data is fused from each multi-sensor array and from each simulation run. Target amplitudes are gained if they are present in all combined world models, and are otherwise reduced. This thesis presents the results of the fusion algorithm used, including multiple iterations, to prove the algorithms effectiveness. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The study of room acoustics is linked to the importance of sound inside a room, so the architectural characteristics of the internal space determine the acoustic behavior. To get better acoustics of a room there are computational methods that simulate the acoustic behavior of a room before his execution, providing the prediction of the simulated environment behavior from the acoustic point of view. The acoustic parameters of the resulting acoustic simulations as Reverberation Time, Initial Decay Time, Clarity, Sharpness and Speech Transmission Index, are responsible for identifying the acoustic conditions of the geometric model of a classroom. This geometric model used as sample classrooms of different types of municipal schools in Santa Maria - RS, with the aim of developing a classroom typology for the music teaching from virtual acoustic models using computing simulation. Geometric models of classrooms for teaching music were developed using as input data, dimensions, shapes and elements usually used in these environments and developed representative virtual acoustic models these virtual classrooms, in which were measured acoustic parameters related to the reverberation time from the impulse response of the acoustic models of virtual rooms. We analyzed the experimental results and simulated with and without furniture for the acoustic parameters, and these comparisons were related to the values of JND (Just Noticeable Difference) near the standard tolerance according to ISO 3382/2009 with normalized values of 500 Hz to 1000 Hz. A geometric study was developed based on Bolt (1946) which defined the appropriate geometric measures of the room. Thus, a functional typology was originated which meets the architectural acoustic requirements and the initial proposal of presenting a music classroom typology providing an environment with acoustic quality, according to Law number 11.769/2008 that inserts education music in schools on a mandatory basis. / O estudo da acústica de salas está vinculado à importância do som dentro de um recinto, logo, as características arquitetônicas do espaço interno determinam seu comportamento acústico. Para buscar melhores condições acústicas de um recinto disponibilizam-se métodos computacionais que simulem o comportamento acústico de uma sala, antes de sua execução, proporcionando a previsão de comportamento do ambiente simulado do ponto de vista acústico. Os parâmetros acústicos resultantes das simulações acústicas, como: Tempo de Reverberação, Tempo de Decaimento Inicial, Clareza, Definição e o Índice de Transmissão da Fala são responsáveis pela identificação das condições acústicas do modelo geométrico de uma sala de aula. Este modelo geométrico utilizou como amostra as salas de aula das diferentes tipologias de escolas da rede estadual de educação de Santa Maria - RS, com o objetivo de desenvolver uma tipologia de sala de aula, para o ensino da música, a partir de modelos acústicos virtuais utilizando-se simulação computacional. Foram desenvolvidos modelos geométricos de salas de aula para o ensino da música utilizando-se como dados de entrada, dimensões, formatos e elementos, usualmente utilizados nestes ambientes, e desenvolvidos modelos acústicos virtuais representativos destas salas, aos quais foi feita uma avaliação dos parâmetros acústicos relacionados ao tempo de reverberação, partindo-se da resposta impulso dos modelos acústicos virtuais das salas. Foram analisados resultados experimentais e simulados na situação sem mobília e com mobília, para os parâmetros acústicos, e essas comparações foram relacionadas com os valores de JND (em inglês Just Noticeable Difference) padronizadas as margens de tolerância, de acordo com a ISO 3382/2009, com valores normalizados de 500 Hz a 1000 Hz. Também foi desenvolvido um estudo geométrico, a partir de Bolt (1946), que definiu as medidas geométricas adequadas da sala. Com isto, originou-se uma tipologia funcional, observando as exigências acústicas arquitetônicas, cumprindo a proposta inicial de apresentar uma tipologia de sala de aula, para a música, a fim de proporcionar um ambiente com qualidade acústica, atendendo a Lei nº 11.769/2008, que insere o ensino da música nas escolas, de forma obrigatória.

Disscusion of influencis of shape and dimension of human ear-canal in gain characteristic inclucing pressure wave applied on tympanic membrane in earphone implementation.

