Specific Normal Impedances and Sound Absorption Coefficients of Material

Sabine, Paul E.

doi:10.1121/1.1916105

Cited by 6 publications

(3 citation statements)

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“…Reasons for the overestimation have been widely accepted to be the finite size of samples and the edge diffraction. [7][8][9][10][11][12] To match the theoretical values with measured data, several works have been studied. Concerning the sound transmission loss, de Bruijn 13 addressed the influence of the degree of diffusivity in measurement conditions.…”

Section: ͑1͒mentioning

confidence: 99%

A correction of random incidence absorption coefficients for the angular distribution of acoustic energy under measurement conditions

Jeong

2009

The Journal of the Acoustical Society of America

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Most acoustic measurements are based on an assumption of ideal conditions. One such ideal condition is a diffuse and reverberant field. In practice, a perfectly diffuse sound field cannot be achieved in a reverberation chamber. Uneven incident energy density under measurement conditions can cause discrepancies between the measured value and the theoretical random incidence absorption coefficient. Therefore the angular distribution of the incident acoustic energy onto an absorber sample should be taken into account. The angular distribution of the incident energy density was simulated using the beam tracing method for various room shapes and source positions. The averaged angular distribution is found to be similar to a Gaussian distribution. As a result, an angle-weighted absorption coefficient was proposed by considering the angular energy distribution to improve the agreement between the theoretical absorption coefficient and the reverberation room measurement. The angle-weighted absorption coefficient, together with the size correction, agrees satisfactorily with the measured absorption data by the reverberation chamber method. At high frequencies and for large samples, the averaged weighting corresponds well with the measurement, whereas at low frequencies and for small panels, the relatively flat distribution agrees better.

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Section: ͑1͒mentioning

confidence: 99%

A correction of random incidence absorption coefficients for the angular distribution of acoustic energy under measurement conditions

Jeong

2009

The Journal of the Acoustical Society of America

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“…Various guesses have been made, [Refs. [4][5][6][7][8][9][10] with the oldest being the normal impedance assumption of Rayleigh, ca 1877, [4].…”

Section: Interesting Results Were Obtained From Tests (D) and (E)mentioning

confidence: 99%

Acoustical performance of some floor covering for hospitals

Winzer¹

1969

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“…Measured absorption coefficients are overestimated for small absorber samples and sometimes exceed unity, even for a nearly locally reacting surface. Reasons for higher measured absorption coefficients have been widely accepted to be the finiteness of samples and the edge diffraction [7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Directional distribution of acoustic energy density incident to a surface under reverberant condition

Jeong

2008

The Journal of the Acoustical Society of America

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Most acoustic measurements are based on the assumption of ideal conditions. One such ideal condition is a diffuse and reverberant field. In practice, a diffuse sound field cannot be achieved in a reverberation chamber. Particularly, the directional diffusion, which means the uniform angular distribution of incident energy onto surfaces, cannot be satisfied. Angle dependence of incident energy density was simulated by the phased beam tracing method by changing room shapes and source positions. It was found that acoustic energy density decreases with the angle of incidence. The shape of the averaged angular distribution is similar to the Gaussian distribution. Long distance between the source and the target surface highlights the normally incident components. To get a fairly uniform distribution, the acoustic centre of the source should be close to and aligned with the periphery of the absorption sample.

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Specific Normal Impedances and Sound Absorption Coefficients of Material

Cited by 6 publications

References 0 publications

A correction of random incidence absorption coefficients for the angular distribution of acoustic energy under measurement conditions

A correction of random incidence absorption coefficients for the angular distribution of acoustic energy under measurement conditions

Acoustical performance of some floor covering for hospitals

Directional distribution of acoustic energy density incident to a surface under reverberant condition

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