Results 151 to 160 of about 1,225 (190)
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Hybrid near-field acoustic holography
The Journal of the Acoustical Society of America, 2003Hybrid near-field acoustical holography (NAH) is developed for reconstructing acoustic radiation from an arbitrary object in a cost-effective manner. This hybrid NAH is derived from a modified Helmholtz equation least squares (HELS) formula that expands the acoustic pressure in terms of outgoing and incoming waves.
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Regularization methods for near-field acoustical holography
The Journal of the Acoustical Society of America, 2001The reconstruction of the pressure and normal surface velocity provided by near-field acoustical holography (NAH) from pressure measurements made near a vibrating structure is a linear, ill-posed inverse problem due to the existence of strongly decaying, evanescentlike waves.
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Near-field acoustic holography of acoustic radiation from structures
The Journal of the Acoustical Society of America, 2012There are some difficulties for conventional Near-field Acoustic Holography (NAH) to analyze acoustic radiation from a large scale structure. To solve the problem, a method for NAH of large scale structures was presented. In the method, the normal velocities or sound pressure at a few points on the surface of the structure are measured by transducers ...
Rongfu Mao, Zhimin Chen, Haichao Zhu
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Interior near-field acoustic holography based on finite elements
The Journal of the Acoustical Society of America, 2019This paper deals with the mathematical framework of near-field acoustic holography based on finite elements in application to the acoustic response of a fluid within a closed cavity to the enclosure boundary conditions. The finite element method is an effective implementation of the modal approach for arbitrary geometries and provides advantages for ...
Steffen, Ungnad, Delf, Sachau
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A one-step patch near-field acoustical holography procedure
The Journal of the Acoustical Society of America, 2007When performing holography measurements over a limited area of a source, the hologram pressure typically remains finite at the edge of the measurement aperture. Patch near-field acoustical holography (NAH) has been developed specifically to mitigate the effects related to that windowing.
Moohyung, Lee, J Stuart, Bolton
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Near-field acoustical holography—interior problems
The Journal of the Acoustical Society of America, 1997Near-field acoustical holography (NAH) provides a practical solution to a challenging inverse problem: Calculation of the normal velocity on the surface of a vibrator from the pressure field measured in the acoustic near field of the vibrating surface.
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THEORY AND BOUNDARY ELEMENT METHODS FOR NEAR-FIELD ACOUSTIC HOLOGRAPHY
Journal of Computational Acoustics, 2005We consider the problem of recovering surface vibrations from acoustic pressure measurements taken in the interior or the exterior of a region. We give two formulations of the problem. One is based on a representation of the pressure as layer potentials and the other is based on approximation by a class of specific solutions to the Helmholtz equation.
Delillo, Thomas +2 more
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Applications of Near-field Acoustic Holography on Small Apertures
The Journal of the Acoustical Society of America, 2008Small, finite measurement apertures are a major impediment for accurate and fast application of near-field acoustic holography (NAH). In theory, FFT-based NAH methods are very powerful and acquire extremely fast inverse calculations of the sound field.
Rick Scholte +3 more
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Near-field acoustical holography in enclosed spaces
The Journal of the Acoustical Society of America, 2003In enclosed spaces, the locations of surfaces from which most of the noise radiation occurs can be difficult to determine in the presence of reverberation and contributions from other sources. By using microphones configured in an array that confirms to the surface of interest, it should be possible to map the acoustic field inside the enclosed space ...
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Near-field acoustic holography of cyclostationary sound fields
The Journal of the Acoustical Society of America, 2012The radiated sound field of rotating machinery or reciprocating machinery has a significant periodically time-variant nature. This is a kind of non-stationary sound field and called cyclostationary sound field. In the conventional planar near-field acoustic holography(PNAH), this kind of sound field is treated as stationary field, so the information ...
Zhimin Chen, Hongchun Chen, Haichao Zhu
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