Two separate methods are presented to aid in the creation and evaluation of acoustic simulations. The first is a hybrid method that allows separate low and high-frequency acoustic responses to be combined into a single broadband response suitable for auralization. The process consists of four steps: 1) creating separate low-frequency and high-frequency responses of the system of interest, 2) interpolating between the two responses to get a single broadband magnitude response, 3) adding amplitude modulation to the high-frequency portion of the response, and 4) calculating approximate phase information. An experimental setup is used to validate the hybrid method. Listening tests are conducted to assess the realism of simulated auralizations compared to measurements. The listening tests confirm that the method is able to produce realistic auralizations, subject to a few limitations. The second method presented is a machine learning approach for predicting human perceptions of audio fidelity and sound quality. Several algorithms are compared and various audio features considered in developing the machine learning models. The developed models accurately predict human perceptions of audio fidelity and sound quality in three distinct applications: assessing the fidelity of compressed audio, evaluating the fidelity of simulated audio, and comparing the sound quality of loudspeakers. The high accuracies achieved confirm that machine learning models could potentially supplant listening tests, significantly decreasing the time required to assess audio quality or fidelity.

É cada vez maior a preocupação com a poluição sonora gerada pelos transformadores de potência de subestações elétricas. Atualmente, o controle desse tipo de ruído é feito utilizando-se métodos passivos, que são caros e dificultam a manutenção dos transformadores. Uma alternativa para os métodos passivos é o controle ativo de ruído (ANC). Apesar de extensas pesquisas realizadas nas últimas três décadas, ainda não existem soluções comercialmente viáveis para o ANC de transformadores. As dificuldades para a aplicação bem sucedida do ANC para transformadores foram investigadas por meio de simulações e de testes com protótipo. Os três maiores obstáculos identificados foram: o posicionamento dos transdutores eletroacústicos; a obtenção de atenuação em uma região longe do transformador, usando um número reduzido de fontes de controle e de sensores de erro, os últimos colocados ainda na região de campo acústico próximo; e a identificação robusta do caminho secundário com baixa razão sinal/ruído. Os dois primeiros problemas foram abordados, analisando-se algumas alternativas de soluções. Algoritmos genéticos (GA) foram utilizados para a otimização da posição dos transdutores do sistema ANC. O desempenho desses algoritmos depende fortemente da modelagem acústica realizada e verificou-se que o método de Usry, escolhido para modelar o campo primário do transformador, não forneceu estimativa adequada. Usando um modelo mais simples de fonte primária, constatou-se a importância da função de mérito para o desempenho do GA. Também foi verificado que a otimização conjunta das posições dos transdutores fornece o mesmo resultado, e em menor tempo, que a otimização das posições das fontes de controle e dos sensores de erro separadamente. Simulações realizadas com uma nova estratégia de sensores virtuais (baseada no janelamento das fontes de controle) mostra que é possível aumentar o nível de atenuação longe do transformador, mesmo com um número pequeno de fontes de controle e sensores de erro. Testes com um protótipo de sistema ANC foram feitos em laboratório e em campo e os resultados desses testes são discutidos detalhadamente. / Concern regarding noise pollution caused by power transformers in electrical substations is increasing. Nowadays, this kind of noise is controlled using passive methods, which are expensive and make transformer maintenance more difficult. An alternative to passive methods is active noise control (ANC). However, despite extensive research undertaken in the last three decades, there is still no viable commercial solution for the active control of transformer noise. The difficulties for a successful implementation of an ANC solution in the case of power transformer noise are investigated through simulations and tests with a prototype. The three main obstacles found were: the positioning of the electro-acoustic transducers; the achievement of sufficient attenuation in a region far from the transformer, using a small number of control sources and error sensors (when the latter are positioned on the region of acoustic near-field); and the robust identification of the secondary path in a low signal/noise situation. The two former problems were dealt with, and some alternative solutions were analyzed. Genetic algorithms (GA) were used for the optimization of the transducers\' position. The performance of these algorithms is strongly related to the acoustical model used and it was verified that the Usry method, used for modelling the transformers primary field, did not result in an adequate estimate. Using a simplified model for the primary source, the importance of the cost function in the GA\'s performance was made evident. It was also verified that the joint optimization of transducers\' position provides the same result, and in shorter time, as the independent optimization of control source and error sensor positions. Simulations with a new virtual sensor strategy (based on windowing the control sources) show that it is possible to increase attenuation levels in a region far from the transformer, even with a small number of control sources and error sensors. Laboratory and field tests with an ANC system prototype were undertaken and the results of these tests are thoroughly discussed.

