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A six sensor method for measuring acoustic properties in ducts.

Newman, TJ and Agarwal, A and Dowling, AP and Desvard, L and Stimpson, R (2013) A six sensor method for measuring acoustic properties in ducts. J Acoust Soc Am, 133. 3404-.

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Abstract

An accurate description of sound propagation in a duct is important to obtain the sound power radiating from a source in both near and far fields. A technique has been developed and applied to decompose higher-order modes of sound emitted into a duct. Traditional experiments and theory based on two-sensor methods are limited to the plane-wave contribution to the sound field at low frequency. Due to the increase in independent measurements required, a computational method has been developed to simulate sensitivities of real measurements (e.g., noise) and optimize the set-up. An experimental rig has been constructed to decompose the first two modes using six independent measurements from surface, flush-mounted microphones. Experiments were initially performed using a loudspeaker as the source for validation. Subsequently, the sound emitted by a mixed-flow fan has been investigated and compared to measurements made in accordance with the internationally standardized in-duct fan measurement method. This method utilizes large anechoic terminations and a procedure involving averaging over measurements in space and time to account for the contribution from higher-order modes. The new method does not require either of these added complications and gives detail about the underlying modal content of the emitted sound.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:28
Last Modified: 28 Jul 2014 01:08
DOI: 10.1121/1.4805933

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