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Journal of the Acoustical Society of America

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Aug 2007

Volume 122, Issue 2, pp. 681-EL49

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Experimental investigation of an inversion technique for the determination of broadband duct mode amplitudes by the use of near-field sensor arrays

Fabrice O. Castres and Phillip F. Joseph

J. Acoust. Soc. Am. Volume 122, Issue 2, pp. 848-859 (2007); (12 pages) | Cited 4 times

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This paper is an experimental investigation of an inverse technique for deducing the amplitudes of the modes radiated from a turbofan engine, including schemes for stablizing the solution. The detection of broadband modes generated by a laboratory-scaled fan inlet is performed using a near-field array of microphones arranged in a geodesic geometry. This array geometry is shown to allow a robust and accurate modal inversion. The sound power radiated from the fan inlet and the coherence function between different modal amplitudes are also presented. The knowledge of such modal content is useful in helping to characterize the source mechanisms of fan broadband noise generation, for determining the most appropriate mode distribution model for duct liner predictions, and for making sound power measurements of the radiated sound field.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.20.Ye Measurement methods and instrumentation

Modeling of the roundabout noise impact

Rufin Makarewicz and Roman Golebiewski

J. Acoust. Soc. Am. Volume 122, Issue 2, pp. 860-868 (2007); (9 pages) | Cited 1 time

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A roundabout is a very popular tool used by town planners for carrying smooth and stationary road traffic flow. In this study it is shown that the replacement of a classical road intersection by a roundabout, under certain conditions, may produce a traffic noise decrease. These conditions are expressed in terms of the roundabout speed and the receiver location. The A-weighted sound exposure level is used to describe noise reduction.
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43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
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