Influence of the Scattering Effect on Acoustic Image Obtained with a Spherical Microphone Array

Authors

  • Julien St-Jacques École de Technologie Supérieure, CA
  • Kevin Rouard École de Technologie Supérieure
  • Franck Sgard Institut de recherche Robert-Sauvé en santé et en sécurité du travail
  • Hugues Nélisse Institut de recherche Robert-Sauvé en santé et en sécurité du travail
  • Alain Berry Université de Sherbrooke
  • Nicolas Quaegebeur Université de Sherbrooke
  • François Grondin Université de Sherbrooke
  • Loic Boileau Université de Sherbrooke
  • Olivier Doutres École de Technologie Supérieure
  • Thomas Padois Institut de recherche Robert-Sauvé en santé et en sécurité du travail,

Abstract

Longterm exposure to noise in the workplace can lead hearing loss and other psychosocial effects. Among the most effective noise reduction methods is to apply efforts directly at the source. To do so, each source must be characterized by their spatial location and contribution. In the workplace, a Spherical Microphone Array (SMA) can be used. When the microphones are held on a wireframe structure or on thin rods, the SMA is considered acoustically transparent, and the Conventional Beamforming in the Frequency domain (CBF) algorithm can be used. The CBF, however, does not compensate for the scattering effect of a diffracting object. On the other hand, rigid SMAs are usually made of a solid sphere with flush-mounted microphones and may scatter the acoustic waves. Although the literature has shown the advantages of using a rigid SMA with the spherical harmonics decomposition, the influence of the scattering effect on the acoustic image when not accounted for remains under-examined. This study aims to assess the influence of the uncompensated scattering effects on acoustic images obtained with a SMA. Images obtained with a rigid SMA are compared to those obtained from a theoretical perfectly transparent SMA using the CBF. First, a spherical wave field is simulated using a finite element analysis model to generate the microphone signals for both SMAs. Then, the images are generated using the CBF and three image quality criteria are used to assess the scattering effects, i.e., the ellipse area ratio, the mainlobe-to-sidelobe ratio and the mainlobe level. Results show that the influence of the scattering effect, if not corrected, will reduce the width of the mainlobe and amplify the level of the sidelobes. The effect on the estimated source level is not significant in this case.

Additional Files

Published

2023-10-09

How to Cite

1.
St-Jacques J, Rouard K, Sgard F, Nélisse H, Berry A, Quaegebeur N, Grondin F, Boileau L, Doutres O, Padois T. Influence of the Scattering Effect on Acoustic Image Obtained with a Spherical Microphone Array. Canadian Acoustics [Internet]. 2023 Oct. 9 [cited 2024 Oct. 3];51(3):180-1. Available from: https://jcaa.caa-aca.ca/index.php/jcaa/article/view/4075

Issue

Section

Proceedings of the Acoustics Week in Canada

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