METHODS FOR EVALUATING PERFORMANCE OF SMALL ACOUSTIC FILTERS

Experimental methods are needed for determining the characteristics of small acoustic filters used in systems with pulsating gas flows. These characteristics could then be used to predict the performance of proposed filter designs in a particular system, according to plane wave acoustic theory. Dependence on trial and error experimentation in solving noise control problems would thus be minimized. A literature survey revealed only a few earlier attempts to evaluate the acoustic performance of small filters and filter elements. Three methods for determining reflection and transmission factors are described, evaluated, and compared. A method employing a standing wave tube of unique design is recommended for determination of reflection factors. Transmission factors are obtained from reflection factors and pressure measurements at the filter inlet and outlet. Use of an anechoic termination simplifies the calculations and increases accuracy; design and evaluation of such a termination is described. © 1969, Acoustical Society of America. All rights reserved.