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Acoustical engineering: A complete academic undergraduate program in Brazil
Abstract
Acoustics is a broad field of knowledge that extends branches all over the physics of wave phenomena, psychology, natural sciences, and engineering. It is taught, in general, as part of engineering, physics, or architecture programs, or even in graduate programs specialized in the theme. In Brazil, acoustics was taught in graduate programs, until the creation of Acoustical Engineering in 2009, at the Federal University of Santa Maria, an integral undergraduate program dedicated to acoustics, audio, and vibration (lasting ten semesters). This article presents its complete academic program, its creation process, and the professional establishment of the acoustical engineer. In the following, the program of study and subjects are elucidated and detailed, and the teaching methodologies used are also discussed. The program employs several active learning strategies, like project-based learning, aiming to transform abstract into concrete knowledge. The interaction of the university, the acoustical engineer, and society is also presented and clarified. The placement of graduates in fields and their workplaces are presented as outcomes. As a fundamental part of the engineer's formation, the infrastructure used, whether state-of-the-art or cost-effective equipment, is detailed in the context of teaching and research. Finally, some of the ongoing research projects of the students are described.
... Previous studies have reported this presentation includes laboratory presentations, feasibility reports, progress/status reports, survey presentations, training lectures, and business reports as investigated by Disanza and Legge [13,14], Srinon [11] and Srinon et al., [12], Ferrer-Pardo et al., [15]. Rosalina [7], Seals [8], Benraghda et al., [16], Fonseca et al., [17] and Xian Ming [18] defined oral presentation as a partly spoken and visual form of communication that occurs in organisational settings, with the objective to transfer information, established as a formal assessment for the students. Fonseca et al., [17] further adds that such presentations are usually audience-friendly, highly casual, and very difficult for non-native English speakers to perform. ...
... Rosalina [7], Seals [8], Benraghda et al., [16], Fonseca et al., [17] and Xian Ming [18] defined oral presentation as a partly spoken and visual form of communication that occurs in organisational settings, with the objective to transfer information, established as a formal assessment for the students. Fonseca et al., [17] further adds that such presentations are usually audience-friendly, highly casual, and very difficult for non-native English speakers to perform. ...
The Final Year Project Presentation or FYPP is an essential academic oral presentation for tertiary students across various university courses and fields. Despite its importance, there exists a notable lack of comprehensive understanding about the genre, particularly about the conclusion section. This study aimed to investigate engineering students' perception of the good characteristics of the conclusion section in FYPP. A questionnaire survey was administered to a sample of 33 engineering students, who identified the following features as important components of the conclusion section: a summary of the final year project, presentation of overall findings, references to previous research, discussion of issues related to the final year project, restatement of the objective/focus, specific results, interpretation of results, significance of the results, limitations, counter-arguments, and an explanation of the final year project. The study reveals that students are aware of the various elements that make up the conclusion section and suggests that this knowledge can help them improve their FYPPs. By better understanding the genre expectations and characteristics, engineering students can present their final year project findings more effectively and demonstrate their mastery of the discipline.
... This study was supported by the Coordination for Higher Education Staff Development -Brazil (CAPES/PROEX) -Financing Code 001 and the National Council for Scientific and Technological Development (CNPq), under process 308653/2022-0. In addition, the authors would like to thank the support and infrastructure of the Acoustical Engineering Program (EAC) [22], the Graduate Program in Electrical Engineering (PPGEE), and the Graduate Program in Architecture, Urbanism, and Landscaping (PPGAUP), all affiliated with the Federal University of Santa Maria (UFSM). ...
Active participation of students in practical classes at universities significantly enhances the knowledge assimilation process. Within this context, this article presents the meticulous design and implementation of a turntable, with special attention to the fields of Electrical and Acoustical Engineering. The article explores the conceptual foundations and intrinsic procedures involved in the materialization of this instrument, emphasizing its relevance as a multidisciplinary pedagogical device. It is also worth noting that its prominence extends beyond practical training in engineering fields, permeating the realm of scientific research. The contribution of this work is twofold: initially, it outlines a sequential methodology for the construction of the turntable, optimized to be conducted by instructors and students under the paradigm of active learning methodologies. Subsequently, it presents practical cases arising from the versatile application of this tool, attesting to its significance and potential impact in the educational and technical domains of engineering.
