Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/24096
Title: Experimental study of sound propagation in a flexible duct
Authors: Huang, L
Choy, YS
So, RMC
Chong, TL
Issue Date: 2000
Publisher: Acoustical Society of America
Source: Journal of the Acoustical Society of America, 2000, v. 108, no. 2, p. 624-631 How to cite?
Journal: Journal of the Acoustical Society of America 
Abstract: Propagation of sound in a flexible duct is investigated both theoretically and experimentally. Strong coupling of sound and flexural waves on the duct wall is found when the wall-to-air mass ratio is of the order of unity. The axial phase speed of sound approaches the in vacuo speed of flexural waves (subsonic in this case) at low frequencies. However, a speed higher than the isentropic sound speed in free space (340 m/s) is found beyond a critical frequency which is a function of the mass ratio. Experiments using a duct with a finite section of tensioned membrane are compared with the propagating modes pertaining to the infinite membrane model. Satisfactory quantitative agreement is obtained and the measured phase speed ranges from 8.3 to 1348 m/s. In the moderate frequency range, the theory predicts high spatial damping rate for the subsonic waves, which is consistent with the experimental observation that subsonic waves become increasingly undetectable as the frequency increases. Substantial sound reflection is observed at the interface between the rigid and the flexible segments of the duct without cross-section discontinuity, which, together with the high spatial damping, could form a basis for passive control of low-frequency duct noise.
URI: http://hdl.handle.net/10397/24096
ISSN: 0001-4966
EISSN: 1520-8524
DOI: 10.1121/1.429594
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