Experimental evaluation of the aeroacoustic characteristics of a source of pulsating gas flow

Abstract

Among various methods, the transmission line or the impedance tube method has been most popular for the experimental evaluation of the acoustical impedance of a termination. The existing methods, including the ones reported earlier, by the authors require location of the sound pressure minima and/or maxima, or else make use of some iterative procedures. The present paper deals with a method of analysis of standing waves which does not depend on any of these involved procedures. It is applicable to the case of stationary as well as moving media. It enables on to evaluate the impedance of any passive black box, as well as the aeroacoustic characteristics of a source of pulsating gas flow, with the least experimental work and computation time and with the extra advantage of using a given impedance tube for wavelengths as large as four times its length. A method of external measurements, not involving use of any impedance tube, for evaluating the aeroacoustic characteristics of a source of pulsating gas flow is also dealt with, based on the definition of attenuation or insertion loss of a muffler.