Measuring Sound Absorption: Considerations on the Measurement of the Active Acoustic Power

Kuipers, E.R.; Wijnant, Ysbrand H.; Boer, A. de

doi:10.3813/aaa.918699

Cited by 4 publications

(6 citation statements)

References 19 publications

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“…The microphones are spaced 20.0 mm in the x-and y-direction, and 23.1 mm in the z-direction. As reported in an earlier paper [14], some diffraction effects between 4 and 6 kHz were observed during a series of calibration measurements. The resulting phase-and amplitude errors at these frequencies can, particularly for poorly absorbing samples, result in noticeable inaccuracies in the sound absorption curve, as observed in the same paper.…”

Section: Methodssupporting

confidence: 75%

“…If we would use the finite difference (FD) approximation to determine the particle velocity for use in Eq. (14), see Fahy [19]:…”

Section: Theory Of the Lspw-methodsmentioning

confidence: 99%

“…The distinct dips in this curve at 2273 and 6080 Hz are related to a variation of the local sound absorption coefficient within a part of the area of the measurement surface. This variation is caused by local detachment of the foam from the adhesive tape, and was analyzed more in detail by the authors in [14].…”

Section: Sample 1: Sound Absorbing Foammentioning

confidence: 99%

“…It is in contrast to currently available methods which rely on measurements using a spatially fixed set-up, being more susceptible to local deviations in the acoustic field that may be caused by edge-diffracted waves or room reflections. Practical use of areaaveraging for measurements in a non-ideal acoustic field has firstly been reported by the authors [14]. In that paper, the LPW-method (Local Plane Wave method) [15,16,17,13] was used.…”

Section: Introductionmentioning

confidence: 99%

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Measuring oblique incidence sound absorption using a local plane wave assumption

Kuipers¹,

Wijnant²,

Boer³

2014

Acta Acustica united with Acustica

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SummaryIn this paper a method for the measurement of the oblique incidence sound absorption coefficient is presented. It is based on a local field assumption, in which the acoustic field is locally approximated by one incident-and one specularly reflected plane wave. The amplitudes of these waves can be determined with an unidirectional sound intensity probe. The local active-and incident acoustic intensity are straightforwardly obtained. The area-averaged sound absorption coefficient is calculated after spatial integration of these quantities over the surface area of interest. Alternatively, one may use a three-dimensional intensity probe. In that case, the determination of the amplitudes of the plane waves can be formulated as a least-squares problem. Measurements performed for a sound absorbing foam demonstrate that accurate results can be obtained, even under non-ideal acoustic conditions. Measurements carried out for a periodic absorber show that the method is accurate below the cuton frequency of scattering as long as the amplitude of the evanescent surface waves is significantly smaller than that of the specularly reflected wave. PACS no. 43.20El, 43.55Ev, 43.55Dt

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Section: Methodssupporting

confidence: 75%

“…If we would use the finite difference (FD) approximation to determine the particle velocity for use in Eq. (14), see Fahy [19]:…”

Section: Theory Of the Lspw-methodsmentioning

confidence: 99%

Section: Sample 1: Sound Absorbing Foammentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Measuring oblique incidence sound absorption using a local plane wave assumption

Kuipers¹,

Wijnant²,

Boer³

2014

Acta Acustica united with Acustica

Self Cite

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“…Formore information about the design, characteristics and implementation of this 8p-probe, the reader is referred to [18]. Furthermore, in [18,20] the measurement technique is validated for several sound hard and sound absorbing materials for normal and oblique incidence.…”

Section: Measurement Setup and Techniquesmentioning

confidence: 99%

Prediction of Sound Absorption of Stacked Granular Materials for Normal and Oblique Incident Sound Waves

Bezemer-Krijnen¹,

Wijnant²,

Boer³

2018

Acta Acustica united with Acustica

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Tire-road noise is aproblem in many(densely)populated areas. It can be significantly reduced by using porous asphalt concrete. Achallenge is to develop porous asphalt concrete, such that the most dominant frequencies in tire-road noise will be absorbed by the road surface. It is especially important to also reduce and absorb oblique incident sound waves, since tires radiate noise normal to the tire surface, which means oblique incident waveson the road surface. Predicting the behavior of porous asphalt concrete using models is complex, especially when non-local effects and scattering effects are included. The objective of this paper is to showamodeling approach to predict sound absorption for oblique incident wavesinthree-dimensional porous materials. Using this method, one is able to predict the sound absorption of porous road surfaces in the design phase. This modeling approach includes at wo-step approach in which first the viscothermal energy dissipation inside the pores between the rigid materials (stones)a re estimated and then, secondly,the non-local effects such as scattering on the st ones within the porous road surface are computed using afinite element model. The combination of both sound fields givest he total sound field in and above the three-dimensional porous material, which is used to determine the sound absorption coefficient. The analytical viscothermal and scattering solution are discussed in this paper and the modeling approach is validated with experiments using ab ox with stacked marbles for several angles of incidence.

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On the area-averaged effective sound absorption coefficient of porous materials excited by a monopole

Sgard,

Atalla,

Robin

et al. 2024

The Journal of the Acoustical Society of America

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The area-averaged effective sound absorption coefficient (SAC) of a rigid-backed homogeneous porous material subjected to a monopole excitation is calculated as the absorbed-to-incident sound power ratio. Using Allard's model to describe the sound propagation above the porous material, an analytical model for this power-based SAC is proposed and proves to give a good approximation of the sound absorption performance under monopole excitation of sufficiently large areas of material. The impact of factors on the power-based SAC, such as monopole height, material radial dimension used to calculate the sound powers, and material properties is discussed. The power-based SAC frequency-dependent behavior is analyzed through sound intensity field assessments at the material surface and is compared to normal incident plane wave and diffuse field SACs. The sound absorption behavior of sound absorbers under monopole excitation exhibits notable distinctions and peculiar results compared to those observed under plane wave and diffuse fields, particularly at low frequencies and for sources close to the material.

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Measuring Sound Absorption: Considerations on the Measurement of the Active Acoustic Power

Cited by 4 publications

References 19 publications

Measuring oblique incidence sound absorption using a local plane wave assumption

Measuring oblique incidence sound absorption using a local plane wave assumption

Prediction of Sound Absorption of Stacked Granular Materials for Normal and Oblique Incident Sound Waves

On the area-averaged effective sound absorption coefficient of porous materials excited by a monopole

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