Using Sabine’s and sound power relation to study: The effect of diffusers on measured sound absorption

Abstract

The purpose of this study is to evaluate the effect of the number of diffusers placed in the same room, as well as the effect of diffusers with a flat area (8.4, 13.2, and 18 m²) on the calculated sound absorption coefficient in a reverberation room, when an iterative procedure based on the evaluation of the sound power level is applied (this is done by using the sound power equation and substituting with different values of equivalent absorption area on both sides of the transformed equation to reach the correct value for absorption area, which achieves equality on both sides of the equation in order to achieve the goal). The sound absorption coefficient at random incident of three materials having different degrees of absorption—has been measured in a reverberation room according to ISO 345: a highly absorbent material (sponge) a medium absorbent material (rubber) and a low absorbent material (wood).There is a noticeable convergence between the calculated and measured sound absorption coefficient from the usual ISO 354 procedure and from the sound power level equation from ISO 3741,when diffusers are present. The difference in sound power level is close to 1.0 dB depending on the position of the source with the diffuser area. Thanks to the diffusers effect, the difference between the measured and the calculated sound absorption coefficient can be considerably reduced.

Keywords

Sound absorption diffusers sound power estimation iteration equivalent absorption area

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References

Benedetto

Brosio

Spagnolo

. The effect of stationary diffusers in the measurement of sound absorption coefficients in a reverberation room: an experimental study. Appl Acoust 1981; 14(1): 49–63.

Toyoda

Sakamoto

Tachibana

. Effects of room shape and diffusing treatment on the measurement of sound absorption coefficient in a reverberation room. J Acoust Soc Technol 2004; 25(4): 255–266.

Nolan

Vercammen

Jeong

. Effect of different diffuser types on the diffusivity in a reverberation chamber. Proc Euronoise 2015; 191–196.

Drabek

Zalesak

. Reverberation chamber and its verification for acoustic measurements MATEC Web Conf 2016; 76: 05009.

Vercammen

. On the revision of ISO 354, measurement of the sound absorption in the reverberation room. In: Proceedings of 23rd international congress on acoustics ICA 2019, Aachen, Germany, 2019, pp. 3991–3997.

Lautenbach

Vercammen

MLS

. Volume diffusers in the reverberation room. In: Proceedings of 20th international congress on acoustics ICA 2010, Sydney, Australia, 2010, pp. 1–7.

Kim

Jeon

. Effect of diffusion conditions on absorption performance of materials evaluated in a reverberation chamber. Sustainability 2019; 11(6651): 1–16.

Berardi

Arau–Puchades

. Increasing reverberation time with diffusers: a new acoustic design for more sustainable halls. International Symposium on Room Acoustics, Toronto, Canada, 2013, pp. 1–9.

Stephenson

. Different assumptions - different reverberation formulae. Proceedings of Inter-Noise, New York, USA, 2012, pp. 1–12.

10.

Cops

Vanhaecht

Leppens

. Sound absorption in a reverberation room: causes of discrepancies on measurement results. Appl Acoust 1995; 46(3): 215–232.

11.

Vercammen

. How to improve the accuracy of the absorption measurement in the reverberation chamber. Proceedings of the International Symposium on Room Acoustics, ISRA, Melbourne, Australia, 2010, pp. 29–31.

12.

Mee

Vallis

. Improving sound diffusion in a reverberation chamber. In: Acoustics Conference, Australia, 2015, pp. 1–11.

13.

Lautenbach

Vercammen

. Can we use the standard deviation of the reverberation time to describe diffusion in a reverberation chamber? Proceedings of ICA 2013, Canada, 2013, pp. 1–7.

14.

Scrosati

Martellotta

Pompoli

, et al. Towards more reliable measurements of sound absorption coefficient in reverberation rooms: an inter-laboratory test. Appl Acoust 2020; 165: 107298.

15.

ISO 354:2003. Measurement of sound absorption in a reverberation room.

16.

Schroeder

. New Method of Measuring Reverberation Time. J Acoust Soc Am 1965; 37: 409–412.

17.

De Cesaris

Orazio

Morandi

, et al. Extraction of the envelope from impulse responses using pre-processed energy detection for early decay estimation. J Acoust Soc Am 2015; 138(4): 2513–2523.

18.

ISO 6926:2016. Requirements for the performance and calibration of reference sound source used for the determination of sound power levels.

19.

ISO 3741:2010. Determination of sound power levels and sound energy levels of noise sources using sound pressure — Precision methods for reverberation test rooms.

20.

Cucharero

Hänninen

Lokki

. Influence of sound-absorbing material placement on room acoustical parameters. Acoust J 2019; 1: 644–660.

21.

ISO 9613-1:1993. Acoustics - Attenuation of sound during propagation outdoors - Part 1: Calculation of the absorption of sound by the atmosphere.

22.

Zhang

Lee

. Diffuseness quantification in a reverberation chamber and its variation with fine-resolution measurements. Build J 2021; 11(519): 1–16.

23.

Ho Kim

Yong Jeon

. Effect of diffusion conditions on absorption performance of materials evaluated in reverberation chamber. Sustainab J 2019; 11(6651): 1–16.

24.

Mange

. The effect of mean free path on reverberation room measurement of absorption and absorption coefficients. Noise Control Eng J 2005; 53(6): 268–270.

25.

Bradley

Müller-Trapet

Adelgren

, et al. Effect of boundary diffusers in a reverberation chamber: standardized diffuse field quantifiers. J Acoust Soc Am 2014; 135(4): 1898–1906.