抄録
An improved TSP (time-stretched pulse) method for measuring an oblique incidence absorption coefficient is proposed. The value of the absorption coefficient obtained by this method is equivalent to the value obtained by the TSP method, in which the reflected sound is extracted from the difference of the pulse arrival time, in high reproducibility and short measuring time. The proposed method can measure the oblique incidence absorption coefficient for a shallower angle than the TSP method. In this method the sound that comes directly from the speaker is measured separately in a free sound field. Therefore, there is no need to separate the arrival time between the direct sound and the reflected sound from the surface of the specimen. The validity of this method was ascertained by comparing the numerical solution of the boundary element method and the solution of theoretical analysis, even in the case of an incident angle shallower than 45 degrees for the official specimen size (4×5m).
