Noncontact Measurements of Sound Absorption Coefficient with a Pressure-velocity Probe, a Laser Doppler Vibrometer, and a Microphone Array | IEEE Conference Publication | IEEE Xplore

Noncontact Measurements of Sound Absorption Coefficient with a Pressure-velocity Probe, a Laser Doppler Vibrometer, and a Microphone Array


Abstract:

Kundt's tube and reverberant chamber are common methods for determining the sound absorption coefficient or acoustic impedance of materials. These measurement methodologi...Show More

Abstract:

Kundt's tube and reverberant chamber are common methods for determining the sound absorption coefficient or acoustic impedance of materials. These measurement methodologies are well-known and standardized, albeit not being practicable in-situ and requiring the isolation of samples of the material under test. Furthermore, Kundt’s tube results are affected by the size and the diameter of sample, and by the tube length, while reverberant chamber ones by the room dimensions and diffusiveness. In literature, noncontact techniques for sound absorption coefficient and acoustic impedance measurement are widely debated. In this paper, three different noncontact systems for measuring the sound absorption coefficient have been investigated: a pressure-velocity probe, a Laser Doppler Vibrometer, and a spherical microphone array featuring 64 capsules. The three methods have been evaluated through in-situ measurements of materials with known acoustic characteristics: Basotect G+ and Expanded Polystyrene. Furthermore, the results obtained with the standard test signal, i.e., white noise, are compared with the exponential sine sweep technique, which provides an increased signal to noise ratio, and allows for removing nonlinear high order distortions and acoustic reflections. As a main contribution of this work, it will be shown that microphone arrays are an optimal solution for measuring the sound absorption coefficient.
Date of Conference: 05-07 September 2023
Date Added to IEEE Xplore: 23 October 2023
ISBN Information:
Conference Location: Bologna, Italy

I. Introduction

Acoustical properties of an environment like reverberation time, speech transmission index (STI), or loudness level may have a significant impact on the listening experience. They can cause discomfort, reduce the attention and learning ability, and result in a negative user experience. Sound absorbers or diffusers are commonly employed to reduce the reverberation and to uniformly distribute the sound energy in a closed space. Hence, a precise evaluation of the material acoustic properties, such as the absorption coefficient and the impedance, is more and more important for the design of buildings, passive noise reduction treatments, but also cars [1]- [3] or theatres [4].

References

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