How to obtain the propagation constant, the calculation method of the sound absorption coefficient of the sound absorbing material, sound absorption coefficient evaluation device

摘要

To provide a simple and high accuracy propagation constant, how to obtain the propagation constant capable of obtaining the sound absorption rate, calculation method sound absorption coefficient, and the sound absorption rate evaluation device. Method for obtaining A propagation constant is irradiated from the sound wave generating source 4 disposed at one end of the measuring tube 3 extending along an axis Ac, the wave to the noise absorbing member 2 disposed on the other end and, using a plurality of microphones 5 disposed apart from each other in the axial Ac direction so as to be in contact with the sound absorbing material 2, a method of obtaining the propagation constants to obtain the propagation constant of the noise absorbing member 2, a plurality of microphones calculating a transfer function of the acoustic waves between 5 together, based on the value of the transfer function, and a plurality of microphones 5 separation dimension between, (1) by equation calculating a propagation constant of the noise absorbing member 2 ,including. [Number 1] Incidentally, L represents a distance between the said _{microphone, H12,} H ₁₃ represent respectively the transfer function. .FIELD 1