A Critical Study of the Precision of Measurement of Absorption Coefficients by Reverberation Methods

Sabine, Paul E.

doi:10.1121/1.1915551

Cited by 3 publications

(2 citation statements)

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“…1,2 Two standardized methods are followed to measure the properties of sound-absorbing materials, and both were initially proposed nearly a century ago. [3][4][5][6][7][8][9] The first is the impedance tube method [10][11][12][13] and the second is the reverberation chamber method. 14,15 Regarding the impedance tube, many improvements have been proposed to the early twentiethcentury standing wave tube apparatus.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of acoustical materials sound absorption coefficient under oblique incidence plane wave and diffuse field via Allard model inversion

Sciard,

Berry,

Sgard

et al. 2024

Building Acoustics

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A technique for estimating the sound absorption of materials under oblique incidence plane wave and diffuse field excitations is proposed. It requires a mobile loudspeaker and a pair of fixed microphones above a layer of absorbing material. Starting from sound pressure measurements made above the material surface for multiple source positions and by inverting Allard’s propagation model, the proposed method allows for the identification of two effective (or equivalent) parameters, namely, the complex effective density and the complex wave number. Obtaining these parameters makes it possible to estimate the sound absorption coefficient for a plane wave with any angle of incidence or under a diffuse acoustic field by summation over the angles. The results are compared to theoretical values calculated using the Johnson-Champoux-Allard model and to reference measurements obtained using an impedance tube, a small cabin, a large reverberant room, and a sound field synthesis method. One of the limitations of this method lies in the assumptions associated with the Allard model to describe the sound field above the material (assumed to be isotropic, homogeneous, of constant thickness, and to behave like an equivalent fluid). The main advantages are (1) that the sound absorption coefficient can be estimated under oblique incidence plane wave and diffuse acoustic field with values that are always in a physical range (between 0 and 1), and (2) that samples of the order of the square meter without specific preparation can be tested which reduces the constraints associated with impedance tube or reverberant room measurements.

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Section: Introductionmentioning

confidence: 99%

“…1,2 Two standardized methods are followed to measure the properties of sound-absorbing materials, and both were initially proposed nearly a century ago. 3–9 The first is the impedance tube method 10–13 and the second is the reverberation chamber method. 14,15…”

Section: Introductionmentioning

confidence: 99%

Estimation of acoustical materials sound absorption coefficient under oblique incidence plane wave and diffuse field via Allard model inversion

Sciard,

Berry,

Sgard

et al. 2024

Building Acoustics

View full text Add to dashboard Cite

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Schallausbreitung

Trendelenburg¹

1961

Einführung in Die Akustik

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Calibrating the Sabine and Eyring formulas

Prawda

Schlecht

Välimäki

2022

The Journal of the Acoustical Society of America

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Of the many available reverberation time prediction formulas, Sabine's and Eyring's equations are still widely used. The assumptions of homogeneity and isotropy of sound energy during the decay associated with those models are usually recognized as a reason for lack of agreement between predictions and measurements. At the same time, the inaccuracy in the estimation of the sound-absorption coefficient adds to the uncertainty of calculations. This paper shows that the error of incorrectly assumed sound absorption is more detrimental to the prediction precision than the inherent error in the formulas themselves. The proposed absorption calibration procedure reduces the differences between the measured and predicted reverberation time values, showing that an accuracy within ±10% from the target reverberation time values can be achieved regardless of the absorption distribution in a room. The paper also discusses the oft neglected air absorption of sound, which may introduce considerable bias to the measurement results. The need for an air-absorption compensation procedure is highlighted, and a method for the estimation of its parameters in octave bands is proposed and compared with other approaches. The results of this study provide justification for the use of the Sabine and Eyring formulas for reverberation time predictions.

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A Critical Study of the Precision of Measurement of Absorption Coefficients by Reverberation Methods

Cited by 3 publications

References 0 publications

Estimation of acoustical materials sound absorption coefficient under oblique incidence plane wave and diffuse field via Allard model inversion

Estimation of acoustical materials sound absorption coefficient under oblique incidence plane wave and diffuse field via Allard model inversion

Schallausbreitung

Calibrating the Sabine and Eyring formulas

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