... Many schools and universities are now utilizing digital technology and multimedia to aid in visualizing difficul and abstract physics concepts (Rahim et al., 2022;Sunaryo et al., 2022). Furthermore, many physics teachers are adopting project-based approaches (Yanti et al., 2019;Widyaningsih & Yusuf, 2019;Santyasa et al., 2020;Makkonen et al., 2021) and problem-based approaches (Fauzana, et al., 2019;Pane et al., 2021;Kanyesigye et al., 2022a;Kanyesigye, et al., 2022b;Fonseca et al., 2022) to motivate students and help them better understand physics concepts. ...
Metacognition refers to the capacity to comprehend and regulate one's own cognitive processes. By cultivating students' metacognitive skills in physics education, they will acquire the ability to understand and govern their own thinking. This, in turn, will enhance the effectiveness of physics instruction by fostering student engagement and enabling them to rectify their own errors. However, previous studies have revealed a scarcity of physics teachers who integrate metacognitive training into their teaching practices. Thus, the aim of this research is to investigate the extent to which high school physics teachers in the Riau Islands Province engage in metacognitive training for their students. Employing a qualitative approach with a phenomenological method, data was collected through interviews conducted with physics teachers from local high schools. This study's participants are physics teachers in the Kepulauan Riau Province. There are a total of 25 physics teachers participating in the study. The sampling technique employed in this research is purposive sampling. During these interviews, the researchers posed open-ended questions to elicit insights into physics teachers' experiences with the cultivation of metacognitive skills in their students during physics lessons. According to the study's findings, physics teachers in the Riau Islands Province are indeed training their students in indicators of metacognitive abilities. However, we observed that some teachers remain unaware that the exercises they assign inherently serve as indicators of metacognitive skills. This lack of awareness is attributed to a deficient understanding among teachers regarding the nature of metacognition.
O estudo de vibrações e seus efeitos causados em humanos e máquinas é de extrema importância para a engenharia. Sendo assim, diversas disciplinas do curso de Engenharia Acústica (EAC) da Universidade Federal de Santa Maria (UFSM) abordam conceitos a respeito do controle de vibrações. Nessa área de estudo, Absorvedores Dinâmicos de Vibrações (ADVs) são ferramentas eficazes e importantes para mitigar problemas, possuindo uma modelagem relativamente simples. Entretanto, devido à complexidade na montagem de uma bancada experimental, as aulas práticas sobre esses sistemas podem se tornar desafiadoras. Dessa forma, idealizou-se a criação de uma bancada didática para o estudo de ADVs, instrumentada utilizando equipamentos da EAC - como acelerômetros, martelos modais, excitadores modais, sistemas de aquisição etc. Por abranger também outras áreas do conhecimento (como processamento digital de sinais, instrumentação em acústica e vibrações, entre outras), a bancada tornou-se um objeto de estudo multidisciplinar. Assim, foi possível analisar o comportamento de um ADV tanto de forma visual quanto no processamento dos dados medidos (aceleração e deslocamento, no domínio do tempo e da frequência), comparando-os com a teoria vista em sala de aula. Por fim, os resultados obtidos corroboram com a teoria e demonstram a robustez do projeto e construção da bancada.
Este artigo explora as capacidades da câmera Sony PlayStation 3 Eye, equipada com quatro microfones integrados (em linha, separados por 2 cm) e uma câmera. Esse aparato pode ser utilizado para aplicações acústicas como detecção de presença, detecção de rosto, localização de fontes sonoras, cancelamento de eco, supressão de ruído de fundo, beamforming e transcrição de áudio. Considerando seu custo acessível, em torno de 5-10 dólares, o dispositivo oferece uma solução viável para projetos de aquisição sonora de baixo custo. Inicialmente, neste trabalho, foram discutidas as especificações técnicas da PS Eye, destacando suas configurações e características. Em seguida, foram detalhados os métodos de conexão e aquisição de dados dos canais utilizando plataformas como DAW (Digital Audio Workstation) e Matlab. Testes de desempenho foram realizados para estabelecer a faixa de operação acústica do arranjo de microfones, especificamente sua resposta em frequência, faixa dinâmica e direcionalidade. Resultados indicaram uma resposta em frequência aproximadamente plana até 2 kHz, com uma faixa dinâmica de 55 dB e uma resposta direcional simétrica e consistente. Por fim, observa-se que a PS Eye representa uma alternativa econômica e versátil para projetos de captação e análise acústica, com grande potencial para aplicação em ambientes educacionais e no desenvolvimento de protótipos.
