Abstract
In this paper, the electrical circuits equivalent to the porous sound-absorbing materials are discussed. The sound absorption characteristics calculated with an electric simulator are compared with the experimental data obtained with a standing wave tube. The results are summarized as follows: (1)Analogies between acoustical constants and electrical ones make it possible to derive the equivalent circuit as in the case of non-dissipative acoustic filters. There exists a similarity law concerning the size, acoustical constants of materials, and frequencies. (2)A geometrical mean of the input impedances of both T-and π-type approximate lumpedconstant circuit may come near to the input impedance of original distributed-constant circuit, so the sound absorption characteristics determined by an impedance mismatching can be calculaterd in the upper-frequency range without truncation error. (3)The calculation and experimrnt of a thick (or thin) glass wool layer show a satisfactory agreement. It will be easy to unveil the nature of sound-absorbing materials, assuming arbitrary values for acoustical constants. (4)The attenuation characteristic of absorbent-lined duct is also studied as an example of multi-dimentional acoustical systems.
