球音源の近くにおかれた方形板による回折効果

概要

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Telephone transmitter is used near a mouth, Therefore an analysis of the surrounding field containing a sound source (human head) and the transmitter is necessary for design of such a electro-acoustic transducer. In this paper, the diffraction coefficient of a rigid rectangular plate near a spherical sound source has been computed to obtain the properties of a telephone transmitter of rectangular shape as shown in Fig. 4. The reason we have adopted a spherical sound source in this system is that this source can be regarded as a first approximation of human head. It is difficult to analyze the sound field in this system rigorously, and in particular the values of diffraction coefficient at the center of the plate are desired. Therefore the authors have calculated the diffraction coefficient at that point by using the Kirchhoff's approximation method and the procedure in a previous paper in case of α=β=π/2 (Fig. 5). An example is shown in Fig. 8 for a=10 cm, d=20 cm, θ_0=14. 5゜, b : c=4 : 3 and 4bc=31. 2 cm_2 (Fig. 5). Furthermore, using such parameters, the diffraction coefficient of a rectangular plate and that of a rigid circular plate of the same area is compared (Fig. 9). As a result, it is shown that the agreement of both values is acknowledged in difference by less than 0. 3 dB ; that is, it is possible to exchange a rectangular plate with a circular one.
社団法人日本音響学会の論文
1974-04-01