干渉縞による平坦でない表面からの音響反射測定

抄録

In previous works, Y. Ando, Electron. Commun. (Japan)51, 10-18(1968) and Y. Ando, J. Acoust. Soc. Amer. , 45, 1563(L) (1969), the complex reflection coefficients from even surfaces were accurately measured by this method, considering the directivity and acoustic center of the transducers and excluding sphericity errors and the effect of diffraction by finite dimensions of the test materials. The reflection of sound from both even-and uneven walls has been a problem of interest in architectural acoustics. For example, to simulate the acoustic field of a rooms by computer before construction. It is evident that the method is also useful in the scatterd field near the boundary under certain conditions (see Fig. 2, and Eqs. (4) and (5)). Measurements were taken on a semicylindrical boss on a rigid plane (Fig. 3 and Fig. 5), a periodically uneven surface of rectangular profile (Fig. 6 and Fig. 8), and a louver array obliquely pleced on an absorbing material (Fig. 9 and Fig. 10). Tests were made considering a function of distance from reflecting point and angle of incidence (Fig. 1). The experimental values of the first two cases were compared with the calculated values. They agreed satisfactory in the lower frequency range. In the last case, it was found that experimental values were greatly dependent on the positive or negative sign of the incident angle, although no theoretical analysis has been attempted.