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1
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Total Acoustic Power of Two Concentric Clamped Circular Plates Vibrating in a Fluid

100%
Rdzanek W.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 1A
A-41-A-45
EN
This study focuses on the problem of sound radiation by two concentric clamped flat plates, circular and annular, into the half-space. The system of three coupled differential equations comprising two equations of motions of plates and the wave equation, is solved exactly. Vibrations of plates are axisymmetric and time-harmonic with a single excitation frequency. The initial phase difference of excitations can be nonzero. Attenuation due to fluid loading and material damping is included. Kirchoff-Love and Kelvin-Voigt theories are applied. The effect of initial phase difference of excitations on the acoustic power radiated is examined as well as errors resulting from neglecting the fluid loading.
2
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Asymptotic Formulae of the Modal Acoustic Impedance for the Asymmetric Vibrations of a Clamped Circular Plate

71%
Rdzanek W., Rdzanek W., Szemela K.
Acta Physica Polonica A
|
2010
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vol. 118
|
issue 1
141-154
EN
The asymptotic and approximate formulae for the asymmetric modal acoustic self- and mutual-impedance have been presented for a clamped circular plate embedded into a flat rigid baffle. The formulae have been obtained for the wide frequency band covering the low frequencies, the high frequencies and the middle frequencies. The high frequency asymptotics have been achieved using the method of contour integral and the method of stationary phase. The products of the Bessel and Neumann functions have been expressed as the asymptotic expansions. Further, the approximate formulae valid within the low and middle frequencies have been obtained from the high frequency asymptotics using some mathematical manipulations. The formulae presented are valid for both the axisymmetric vibrations and the asymmetric vibrations.
3
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The Acoustic Pressure Radiated by a Vibrating Circular Plate within the Fraunhofer Zone of the Three-Wall Corner Region

71%
Szemela K., Rdzanek W., Rdzanek W.
Acta Physica Polonica A
|
2012
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vol. 121
|
issue 1A
A-100-A-109
EN
The Neumann boundary value problem has been solved for the region bounded by the three perfect rigid infinite baffles arranged perpendicularly to one another. The harmonically vibrating clamped circular plate embedded in one of the baffles is the sound source. It has been assumed that the amplitude of the plate's transverse vibrations is small to use the linear Kelvin-Voigt theory. The Green function has been applied to obtain the asymptotic formulae describing the distribution of the acoustic pressure within the Fraunhofer zone. The analysis of sound radiation has been performed for some selected surface excitations and for some different plate's locations. The acoustic pressure distribution has been examined including the acoustic attenuation and the internal attenuation of the plate's material.
4
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Acoustic Impedance of an Annular Piston Wobbling in a Flat Screen Around a Semi-infinite Circular Cylinder

71%
Pieczonka D., Rdzanek W., Rdzanek W.
Acta Physica Polonica A
|
2013
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vol. 123
|
issue 6
1078-1084
EN
A rigorous solution is presented for the problem of sound radiation by an oscillating and wobbling annular piston embedded concentrically in a perpendicular flat screen surrounding a semi-infinite circular cylindrical baffle. Two forms of the Green's function of the considered region are used. The acoustic impedance is presented in its integral form useful for numerical calculations which enable studying the effect of the acoustic waves scattering on the cylindrical baffle and the asymmetry of vibration velocity on the piston on the resultant acoustic impedance of the wobbling piston. It is shown that in the case of the vibrating piston under consideration, the reciprocity of acoustic impedance related to two modes of rigid body motion, oscillating and wobbling, does not occur.
5
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The Low Frequency Approximation of the Sound Radiation Power of Two Vibrating Circular Pistons Embedded in Two Different Rigid Planes of a Three-wall Corner

71%
Rdzanek W., Rdzanek W., Szemela K.
Acta Physica Polonica A
|
2014
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vol. 125
|
issue 4A
A-135-A-143
EN
The problem of sound radiation by a system consisting of two vibrating circular pistons embedded in two of three different planes perpendicular to one another forming a three-wall corner is considered. The earlier published results dealing with the sound radiation by sources vibrating in a three-wall corner are the basis of analysis. According to the earlier studies, the exact formulae for acoustic power of radiation of two circular pistons are used. The formulae are expressed as double Fourier integrals. The active and reactive, self and mutual, components are separated from them as well as the corresponding expressions of the acoustic power of mirror images of the piston sources. The acoustic power of the two sources are expressed in the form of the Rayleigh formulae whereas, in the case of the mirror images, it is expressed in the form of the single series expansion containing spherical Bessel and Neumann functions. In the case of the mutual acoustic power of the sources, approximate formulae are presented for low frequencies. On the basis of the results obtained, the corresponding formulae valid for a two-wall corner are presented as the limiting transitions. All the results presented can be useful, e.g. in designing the room acoustics and outdoor system everywhere the free field conditions are disturbed by the acoustic waves reflected at rigid vertical walls for the wavelengths being considerably shorter than the geometric sizes of the walls.
6
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The Total Acoustic Power of a Clamped Circular Plate Located at the Boundary of Three-Wall Corner Region

51%
Szemela K., Rdzanek W., Pieczonka D.
Acta Physica Polonica A
|
2011
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vol. 119
|
issue 6A
1050-1060
EN
The energetic aspect of the sound radiation has been analyzed in the case of the three-wall corner region. This region is the part of space bounded by three baffles arranged perpendicularly to one another. The Neumann boundary value problem has been solved assuming that the sound source is the vibrating circular plate embedded in one of the baffles of the three-wall corner region. The Kelvin-Voigt theory of a visco-elastic plate has been used which allows to include internal attenuation existing in the plate material. It has been assumed that the sound source is excited to vibrations by the external pressure asymmetrically distributed on the plate surface. The modal coefficients of the acoustic impedance have been obtained in the form of the expressions containing single integrals only. The formula describing the acoustic power of the analyzed sound source has been presented as a fourfold infinite series containing the modal coefficients of the acoustic impedance. The influence of some asymmetric excitations on the acoustic power has been analyzed. The possibilities of the modelling some uniform excitations located on the plate fragment of the small area by the point force excitation has been examined. The influence of the transverse baffles on the acoustic power has also been investigated. It has been determined for which frequency the baffles influence on the acoustic power is the greatest.
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