抄録
This paper presents a method to estimate the attenuation of a band noise by a thick barrier. In this method, the attenuation is assumed to be effected by two factors, one is the effect of a virtual thin barrer placed on the receiving side of the barrier with the same height and the other is the effect of thickness (see Eq. (1)). The charts to estimate the attenuation by a thin barrier are discussed in Section 3, and the validity of Meakawa's chart is verified by Macdonald's solution (see Figs. 2(a) and 2(b)). A new chart based on Macdonald's solution is offered to estimate the attenuation by a thin barrier more accurately (see Fig. 3) and the accuracy of this chart is checked numerically (see Figs. 4 and 5). The effect of thickness is discussed in Section 4. The effect of thickness is defined by the difference of sound pressure level in the shadow zone resulting from the replacement of a thin barrier by a thick barrier. The effect of thickness for a pure tone _p[ET] varies periodically along the frequency axis (see dashed curve in Fig. 6). For a band noise, this effect of thickness must be averaged over the frequency range of the noise. Then, from the practical point of view, a simplified chart to estimate the effect of thickness is offered withe a reasonable approximation when the thickness of barrier is larger than half a wave-length (see Fig. 9). The validity of the method presented here is verified by experimental results (see Fig. 10).
