Errors when assuming locally reacting boundary condition in the estimation of the surface acoustic impedance

Dragonetti, Raffaele; Romano, Rosario Aniello

doi:10.1016/j.apacoust.2016.08.024

Cited by 13 publications

(4 citation statements)

References 20 publications

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“…The method will of course be sensitive to the complex surface impedance being rather constant across segments of the calculation mesh used for the least-squares estimation. Use of a single point source at short-to-medium distance will cause the surface impedance to vary across the surface (see for example reference [22]) and therefore require the use of a very small averaging area.…”

Section: Theorymentioning

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%

“…The errors introduced by that assumption in Eqs. (4) and (5) could be investigated numerically by use of the analytical spherical wave-front models applied in reference [22]. This has not been done, but could be a topic for a future investigation.…”

mentioning

confidence: 99%

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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show abstract

“…Dragonetti and Romano estimated errors in assuming the locally reacting boundary condition for porous materials. 29 The authors proved that the acoustic surface impedance depended on airflow resistivity, the type of wavefront impinging on its surface, the angle of wave incidence, and the thickness of the porous material.…”

Section: Limitations Due To Simulation Methodsmentioning

confidence: 99%

A combined sound field prediction method in small classrooms

Yang

Mak

2021

Building Services Engineering Research and Technology

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In this paper, a new combination method for sound field prediction is proposed. An optimization approach based on the genetic algorithm is employed for optimizing the transition frequency of the combined sound field prediction method in classrooms. The selected optimization approach can identify the optimal transition frequency so that the combined sound field prediction can obtain more efficient and accurate prediction results. The proposed combined sound field prediction method consists of a wave-based method and geometric acoustic methods that are separated by the transition frequency. In low frequency domain (below the transition frequency), the sound field is calculated by the finite element method (FEM), while a hybrid geometric acoustic method is employed in the high frequency domain (above the transition frequency). The proposed combined prediction models are validated by comparing them with previous results and experimental measurements. The optimization approach is illustrated by several examples and compared with traditional combination results. Compared to existed sound field prediction simulations in classrooms, the proposed combination methods take the sound field in low frequencies into account. The results demonstrate the effectiveness of the proposed model. Practical applications: This study proposes a combined sound field prediction method separated by transition frequency. A genetic algorithm optimization method is employed for searching the optimal transition frequency. The outcomes of this paper are essential for acoustical designs and acoustical environmental assessments.

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“…However, the assumption of admittance boundary conditions is not appropriate for some porous materials, such as those with a low flow resistivity, backed by an air cavity [9,10] and instead the nonlocal behavior must be considered in the simulations. This is usually described as an equivalent fluid model (EFM) [11].…”

Section: Introductionmentioning

confidence: 99%

Model order reduction of time-domain vibro-acoustic finite element simulations with non-locally reacting absorbers

Cai,

van Ophem,

Desmet

et al. 2023

Computer Methods in Applied Mechanics and Engineering

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Errors when assuming locally reacting boundary condition in the estimation of the surface acoustic impedance

Cited by 13 publications

References 20 publications

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

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

A combined sound field prediction method in small classrooms

Model order reduction of time-domain vibro-acoustic finite element simulations with non-locally reacting absorbers

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