Method of deriving the acoustic impedance and sound absorption coefficient of materials by manipulating electrical impedance of a loudspeaker

Sejin Doo

doi:10.7776/ASK.2021.40.3.254

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2021 Vol.40, Issue 3 Preview Page

Research Article

Method of deriving the acoustic impedance and sound absorption coefficient of materials by manipulating electrical impedance of a loudspeaker 스피커의 전기적 임피던스를 이용한 시료의 음향임피던스와 흡음계수 도출 기법

31 May 2021. pp. 254-260

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Abstract

When measuring the sound absorption coefficient of a specimen, a reverberation room which is costly or an impedance tube which has limitations in measuring low frequencies have been engaged. In this paper, a new measurement method of acoustic impedance or sound absorption coefficient has been suggested, which does not need microphones and only uses electrical impedance measurement data and derived Thiele/Small parameters of a speaker. The theory of this method has been described using equivalent circuit of the loudspeaker and acoustic properties of a test specimen are measured to demonstrate the validity of this method. It was confirmed that this method can easily measure the sound absorption coefficient in the low frequency band, which was previously difficult to trust. The advantages, limitations, and applicability of this method are discussed.

Keywords

Sound absorption

Acoustic impedance

Speaker

Equivalent circuit

Measurement

시료의 흡음률 측정을 위해서는 비용이 많이 드는 잔향실 혹은 저주파수에서의 측정에 한계가 있는 임피던스 튜브를 사용한다. 본 논문에서는 마이크로폰을 사용하지 않고 단지 스피커 임피던스와 이로부터 도출된 Thiele/Small 변수만을 사용하여 시료의 음향임피던스와 흡음률을 구하는 기법을 제안하였다. 스피커의 등가회로를 이용하여 이 방법의 이론을 설명하였으며, 시료의 측정을 통하여 본 방법의 유효성을 증명하였다. 본 방법은 기존에 신뢰하기 어려웠던 저주파 대역에서의 흡음률을 매우 쉽게 측정할 수 있음을 확인하였다. 본 방법의 장점과 제한사항, 그리고 응용 분야에 대해서 검토하였다.

키워드

흡음

음향 임피던스

스피커

등가회로

측정

References

ISO 354, Acoustics -Measurement of Sound Absorp tion in a Reverberation Room, 2003.

ISO 10534-2, Acoustics - Determination of Sound Absorption Coefficient and Impedance in Impedance Tubes - Part 2, 1998.

J. Y. Chung and D. A. Blaser, "Transfer function method of measuring in-duct acoustic properties. Part I: Theory," J. Acoust. Soc. Am. 68, 907-913 (1980). 10.1121/1.384778

J. Y. Chung and D. A. Blaser, "Transfer function method of measuring in-duct acoustic properties. Part II: Experiment," J. Acoust. Soc. Am. 68, 914-921 (1980). 10.1121/1.384779

A. Farina and A. Torelli, "Measurement of the sound absorption coefficient of materials with a new sound intensity technique," Proc. AES 102^th Convention, paper no. 4409 (1997).

D. Shearer, Measuring absorption below 100Hz with a P-U sensor, (Master's. Thesis, South Bank University, 2016).

R. Boulandet, "Sensorless measurement of the acoustic impedance of a loudspeaker," Proc. 23rd ICA. 7353- 7360 (2019).

L. E. Kinsler, A. R. Frey, A. B. Coppens, and J. V. Sanders, Fundamentals of Acoustics, 4^th ed (Wiley, New York, 1999), pp. 184-187.

X. Wang and Y. Xiang, "Probes design and experimental measurement of acoustic radiation resistance," J. Acoust. Vib. 22, 252-259 (2017). 10.20855/ijav.2017.22.2471

Information

Publisher :The Acoustical Society of Korea
Publisher(Ko) :한국음향학회
Journal Title :The Journal of the Acoustical Society of Korea
Journal Title(Ko) :한국음향학회지
Volume : 40
No :3
Pages :254-260
Received Date : 2021-03-22
Accepted Date : 2021-05-11
DOI :https://doi.org/10.7776/ASK.2021.40.3.254

The Journal of the Acoustical Society of Korea ISSN:1225-4428(Print) 2287-3775(Online) 한국음향학회지

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