Os ginásios esportivos são ambientes comuns em diversas comunidades do mundo todo. No Brasil, grande parte da população tem acesso a esses espaços desde o ensino primário, normalmente por meio de aulas de educação física e eventos esportivos locais. Entretanto, a maioria desses ambientes não proporciona um conforto acústico adequado para as diversas atividades realizadas. A Universidade Federal de Santa Maria oferece o curso de graduação em educação física e conta com dois edifícios caracterizados como ginásios esportivos. Em ambos, são ministradas aulas e utilizados diversos equipamentos para o ensino da área. Este artigo teve como objetivo caracterizar o campo acústico do Ginásio Didático II a partir da medição de tempo de reverberação conforme a norma ABNT NBR ISO 3382-1:2017, utilizando o método de resposta impulsiva integrada. Por meio da comparação com as normas BB93 e PN-B-02151, buscou-se verificar se os valores obtidos atendem aos requisitos estabelecidos, bem como obter e analisar o índice de transmissão da fala. A partir dos resultados, observou-se que o Ginásio Didático II não atende às normas consideradas. Investigações mais aprofundadas serão realizadas posteriormente para abordar essas inadequações.
This research presents a strategy to enhancing sound absorption in porous acoustic metamaterials through the optimization of micro-duct networks. The study employs a combination of analytical and numerical methods, systematically adjusting micro-duct diameters within a 2D grid to optimize absorption coefficients at specific frequency bands. The Finite Element Transfer Method (FETM) is utilized for modeling, supported by a multi-objective function influenced by the surface impedance of the network. This approach ensures practical applicability and manufacturability of the designed metamaterial. A significant aspect of the study is the development of an analytical mobility matrix for each microduct, integrated through the Transfer Matrix Method using the visco-thermal dissipation theory. This integration results in a physically coherent model, for which a semi-analytical sensitivity analysis related to the microduct diameters can be directly performed. The optimization employs the Method of Moving Asymptotes (MMA), effectively managing the complexity associated with a large number of design variables. Subsequently, the optimized structure is adapted into a 3D grid, facilitating prototype creation using Additive Manufacturing Technology (AMT) with a specific polymer material. The research methodology is validated through four distinct test cases, each demonstrating the efficacy and adaptability of the optimization tools and techniques. Experimental validation, conducted using an impedance tube, indicates a significant shift in the first absorption maximum from 2500 Hz to 1000 Hz, achieved without altering the material thickness. Additional validation through 3D Finite Element Method (FEM) modeling, which includes visco-thermal effects, further confirms the acoustic efficiency of the final designs. While the potential for achieving lower sub-wavelength conditions is recognized, the study opts for simpler structures, considering the current limitations of 3D printing technology. This study contributes to both theoretical understanding and practical application in acoustic material design, emphasizing the potential for customizing materials to specific frequency ranges. The integration of FETM modeling with MMA provides a systematic and effective approach for optimizing acoustic materials, particularly in enhancing absorption at lower frequencies.
