Sound absorbing device for ultra-low frequency sound

摘要

An infrasound absorbing structure is simple in construction and is capable of effectively controlling infrasonic noises. The infrasound absorbing structure is applied to an engine test cell or an engine runup hangar to reduce infrasonic noises generate therein. The infrasound absorbing structure includes a porous layer facing an infrasound source, and a back wall disposed opposite to the porous layer so as to define a back air layer of a thickness between 2 and 10 m between the porous layer and the back wall. The porous layer has a surface density in the range of 0.5 to 10 kg/m².