What is Measured in Sound Absorption Measurements

Sabine, Paul E.

doi:10.1121/1.1915742

Cited by 14 publications

(3 citation statements)

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“…Owing to the edge effect, the absorption coefficient measured in a reverberation room can be larger than 1 as the geometrical area is used in the calculation of the absorption coefficient. More information on the edge effect can be found in [22,23].…”

Section: Measurement In Reverberation Roommentioning

confidence: 99%

Oblique incidence sound absorption of parallel arrangement of multiple micro-perforated panel absorbers in a periodic pattern

Wang

Huang

Zhang

2014

Journal of Sound and Vibration

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The sound absorption performance of a micro-perforated panel (MPP) absorber array at oblique incidence and in diffuse field is investigated both numerically and experimentally. The basic module of the MPP absorber array consists of four parallel-arranged MPP absorbers with different cavity depths, and the whole MPP absorber array is created by arranging the basic modules in a periodically repeating pattern. A three-dimensional finite element model is used to simulate the acoustic properties of the MPP absorber array. Results show that the influence of incidence angle lies in two aspects. First, the parallel absorption mechanism breaks down at lower frequencies at oblique incidence than at normal incidence due to the non-compactness of the resonating MPP absorber, which becomes non-compact if the time delay of incident wave across it is comparable to or larger than π/2. Second, the equivalent acoustic impedance of the MPP varies with respect to incidence angle which in turn changes the sound absorption performance of the MPP absorber array. Influence of the azimuthal angle is insignificant. It is also found that even the normal incidence sound absorption of the MPP absorber array differs from that of the basic module tested in impedance tube. The measured sound absorption coefficients of a prototype specimen in reverberation room compare well with the numerical predictions. The extra sound absorption due to diffraction of sound at the free edges of test specimen is the most efficient around 500 Hz.

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Section: Measurement In Reverberation Roommentioning

confidence: 99%

Oblique incidence sound absorption of parallel arrangement of multiple micro-perforated panel absorbers in a periodic pattern

Wang

Huang

Zhang

2014

Journal of Sound and Vibration

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“…This phenomenon can be explained as follows: for a MPP absorber flush-mounted in an infinite baffle, the impedance discontinuity between the baffle and the MPP generates a so-called "edge effect." 24 This phenomenon brings increased energy from the surrounding baffle region into the border of the MPP, particularly at low frequencies. According to Eq.…”

Section: A Oblique Incidence On a Mpp Absorbermentioning

confidence: 99%

Absorption of oblique incidence sound by a finite micro-perforated panel absorber

Yang

Cheng²

2013

The Journal of the Acoustical Society of America

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In this paper, a theoretical model of a micro-perforated panel (MPP) backed by a finite cavity and flush-mounted in an infinite baffle is developed and its performance in terms of sound absorption is analyzed. The model allows an oblique incidence sound impinging upon the MPP absorber. The simplified Rayleigh integral method, thin plate theory and the acoustical impedance of the MPP are used to calculate the sound energy absorbed by the MPP's surface. Results show that the absorption coefficient of the absorber is a function of angle and frequency of the incident sound, and is controlled by the coupling between the MPP and the acoustical modes in the back cavity. In particular, grazing modes can be induced in the cavity by sound with an oblique angle of incidence, which may result in peak sound absorptions at the natural frequencies of the modes. The mechanism involved is used to explain the absorption properties of the MPP absorber for a diffuse incidence of sound.

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“…At some frequencies, PTF results give a sound absorption coefficient greater than one for our system. This behavior can be explained by the fact that the present system is a three-dimensional one, in which the "edge effect" [20][21][22][23][24] occurs. In the low frequency range, the diffraction phenomenon in the vicinity of the edge of the MPP results in an increase of the energy absorption coming from the neighborhood of the edges.…”

Section: Absorption Coefficientmentioning

confidence: 99%

Modeling of micro-perforated panels in a complex vibro-acoustic environment using patch transfer function approach

Maxit

Yang

et al. 2012

The Journal of the Acoustical Society of America

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A micro-perforated panel (MPP) with a backing cavity is a well known device for efficient noise absorption. This configuration has been thoroughly studied in the experimental conditions of an acoustic tube (Kundt tube), in which the MPP is excited by a normal incident plane wave in one dimension. In a more practical situation, the efficiency of MPP may be influenced by the vibro-acoustic behavior of the surrounding systems as well as excitation. To deal with this problem, a vibro-acoustic formulation based on the patch transfer functions (PTF) approach is proposed to model the behavior of a micro-perforated structure in a complex vibro-acoustic environment. PTF is a substructuring approach, which allows assembling different vibro-acoustic subsystems through coupled surfaces. Upon casting micro-perforations and the flexibility of the MPP under transfer function framework, the proposed PTF formulation provides explicit representation of the coupling between subsystems and facilitates physical interpretation. As an illustration example, application to a MPP with a backing cavity located in an infinite baffle is demonstrated. The proposed PTF formulation is finally validated through comparison with experimental measurements available in the literature.

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What is Measured in Sound Absorption Measurements

Cited by 14 publications

References 0 publications

Oblique incidence sound absorption of parallel arrangement of multiple micro-perforated panel absorbers in a periodic pattern

Oblique incidence sound absorption of parallel arrangement of multiple micro-perforated panel absorbers in a periodic pattern

Absorption of oblique incidence sound by a finite micro-perforated panel absorber

Modeling of micro-perforated panels in a complex vibro-acoustic environment using patch transfer function approach

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