WANG Zuomin LIN Lei JIANG Zaixiu

(Institute of Acoustics, Tongji University 200092 Shanghai)

Received Mar. 24, 2009

Revised Apr. 3, 2009

Abstract There are three effects of grazing mean flow on acoustical characteristics of the micro-perforated panel absorber (1) on radiation impedance of the orifice, (2) on acoustical impedance of the construction at sound wave angle incidence, (3) on sound propagation property in a duct lined by absorber. Based on the acoustical fundamental principle, these effects were analyzed respectively, and relative formulas were derived.Some qualitative tendencies were shown that radiation impedance of an orifice, value of ζ in function coth(ζ) which estimates cavity impedance, and transmission loss in a lined duct all will decrease with flow speed increases as well as the resonant frequency will move to lower frequency caused by Doppler Effect, when sound wave propagation direction is the same with flow direction.The discussion was also supported by a relative experimental study.

PACS numbers: 43.50