Desenvolvimento de um escâner automatizado para medição sequencial de respostas ao impulso

Development of an automated scanner for the sequential measurement of impulse responses

Souza, G. A. Engenharia Acústica, Programa de pós-graduação em Engenharia Civil, Universidade Federal de Santa Maria, Santa Maria RS, Brasil, gabriel.azzuz@eac.ufsm.br

Fonseca, W. D’A. Engenharia Acústica, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil, will.fonseca@eac.ufsm.br

Brandão, E. Engenharia Acústica, Universidade Federal de Santa Maria, Santa Maria, RS, Brasil, eric.brandao@eac.ufsm.br

Resumo

Este artigo apresenta o desenvolvimento de um escâner automatizado para a tomada sequencial de medições de resposta ao impulso. O sistema usa o mesmo tipo de tecnologia de impressoras 3D, com uma base que move um sensor acústico nos eixos x, y e z. A movimentação do sensor é feita por motores de passo, controlados por um processador Arduino. Assim, um conjunto de M respostas ao impulso são medidas sequencialmente com o arranjo configurado. Com as M respostas ao impulso coletadas, é possível mapear a informação espacial do campo sonoro em uma série de £ ondas planas, utilizando a solução de um problema inverso com regularização de Tikhonov. O sistema desenvolvido é flexível, de forma que diversos experimentos podem ser executados com precisão. Como demonstração, a bancada é utilizada na medição in situ da impedância acústica. De posse das amplitudes complexas das £ ondas planas, pode-se reconstruir o campo acústico nas imediações do arranjo utilizado, o que permite a reconstrução da impedância de superfície do material sob teste.

Palavras-chaves:

medição de impedância

escaneamento do campo acústico

arranjo de microfones

decomposição em ondas planas.

Abstract

This paper presents the development of an automated scanner for measuring sequential impulsive responses. The system uses the same type of technology as 3D printers, with a base that moves an acoustic sensor along the x, y, and z-axis. The sensor displacement is accomplished with stepper motors, controlled by an Arduino processor. Thus, a set of M impulse responses are measured sequentially with a configured array. With the M impulsive responses collected, it is possible to map the spatial information in the sound field to a set of £ plane waves by solving the inverse problem with Tikhonov regularization. The built system is flexible, and different experiments can be executed accurately. This study focus on the in situ impedance measurement. Once one computes the complex amplitudes of the £ plane waves, the sound field in the vicinity of the array can be reconstructed, which allows the estimation of the surface impedance of a sound absorber.

Keywords:

impedance measurement

sound field sanning

array of microphones

plane-wave decomposition.

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