Measurement of Absorption Coefficient, Surface Admittance, Radiated Intensity and Absorbed Intensity on the Panels of a Vehicle Cabin using a Dual Layer Array with Integrated Position Measurement

Mørkholt, Jakob; Hald, Jørgen; Hardy, Pierre; Trentin, D.; Bach‐Andersen, Martin; Keith, Graeme

doi:10.4271/2009-01-2170

Cited by 3 publications

(2 citation statements)

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“…As mentioned already, the new impedance-based method uses the same type of double-layer array and the same SONAH holography algorithm for in-situ measurements as the energy-based method [15][16].…”

Section: Theorymentioning

confidence: 99%

“…Hald et al [15][16] presented a similar method of estimating material properties by making use of a small double-layer microphone array in combination with a so-called patch-holography method called Statistically Optimized Near-field Acoustical Holography (SONAH) [17][18]. SONAH avoids the use of spatial DFT and therefore does not produce any replicated aperture errors, allowing the use of quite small material samples and arrays.…”

Section: Introductionmentioning

confidence: 99%

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In-situ impedance and absorption coefficient measurements using a double-layer microphone array

Hald¹,

Song²,

Haddad³

et al. 2019

Applied Acoustics

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Acoustic impedance is typically measured using an impedance tube, which requires a material sample physically fitted to the tube. However, the impedance can vary greatly between the material mounted in the tube and the material located in a real environment, where the mounting conditions are likely to be different. Also, oblique incidence cannot be measured in an impedance tube. In this paper, we investigate the use of a double-layer microphone array for in-situ measurement of surface impedance and absorption coefficient. With the array positioned near the material surface, a source emits broad-band sound towards the array and the material. A measurement is taken, and the sound pressure and the surface-normal particle velocity at the material surface are calculated using Statistically Optimized Near-field Acoustical Holography (SONAH). From the surface pressure and velocity, the impedance across a selected area is calculated, and finally the absorption coefficient is calculated from the impedance. A set of tests has been performed on porous material samples in an anechoic chamber as well as in a fitted room. Different sample sizes and different sound incidence angles have been considered. The results show consistency between the measurements in the anechoic room and the ordinary room as well as good agreement with Miki's model up to large oblique incidence angles.

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Section: Theorymentioning

confidence: 99%