### Abstract

A method to characterize the surface impedance of materials is presented. The estimation is based on pressure measurements with a spherical microphone array. These measurements are used to reconstruct the sound pressure and particle velocity on the sample’s surface, from which the material’s impedance is inferred. The accuracy of the reconstruction is improved by using compressive sensing, where the wave field is represented with only a few components, ideally an

incident and a reflected wave. However, at low frequencies, diffraction from the edges contributes considerably to the sound field. This leads to a deterioration of the impedance estimation, which is clearly visible in initial experimental results. The proposed methodology makes it possible to characterize the edge effect, and subsequently compensate for it in the processing, emulating measurements on an infinite sample.

incident and a reflected wave. However, at low frequencies, diffraction from the edges contributes considerably to the sound field. This leads to a deterioration of the impedance estimation, which is clearly visible in initial experimental results. The proposed methodology makes it possible to characterize the edge effect, and subsequently compensate for it in the processing, emulating measurements on an infinite sample.

Original language | English |
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Title of host publication | Proceedings of the 22nd International Congress on Acoustics |

Number of pages | 10 |

Publication date | 2016 |

Article number | Paper ICA2016-506 |

Publication status | Published - 2016 |

Event | 22nd International Congress on Acoustics : Acoustics for the 21st century - Catholic University of Argentina, Buenos Aires, Argentina Duration: 5 Sep 2016 → 9 Sep 2016 http://ica2016.org.ar/ |

### Conference

Conference | 22nd International Congress on Acoustics |
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Location | Catholic University of Argentina |

Country | Argentina |

City | Buenos Aires |

Period | 05/09/2016 → 09/09/2016 |

Internet address |

### Keywords

- Impedance measurement
- Spherical array

## Cite this

Richard, A. P. A., Fernandez Grande, E., Brunskog, J., & Jeong, C-H. (2016). Impedance estimation of a finite absorber based on spherical array measurements. In

*Proceedings of the 22nd International Congress on Acoustics*[Paper ICA2016-506]