Este documento contém instruções para a escrita de artigos para o XXX Encontro da Sociedade Brasileira de Acústica (Sobrac). Esse campo é destinado ao resumo do artigo que deve ter entre 180 e 300 palavras. O resumo, palavras-chave, title, abstract e keywords devem ser colocados na primeira página do artigo, buscando não se estender para a segunda página. O resumo deve fazer uma apresentação concisa do artigo técnico científico, contendo, uma introdução, o objetivo, uma síntese da metodologia, o principal resultado e a principal conclusão (preferencialmente nessa ordem). Não é necessário separar em itens ou seções dentro do resumo. Assim, o leitor pode conhecer a essência do conteúdo do artigo. Lembre-se que o resumo é como o trailer de um filme, as pessoas ficarão interessadas em ler completamente o artigo se o resumo lhes interessar. O resumo não deve conter informações novas não contidas no artigo; abreviações indefinidas; discussão prévia de outra literatura; referências e citações e excesso de detalhes acerca dos métodos empregados. Ele também não é o parágrafo de introdução do documento, isso deve ser colocado no início do texto. Utilize apenas informações úteis e relevantes, faça um exercício de empatia com o possível leitor interessado. Para se obter um resumo coeso, elegante e de acordo com o artigo, escreva uma prévia, realize a escrita completa do documento e, ao final, revise-o observando se o conteúdo dele reflete de forma consistente o teor do documento. Seguindo o resumo, o autor deve listar até cinco palavras-chave (evite colocar as mesmas palavras que formam o título do artigo). Após essa etapa, há ainda o título, resumo e palavras-chave em inglês. Palavras-chave: artigo técnico, Sobrac, acústica, vibrações. Instructions and paper template for the XXX Meeting of the Brazilian Acoustics Society (Sobrac) Abstract This document contains instructions for writing papers for the XXX Meeting of the Brazilian Society of Acoustics (Sobrac). This field is intended for the abstract of the article, which must contain between 180 and 300 words. The elements resumo, palavras-chave, title, abstract, and keywords should constitute the first page (i.e., avoid extending them to the second page). The abstract should make a concise presentation of the scientific-technical article, containing an introduction, the objective, a synthesis of the methodology, the main result, and the final conclusion (preferably in that order). Separate items or sections are not required within the abstract. Thus, the reader may acknowledge the essence of the article content. Remember that the abstract is like a movie trailer, people will consider reading the complete article if the abstract is interesting. The abstract should not contain new information not contained within the article; undefined abbreviations; previous discussion of another literature; references and citations; or excessive detail about the methods employed. It is also not the introductory paragraph of the work; this should be placed at the beginning of the text. Use only relevant and useful information, exercising empathy with prospective readers. For a cohesive and elegant abstract that represents the article, write a preview, complete the paper, and then review it by looking at whether its content consistently reflects the content of the document. Following the abstract, the author should list up to five keywords (avoid using the same words contained in the article's title). After this step, there are also title, abstract, and keywords in English.
Auralização é o processo de criação ou captura de um cenário auditivo e é comumente associada à audição biauricular, que permite a localização de fontes sonoras no espaço. Este artigo apresenta ferramentas projetadas para facilitar a geração de auralizações adaptativas com base na posição do ouvinte, permitindo comparações em tempo real entre Funções de Transferência Relacionadas à Cabeça (HRTFs). São abordados os principais algoritmos para convolução por partes, como o overlap-add (OLA), overlap-save (OLS) e uniformly partitioned overlap-save (UPOLS), discutindo suas vantagens e desvantagens em termos de eficiência computacional e qualidade de áudio resultante. Suas implementações computacionais são também aclaradas, visto que oferecem recursos de convolução em tempo real computacionalmente competentes. O trabalho também destaca a técnica de transição suave entre filtros convoluídos (crossfading), para garantir uma reprodução contínua e natural do som. Além disso, é discutido um sistema de rastreamento da posição da cabeça do ouvinte (wireless) utilizando imagens de vídeo e inteligência artificial, que permite a adaptação da auralização à posição do ouvinte em tempo real. Por fim, é apresentado um sistema que integra ambas as ferramentas — chamado de máquina de auralização —, destinado a estudos de validação subjetiva, como a análise de métodos de individualização HRTF ou a comparação de projetos de acústica de salas. Neste estudo, o funcionamento adequado do projeto foi revelado por meio de um teste-piloto. Cabe ainda salientar que as ferramentas são distribuídas gratuitamente e podem ser melhoradas de forma colaborativa pela comunidade científica. Observa-se ainda que as ferramentas e técnicas apresentadas neste trabalho são fundamentais para a criação de ambientes sonoros verossímeis em aplicações como jogos, realidade virtual, cinema e produção musical.
