Abstract
Assuming a opening from diffused sound field has the nature as though it is a plane-like assembly of non directional point sources, I analized the sound intensity attenuation along the perpendicular centre line from circular and slit-like openings and then proved experimentaly the analized logical formulas of attenuation are resonable for practical use, and for all frequencies. Some of the important results of this investigation are; 1. Ratio of sound intensity from circular opening is log_e{1+(R/l)^2}. R: radius of circular opening from diffused field. l: distance of receiving point from the opening. 2. Ratio of sound intensity from slit-like opening is 1/l tan^<-1> b/<2l> b: length of slit when the length of slit is much larger than width of it. l: distance of receiving point from the opening. 3. Sound intensity from point source (for circular opening when R/l<0.25, for slit-like one when b/2l<1) attenuats by 1/l^2 law. But sound intensity from line source (for slit b/2l>3) attenuats by 1/l law and for plane source attenuation by distance of receiving point is very little.
