Conception d’antennes de microphones sphériques pour la localisation de sources acoustiques et étude de l’influence de l’effet de diffraction sur les images acoustiques

Abstract

Prolonged exposure to noise in the workplace can lead to physiological and psychosocial disorders. In order to protect workers, the noise source can be eliminated, substituted or modified. To implement control measures at the source, it must be localized. In a workplace environment, an acoustic imaging system (AIS) can be used. An AIS is composed of a spherical microphone array (SMA), a camera and a beamforming algorithm. Depending on the type of beamforming algorithm, the SMA can be either rigid or open. A rigid array may cause the scattering of the acoustic wave, while for an open array, those effects are generally neglected. The development of an AIS is a complex task since its performance depends on the algorithm, the type of SMA, the number of microphones and the array geometry. During the development stage of an AIS, an SMA that allows for the installation of multiple microphones in various geometries is required. Also, the in fluence of the scattering effect caused by a rigid or open SMA can affect the acoustic images and must be assessed. This research work is part of a joint project with the IRSST, ÉTS and UdeS aimed at developing an AIS for real-time localization of acoustic sources in workplace environments. The first objective is the design of two modular SMA that allows for the installation of many microphones. The second objective is to study the influence of the scattering effect from a rigid SMA on acoustic images and to verify that the scattering effects of an open SMA are negligible. Two modular open SMA have been designed and manufactured. These SMA allow for the installation of a large number of microphones with more than 500 possible positions on the spherical support. Subsequently, a finite element model simulating the interaction of an acoustic wave with the structure of an SMA was developed. This model provides numerical microphone signals, which are then used to generate acoustic images with a beamforming algorithm. The images compared to assess the influence of the scattering effects. The results show that the scattering effects of a rigid SMA with the conventional beamforming in the frequency domain (CBF) algorithm are a smaller mainlobe and higher side lobes levels. The scattering effects caused by an open SMA were compared to a theoretically empty SMA and were deemed negligible.

Date	27 Oct 2023
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Olivier Doutres (Supervisor) & Franck Sgard (Co-supervisor)