Power generation through wind turbines has been increasing worldwide, leading to new challenges regarding their surrounding soundscapes. In this sense, standards and legislations were created to rule the installation of wind turbines, accounting for the well-being of people living in their neighborhoods. From 2015 to 2019, the Ordinance Inmetro-MDIC nº168 (from 23/05/2105) was operative, which spoke about the ``Conformity Assessment Requirements for Wind Turbines'' including details on their electrical and acoustic parameters. Concerning the acoustics part, the document pointed to requirements of the international standard IEC 61400 -- \textit{Wind turbine generator systems -- Part 11: Acoustic noise measurement techniques}. This work aims to show a simplified study of the IEC~61400. Thereunto, a scaled rotative prototype was built. Its sound generation was carried out by two wireless loudspeakers axisymmetric positioned on the blades, which were moved by a DC motor controlled by an Arduino via Matlab. The prototype’s noise emission was evaluated following the IEC guidelines. In addition, acoustic imaging studies were carried out to compare techniques involving fixed and moving focus, along with time-windowing. To that, UFSM’s Acoustical Engineering Beamap Toolbox was used (fixed focus and time-windowing), along with Acoular (dynamic results), developed at the Technical University of Berlin. Ultimately, the principles of the standard’s methods were successfully applied. Moreover, it was possible to show the effectiveness of moving focus acoustical imaging algorithms (via comparison against fixed focus algorithms).
Beamforming is an acoustic imaging technique widely applied in sound source localization. Its basic principles rely upon an array of receivers (usually microphones, in acoustics) that sample the sound field, thus creating time data, which is processed via computational digital signal processing (DSP) techniques. Such application integrates different branches of knowledge, beginning with acoustics, passing through instrumentation and programming, and ending in DSP. Furthermore, concepts like windowing and sampling are addressed across time and spatial domains. Thus, as a university assignment, the technique has the potential role to gather distinctive topics to consolidate abstract knowledge into concrete ones. This article presents the experience of using Active Learning (AL) approaches in teaching acoustical beamforming to undergraduate students of the Acoustical Engineering (EAC) Program at the Federal University of Santa Maria (UFSM), in southern Brazil. These techniques focus upon increasing knowledge retention, being the Problem-Based Learning (PBL) one of its family. The strategy is the \textit{practice by doing}, combining the learned knowledge with real situations. In EAC, beamforming is taught along two front lines, one is within the subject of acoustical experiments — exploring pre- and post-processing, as well instrumentation and measurement — and during students' Bachelor's Theses, where there is also space to include research and prototypes.
Sound emissions by rotating machinery are often connected to rotating acoustic sources. Efficient control of these emissions – whether by simply reducing them or by shaping their spectral characteristics – requires knowledge about the underlying sound generating mechanisms as well as the contribution of separate sources to the total radiation. The detection of sound sources is subject of ongoing research. In the presence of multiple sources, using microphone array methods for their spatial separation is state of the art.
In this thesis, several novel data processing methods are presented whose application provides new insights based on acoustic measurements with circular array arrangements. Aside from the localization of rotating sound sources, it is shown how these measurements can be used for the detection of occurring rotational speeds and for the isolation of different spectral characteristics. Most importantly, the presented data processing allows the separation of acoustic features even if multiple sources with different rotational speeds are present in one data set.
The general applicability of the methods and their limitations are investigated with the help of simulated acoustic data. For demonstrating their practical capabilities, two experimental setups featuring axial fans are evaluated: one with a microphone ring array measuring the sound radiated into a freefield and the other with a ring of wall-mounted microphones within a cylindrical duct. It is shown that with the new methods, previously inaccessible knowledge about present acoustic sources and the underlying sound generating mechanisms can be gained.
In this paper we propose the use of neural networks to predict the sound absorption coefficient spectra of finite porous samples with microphone arrays. The main goal is to train a model that can effectively mitigate the errors caused by the finite size effect. A convolutional neural network architecture is used to map the array data to the absorption coefficient at five frequencies. The training, validation and test data are numerically produced with a boundary element method; modelling a baffled, locally reacting porous absorber on a rigid backing with a Delany-Bazley-Miki model, for varying sample size, thickness, flow resistivity, incidence angle and frequency. The strength of using machine learning in this context is that no hypotheses are made about the sound field or the absorber, as the networks learn the necessary relationships from the data. We show that the network approximates well the absorption coefficient, as if the sample was infinite, in a wide range of cases.