É cada vez maior a preocupação com a poluição sonora gerada pelos transformadores de potência de subestações elétricas. Atualmente, o controle desse tipo de ruído é feito utilizando-se métodos passivos, que são caros e dificultam a manutenção dos transformadores. Uma alternativa para os métodos passivos é o controle ativo de ruído (ANC). Apesar de extensas pesquisas realizadas nas últimas três décadas, ainda não existem soluções comercialmente viáveis para o ANC de transformadores. As dificuldades para a aplicação bem sucedida do ANC para transformadores foram investigadas por meio de simulações e de testes com protótipo. Os três maiores obstáculos identificados foram: o posicionamento dos transdutores eletroacústicos; a obtenção de atenuação em uma região longe do transformador, usando um número reduzido de fontes de controle e de sensores de erro, os últimos colocados ainda na região de campo acústico próximo; e a identificação robusta do caminho secundário com baixa razão sinal/ruído. Os dois primeiros problemas foram abordados, analisando-se algumas alternativas de soluções. Algoritmos genéticos (GA) foram utilizados para a otimização da posição dos transdutores do sistema ANC. O desempenho desses algoritmos depende fortemente da modelagem acústica realizada e verificou-se que o método de Usry, escolhido para modelar o campo primário do transformador, não forneceu estimativa adequada. Usando um modelo mais simples de fonte primária, constatou-se a importância da função de mérito para o desempenho do GA. Também foi verificado que a otimização conjunta das posições dos transdutores fornece o mesmo resultado, e em menor tempo, que a otimização das posições das fontes de controle e dos sensores de erro separadamente. Simulações realizadas com uma nova estratégia de sensores virtuais (baseada no janelamento das fontes de controle) mostra que é possível aumentar o nível de atenuação longe do transformador, mesmo com um número pequeno de fontes de controle e sensores de erro. Testes com um protótipo de sistema ANC foram feitos em laboratório e em campo e os resultados desses testes são discutidos detalhadamente. / Concern regarding noise pollution caused by power transformers in electrical substations is increasing. Nowadays, this kind of noise is controlled using passive methods, which are expensive and make transformer maintenance more difficult. An alternative to passive methods is active noise control (ANC). However, despite extensive research undertaken in the last three decades, there is still no viable commercial solution for the active control of transformer noise. The difficulties for a successful implementation of an ANC solution in the case of power transformer noise are investigated through simulations and tests with a prototype. The three main obstacles found were: the positioning of the electro-acoustic transducers; the achievement of sufficient attenuation in a region far from the transformer, using a small number of control sources and error sensors (when the latter are positioned on the region of acoustic near-field); and the robust identification of the secondary path in a low signal/noise situation. The two former problems were dealt with, and some alternative solutions were analyzed. Genetic algorithms (GA) were used for the optimization of the transducers\' position. The performance of these algorithms is strongly related to the acoustical model used and it was verified that the Usry method, used for modelling the transformers primary field, did not result in an adequate estimate. Using a simplified model for the primary source, the importance of the cost function in the GA\'s performance was made evident. It was also verified that the joint optimization of transducers\' position provides the same result, and in shorter time, as the independent optimization of control source and error sensor positions. Simulations with a new virtual sensor strategy (based on windowing the control sources) show that it is possible to increase attenuation levels in a region far from the transformer, even with a small number of control sources and error sensors. Laboratory and field tests with an ANC system prototype were undertaken and the results of these tests are thoroughly discussed.