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Aeroacoustic source measurement methods for characterizing the sound generated by ducted flow devices with higher-order modes.

Newman, TJ and Agarwal, A and Dowling, AP and Desvard, L (2013) Aeroacoustic source measurement methods for characterizing the sound generated by ducted flow devices with higher-order modes. J Acoust Soc Am, 134. 4099-.

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Abstract

The International Organization for Standardization (ISO) method 5136 is widely used in industry and academia to determine the sound power radiated into a duct by fans and other flow devices. The method involves placing the device at the center of a long cylindrical duct with anechoic terminations at each end to eliminate reflections. A single off-axis microphone is used on the inlet and outlet sides that can theoretically capture the plane-wave mode amplitudes but this does not provide enough information to fully account for higher-order modes. In this study, the "two-port" source model is formulated to include higher-order modes and applied for the first three modes. This requires six independent surface pressure measurements on each side or "port." The resulting experimental set-up is much shorter than the ISO rig and does not require anechoic terminations. An array of six external loudspeaker sources is used to characterize the passive part of the two-port model and the set-up provides a framework to account for transmission of higher-order modes through a fan. The relative importance of the higher-order modes has been considered and their effect on inaccuracies when using the ISO method to find source sound power has been analyzed.

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div A > Fluid Mechanics
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 12:03
Last Modified: 13 Oct 2014 01:17
DOI: 10.1121/1.4830975

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