Com o objetivo conscientizar a população sobre os efeitos nocivos do ruído para audição, saúde e qualidade de vida o League for the Hard of Hearing, atualmente, Center for Hearing and Comunication, propõe um evento que promove 60 segundos de silêncio para destacar o impacto do ruído na vida cotidiana, proporcionando aos participantes uma pausa e uma oportunidade de conscientização sobre um problema que impacta a saúde pública mundial. Trata-se do International Noise Awareness Day (INAD) ou Dia Internacional de Conscientização sobre o Ruído que ocorre em uma data móvel, sempre na quarta-feira da quarta semana do mês de abril, desde 1996. Além dos Estados Unidos, a campanha é muito difundida na Alemanha, Espanha, Chile, Holanda, Suíça, Itália, Portugal, entre outros. No Brasil, O INAD acontece desde 2008 com a incorporação de outras atividades, respeitando a diversidade do território nacional e criatividade dos parceiros locais, como por exemplo, reuniões com autoridades governamentais e ambientais, distribuição de protetores auditivos, estratégias educativas e avaliação do ruído e da audição. A participação de colaboradores autônomos e institucionais, simpatizantes e organizações de representatividade de classes tem sido crescente. Este capítulo sintetiza a trajetória de 13 anos do INAD no Brasil, a partir do resgate dos lemas e temas propostos a cada edição, descrição do alcance da campanha e anúncio das pretensões futuras.
Auralization is a well-known method used to create virtual acoustic scenarios. This work elaborates techniques for the Binaural Room Impulse Response (BRIR) extraction of the interior of a passenger car cabin. As a novelty, this study developed a binaural recorder based upon digital MEMS (micro-electro-mechanical system) microphones combined with an Arduino compatible microcontroller (Teensy). To improve the recordings, spectral corrections to the acquired data were carried out. The system is compact and cost-effective, creating an advantage for those measuring different source-receiver positions. For this paper, several combinations of BRIRs were tested, including combinations of binaural recordings for ambiance. Finally, equipped with the BRIRs database, it was possible to auralize different situations in real-time, for example, a conversation between two people (with the possibility to switch/tune background music and engine sound on and off). Furthermore, it was also possible to combine sources and receivers simultaneously with a contactless camera head tracker. Listening tests revealed that the spatial impression was preserved, rendering exceptional results as a virtual environment.
Noise assessment and monitoring are essential parts of an acoustician's work. They help to better understand the environment and propose better solutions for noise control and urban noise management. Traditionally, equipment used to carry out these tasks is standardized and often times is considered expensive for the early career professional. This study has developed a high-quality (and cost-effective) prototype for an embedded noise monitoring device based upon a digital I2S MEMS microphone and an Arduino compatible microcontroller named Teensy. Its small size and low power consumption are also advantages designed for the project. The system captures and processes sound in real-time and computes A and C frequency-weighted equivalent sound levels, along with time-weighted instant levels (with a logging interval of 125 ms). Part of the software handles the audio environment, while the biquadratic IIR filters present in the Cortex Microcontroller library are responsible for the frequency- and time-weightings - using floating-point for enhanced precision. The prototype performance was compared against a Class 1 Sound Level Meter (SLM), rendering very similar results to tested situations, proving a powerful and reliable tool. Improvements to the system and further testing will be conducted to refine its functioning and characterization. Ultimately, the prototype demonstrated promising performance, achieving LAeq values within a +/-0.5 dB margin over the Class 1 SLM and confirming its potential as a cost-effective solution for noise monitoring and assessment.
Binaural rendering is a technique that seeks to generate virtual auditory environments that replicate the natural listening experience, including the three-dimensional perception of spatialized sound sources. As such, real-time knowledge of the listener’s position, or more specifically, their head and ear orientations allow the transfer of movement from the real world to virtual spaces, which consequently enables a richer immersion and interaction with the virtual scene. This study presents the use of a simple laptop integrated camera (webcam) as a head tracker sensor, disregarding the necessity to mount any hardware to the listener’s head. The software was built on top of a state-of-the-art face landmark detection model, from Google’s MediaPipe library for Python. Manipulations to the coordinate system are performed, in order to translate the origin from the camera to the center of the subject’s head and adequately extract rotation matrices and Euler angles. Low-latency communication is enabled via User Datagram Protocol (UDP), allowing the head tracker to run in parallel and asynchronous with the main application. Empirical experiments have demonstrated reasonable accuracy and quick response, indicating suitability to real-time applications that do not necessarily require methodical precision. Furthermore, cross-validation with existing hardware head trackers revealed an adequate agreement on measured head orientation, confirming its potential as a contactless head tracking device.
