抄録
An effective silencer of an air conditioning duct is studied. A duct with an acoustically soft boundary is employed as the effective silencer. On the acoustically soft boundary the sound pressure is zero and it is impossible to realize in the air-borne sound field, because of the non-existence of very much lighter medium than the air. In this study, an arrangement of one-quarter wave length acoustic tubes is employed as the soft boundary. This acoustic tube has frequency dependence, but sound pressure becomes nearly zero at the tube mouth around odd resonance frequency. Several numerical and experimental examples of duct silencers composed of acoustically soft boundaries are presented.
