Scattering investigation based on acoustical holography

Cheng, Ming-Te

doi:10.31274/rtd-180813-10024

Cited by 2 publications

(3 citation statements)

References 22 publications

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“…The results indicate that there is little sensitivity to the shift and axial translation. 2 The offset and skew, however, cause significant errors.…”

Section: B Cylindrical Coordinate Systemmentioning

confidence: 98%

Sensitivity of the wave-number domain field separation methods for scattering

Cheng

Mann

Pate

1996

The Journal of the Acoustical Society of America

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The two-surface field separation technique for obtaining the sound field scattered from an object has been shown to be feasible for both the Cartesian and cylindrical coordinate systems ͓Cheng et al., J. Acout. Soc. Am. 97, 2293-2303 ͑1995͔͒. Investigations of the sensitivity of implementing these separation techniques to the measurement parameters and their errors will be reported. The results of this sensitivity investigation are helpful in deciding the accuracy of the far-field target strength results and designing experimental procedures and equipment that ensure accurate results. The separation and the spatial processing parameters that are considered include the distance between measurement points in each measurement surface, the aperture size of each measurement surface, and the distance between measurement surfaces. Recommendations for these parameters are made. Next the sensitivity to errors in the experimental geometry is explored. For the Cartesian coordinate system skew and curvature of the measurement surfaces caused the most significant errors. For the cylindrical coordinate system errors in the measurement cylinder radii and skew caused the most significant errors. In both coordinate systems the errors could not be effectively corrected with signal processing except for the skew in the case of the cylindrical coordinate system.

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“…The results indicate that there is little sensitivity to the shift and axial translation. 2 The offset and skew, however, cause significant errors.…”

Section: B Cylindrical Coordinate Systemmentioning

confidence: 98%

Sensitivity of the wave-number domain field separation methods for scattering

Cheng

Mann

Pate

1996

The Journal of the Acoustical Society of America

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“…A system for making measurements with a single microphone is described by Cheng (Cheng 1993). In a single microphone system, a microphone is attached to a scanner to measure the sound pressure at the grid points of the measurement plane and a reference signal from the input to the amplifier that drives the sound sources is also measured.…”

Section: Single Microphone Data Collectionmentioning

confidence: 99%

“…Hz. Reflection of waves from the fiberglass wedges is reduced enough to achieve nearly free space conditions within the chamber (Cheng 1993).…”

Section: Single Microphone Data Collectionmentioning

confidence: 99%

Projecting nearfield acoustical holography (NAH) past intermediate sources

Zechmann¹

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With planar nearfield acoustic holography (NAH), the complex acoustic pressure and the three components of the acoustic velocity vector can be estimated on a plane near a complex source surface to identify individual noise sources. However, there are often intermediate sources between the measurement plane and the primary source plane. The NAH technique in its classical form cannot be extended past the intermediate source. A method will be presented to remove the intermediate sources, so that NAH can be extended to the surface of the primary source. The normal velocity at the surf ace of an intermediate source is used to estimate the complex pressure due to the intermediate source on the measurement plane, which is then subtracted from the measured data, providing an estimate of the measured sound pressure, if the intermediate source was not present. NAH is then used to project to the surface of the primary source. The source removal process was tested with simulated and measured data. Results for two methods to estimate the pressure caused by the intermediate source, inverse NAH and a point source approximation, will be presented. Also, a third method of source removal based on approximating the intermediate source as a force distribution function in the wave equation is also presented. The results show the effectiveness and limitations of the source removal process.

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Scattering investigation based on acoustical holography

Cited by 2 publications

References 22 publications

Sensitivity of the wave-number domain field separation methods for scattering

Sensitivity of the wave-number domain field separation methods for scattering

Projecting nearfield acoustical holography (NAH) past intermediate sources

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