No contexto de tecnologia biauricular, tanto para reprodução quanto para captação de sinais biauriculares é extremamente importante ter a informação de localização do receptor, que pode ser uma pessoa ou um manequim, em termos de rotação, translação ou ambos. Para isso, muitas vezes são utilizados dispositivos de rastreamento que, mais especificamente para o rastreamento da cabeça, são chamados de head trackers. Esses instrumentos têm como finalidade fornecer dados sobre a orientação da cabeça de um ser humano, que podem ser utilizados então em aplicações como a de gerar movimentos em um ambiente virtual a partir de movimentos reais ou fornecer informações de ângulo em medições de Head Related Transfer Functions e Head Related Impulse Response, sinais que descrevem objetivamente a difração citada anteriormente, de forma que se tenha, para cada posição angular, um sinal diferente armazenado. O objetivo desse trabalho é apresentar o estudo realizado na Universidade Federal de Santa Maria (UFSM) no ano de 2018 para desenvolver dois sistemas utilizando um aparelho de rastreamento, baseado no projeto Mr. Head Tracker , sendo eles uma cadeia de reprodução, cujo a proposta foi utilizar bancos de dados de HRTF para gerar áudios biauriculares a partir da informação de posição gerada pelo head tracker, e uma cadeia de medição biauricular, cujo intuito foi utilizar o dispositivo para fornecer informação de ângulo entre fonte sonora e manequim em um set up simplificado de medição de HRTFs. Será apresentada a metodologia adotada para tais procedimentos, desde a etapa de implementação das rotinas computacionais até equipamentos utilizados, assim como o procedimento de pós processamento necessário para chegar em resultados adequados da cadeia de medição. Além disso, são apresentados um passo-a-passo para a utilização do aparato construído com softwares computacionais como Matlab, tal qual da sua construção em si, e os resultados alcançados a partir dos procedimentos realizados com os sistemas propostos. Tais resultados demonstraram que foi possível chegarem um erro médio de aproximadamente 10 ° para a localização de fontes com o sistema de reprodução desenvolvido e que a cadeia simplificada de medições de HRTFs chegou em resultados bastante satisfatórios, em que as curvas obtidas se assemelham bastante à referência utilizada e apresentam uma baixa Spectral Distortion, parâmetro utilizado para comparação. Porém, considerando a falta de ambiente anecoico ideal e de instrumentação necessária, nova medição poderá ser feita para chegar a valores ainda melhores. De forma geral, o head tracker demonstrou funcionar de maneira adequada ambas as cadeias, se demonstrando extremamente útil para tais aplicações.
The prediction of the sound absorption coefficient in diffuse field conditions is of great interest to an acoustic project. Foams and granular materials like porous concrete have been used in many internal or external applications as sound absorbers. However, many doubts have regularly been discussed in scientific literature. The simple use of experimental impedance tube methods, that consider only the incident acoustic plane waves, is not equivalent to the experimental measurement in a reverberant room, which is necessary for a correct characterization of a given constructive solution. The scientific community has explored several methods to predict and approximate the sound absorption coefficient in diffuse field conditions, using only acoustic plane wave data. However, many of them do not allow a realistic approximation of the reverberant room measured data. Therefore, two numerical models are herein proposed which consider the porous media on the fluid-equivalent theory, first, a two-dimensional (2D) finite element method, and, second, a three-dimensional (3D) boundary element method (BEM). These methods are compared with analytical equations and experimental data from the reverberant room, studying the influence of the porous material panel size in the sound absorption coefficient in diffuse field conditions. To illustrate the proposed method's practical interest, the BEM 3D model was used to determine the diffuse field's sound absorption coefficient for finite-sized panels of porous concrete. This test was done for plane panels and for slit-like surfaces to highlight the possibilities of the proposed method.