Determination of the Mutual Radiation Resistances of a Rectangular Plate and Their Impact on the Radiated Sound Power

Li, W.L.; Gibeling, H. J.

doi:10.1006/jsvi.1999.2592

Cited by 69 publications

(34 citation statements)

References 17 publications

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“…both odd or both even in each of the x and y directions. Li and Gibeling [67] have shown that the cross-modal coupling could have a significant impact on the radiated power, depending upon frequency and load condition. In particular it is found that the effect is significant between pairs of low order modes.…”

Section: Spatial Domain Approachmentioning

confidence: 99%

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Sound radiation from perforated plates

Putra

Thompson

2010

Journal of Sound and Vibration

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FACULTY OF ENGINEERING, SCIENCE AND MATHEMATICS INSTITUTE OF SOUND AND VIBRATION RESEARCH Doctor of Philosophy SOUND RADIATION FROM PERFORATED PLATES by Azma PutraPerforated plates are quite often used as a means of engineering noise control to reduce the sound radiated by structures. However, there appears to be a lack of representative models to determine the sound radiation from a perforated plate. The aim of this thesis is to develop such a model that can be used to give quantitative guidance corresponding to the design and effectiveness of this noise control measure.Following an assessment of various models for the radiation efficiency of an unbaffled plate, Laulagnet's model is implemented. Results are calculated and compared with those for baffled plates. From this, simple empirical formulae are developed and give a very good agreement with the analytical result. Laulagnet's model is then modified to include the effect of perforation in terms of a continuously distributed surface impedance to represent the holes. This produces a model for the sound radiation from a perforated unbaffled plate. It is found that the radiation efficiency reduces as the perforation ratio increases or as the hole size reduces. An approximate formula for the effect of perforation is proposed which shows a good agreement with the analytical calculation up to half the critical frequency. This could be used for an engineering application to predict the noise reduction due to perforation.The calculation for guided-guided boundary conditions shows that the radiation efficiency of an unbaffled plate is not sensitive to the edge conditions. It is also shown that perforation changes the plate bending stiffness and mass and hence increases the plate vibration.The situation is also considered in which a perforated unbaffled plate is located close to a reflecting rigid surface. This is established by modifying the Green's function in the perforated unbaffled model to include an imaginary source to represent the reflected sound. The result shows that the presence of the rigid surface reduces the radiation efficiency at low frequencies.The limitation of the assumption of a continuous acoustic impedance is investigated using a model of discrete sources. The perforated plate is discretised into elementary sources representing the plate and also the holes. It is found that the uniform surface impedance is only valid if the hole distance is less than an acoustic wavelength for a vibrating rectangular piston and less than half an acoustic wavelength for a rectangular plate in bending vibration. Otherwise, the array of holes is no longer effective to reduce the sound radiation.Experimental validation is conducted using a reciprocity technique. A good agreement is achieved between the measured results and the theoretical calculation for both the unbaffled perforated plate and the perforated plate near a rigid surface.

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Section: Spatial Domain Approachmentioning

confidence: 99%

“…One approach is to use series expansions. For a further description of this approach, one can refer to reference [66] or [67].…”

Section: Spatial Domain Approachmentioning

confidence: 99%

Sound radiation from perforated plates

Putra

Thompson

2010

Journal of Sound and Vibration

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“…(41)] is half of the e of Thomasson (1982). The first method for undertaking this reduction is presented in Appendix A of Li and Gibeling (2000) and Appendix 12.A of Allard and Atalla (2009). As Eq.…”

Section: Average Specific Radiation Impedancementioning

confidence: 99%

The average specific forced radiation wave impedance of a finite rectangular panel

Davy

Larner

Wareing

et al. 2014

The Journal of the Acoustical Society of America

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The average specific forced radiation wave impedance of a finite rectangular panel is of importance for the prediction of both sound insulation and sound absorption. In 1982, Thomasson published numerical calculations of the average specific forced radiation wave impedance of a square of side length 2e for wave number k in half octave steps of ke from 0.25 to 64. Thomasson's calculations were for the case when the forced bending wave number k b was less than or equal to k. Thomasson also published approximate formulas for values of ke above and below the published results. This paper combines Thomasson's high and low frequency formulas and compares this combined formula with Thomasson's numerical calculations. The real part of the approximate formula is between 0.7 dB higher and À1 dB lower than the numerical calculations. The imaginary part of the approximate formula is between 2.3 dB higher and À2.6 dB lower than the numerical calculations. This paper also gives approximate formulas for the case when k b is greater than or equal to k. The differences are between 0.8 and À1.2 dB for the imaginary part and between 6.2 and À2.4 dB for the real part.

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“…(15) is not well suited for numerical integration. Thus, a numerically more convenient expression with just two integrals, following the procedure described by Brunskog, 18 based on a variable substitution, 21 is given by…”

Section: Computation Of the Radiation Impedancementioning

confidence: 99%

In situ measurements of the oblique incidence sound absorption coefficient for finite sized absorbers

Ottink

Brunskog

Jeong

et al. 2016

The Journal of the Acoustical Society of America

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Absorption coefficients are mostly measured in reverberation rooms or with impedance tubes. Since these methods are only suitable for measuring the random incidence and the normal incidence absorption coefficient, there exists an increasing need for absorption coefficient measurement of finite absorbers at oblique incidence in situ. Due to the edge diffraction effect, oblique incidence methods considering an infinite sample fail to measure the absorption coefficient at large incidence angles of finite samples. This paper aims for the development of a measurement method that accounts for the finiteness of the absorber. A sound field model, which accounts for scattering from the finite absorber edges, assuming plane wave incidence is derived. A significant influence of the finiteness on the radiation impedance and the corresponding absorption coefficient is found. A finite surface method, which combines microphone array measurements over a finite sample with the sound field model in an inverse manner, is proposed. Besides, a temporal subtraction method, a microphone array method, impedance tube measurements, and an equivalent fluid model are used for validation. The finite surface method gives promising agreement with theory, especially at near grazing incidence. Thus, the finite surface method is proposed for further measurements at large incidence angles.

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Determination of the Mutual Radiation Resistances of a Rectangular Plate and Their Impact on the Radiated Sound Power

Cited by 69 publications

References 17 publications

Sound radiation from perforated plates

Sound radiation from perforated plates

The average specific forced radiation wave impedance of a finite rectangular panel

In situ measurements of the oblique incidence sound absorption coefficient for finite sized absorbers

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