SISTEMA PARA MEDIR PÉRDIDA DE TRANSMISIÓN DE SILENCIADORES ACÚSTICOS EN UN TUBO CON TERMINACIÓN ABSORBENTE ACTIVA

Abstract

An experimental arrangement for measuring transmission loss of acoustical filters in a tube with active non-reflecting terminal is implemented. A loudspeaker is used as a secondary source to suppress the reflected wave by means of a opposite phase radiation. Primary and secondary sources are fed with pure tones which excite only plane waves. The signals for the primary and secondary sources are generated by a computer, at the same time the computer calculates the current reflection coefficient from the microphone signals. The amplitude and phase of secondary signal are changed by means of an iterative method until a minimal reflection coefficient result. The experimental arrangement is tested by measurements on simple silencers (expansion chambers).