Power Variances and Decay Curvature in a Reverberant System

Lobkis, Oleg I.; Weaver, Richard L.; Rozhkov, Igor

doi:10.1006/jsvi.2000.3057

Cited by 41 publications

(37 citation statements)

References 30 publications

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“…Other authors have also found values of K Ͻ 3, and in some cases it has been postulated that this could be due to the fact that the mode shapes are complex for nonproportionally damped systems ͓for example, Lobkis et al ͑2000͔͒. In both Langley and Brown ͑2004a, b͒ and the present work, proportional damping is considered and thus a value of K Ͻ 3 cannot be explained by the occurrence of complex modes, since the modes are purely real.…”

Section: Goe Natural Frequency Statisticsmentioning

confidence: 69%

“…͑25͒ requires knowledge of the statistical properties of the mode shapes. It is often postulated that the mode shapes associated with the GOE are Gaussian ͑Mehta, 1991͒, although a number of studies have revealed slight variations from Gaussian statistics for practical systems ͑Langley and Brown, 2004a, b; Weaver, 1989; Burkhardt and Weaver, 1996;Lobkis et al, 2000͒. This issue is discussed further in Sec.…”

Section: ͑17͒mentioning

confidence: 96%

“…An exception to the GOE occurs when the system has many symmetries, so that distinct groups of modes occur with no coupling between these groups, in which case Poisson natural frequencies can be expected ͑Mehta, 1991͒. The GOE has been used to study the steady-state response of a single subsystem by Langley and Brown ͑2004a, b͒, Weaver ͑1989͒, Weaver ͑1996͒, andLobkis et al ͑2000͒, and general built-up systems by Langley and Cotoni ͑2004͒. In contrast, the steady-state response of a single subsystem with Poisson statistics has been studied by Lyon ͑1969͒ and Davy ͑1981͒, and a Poisson-based analysis has been applied to built-up systems by Lyon and DeJong ͑1995͒.…”

Section: Introductionmentioning

confidence: 99%

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The ensemble statistics of the vibrational energy density of a random system subjected to single point harmonic excitation

Langley

Cotoni²

2005

The Journal of the Acoustical Society of America

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This paper is concerned with the ensemble statistics of the energy density of a random system subjected to a harmonic point load. Both the mean and variance of the reverberant energy density ͑i.e., the total response minus the direct field͒ are investigated. It is shown that the ensemble average of the reverberant energy density is not spatially homogeneous, but rather the value at the drive point is between two and three times the spatially averaged value, depending on the modal overlap factor. This result is closely analogous to established results regarding the case of transient excitation. Expressions are also derived for the relative variance of the reverberant energy density both remote from the drive point and at the drive point, and a number of anomalies are found in existing results. A comparison is made with simulation results for a randomized plate, and this comparison highlights the importance of the ensemble size considered in the simulations. The present analysis is based on a random point process model of the system natural frequencies, and both Gaussian orthogonal ensemble ͑GOE͒ statistics and Poisson statistics are considered.

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Section: Goe Natural Frequency Statisticsmentioning

confidence: 69%

Section: ͑17͒mentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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The ensemble statistics of the vibrational energy density of a random system subjected to single point harmonic excitation

Langley

Cotoni²

2005

The Journal of the Acoustical Society of America

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“…6 This seems to be generally accepted now. 7 A value of K = 3 has also been favored by Lobkis et al 8 In 1990, Davy 9 modified his theory so as to take account of the Gaussian orthogonal ensemble modal frequency spacing. Equation ͑3͒ now became…”

Section: ͑3͒mentioning

confidence: 99%

Sound power emitted by a pure-tone source in a reverberation room

Jacobsen

Molares

2009

The Journal of the Acoustical Society of America

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Energy considerations are of enormous practical importance in acoustics. In “energy acoustics,” sources of noise are described in terms of the sound power they emit, the underlying assumption being that this property is independent of the particular environment where the sources are placed. However, it is well known that the sound power output of a source emitting a pure tone or a narrow band of noise actually varies significantly with its position in a reverberation room at low frequencies, and even larger variations occur between different rooms. The resulting substantial uncertainty in measurements of sound power as well as in predictions based on knowledge of sound power is one of the fundamental limitations of energy acoustics. The existing theory for this phenomenon is fairly complicated and has only been validated rather indirectly. This paper describes a far simpler theory and demonstrates that it gives predictions in excellent agreement with the established theory. The results are confirmed by experimental results as well as finite element calculations.

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“…Efu n u n n 0 g=Ef9u n 9 2 g ¼ d nn 0 . The diffuse field normalized spatial correlation function C xx,diffuse ðx 1 ,x 2 ,oÞ is thus given by [21] …”

Section: Diffuse Field Correlation Functionmentioning

confidence: 99%