日本音響学会誌
Online ISSN : 2432-2040
Print ISSN : 0369-4232
有限振幅音波の非線形ひずみ
鎌倉 友男池谷 和夫
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ジャーナル フリー

1976 年 32 巻 4 号 p. 253-258

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In order to obtain a large acoustic power, it is necessary to drive the diaphragm of the source finitely in accordance with a desired waveform. However, there is not always a linear relation between the motion of the diaphragm and a received signal in the field. In particular, the wave at a receiver distorts as the amplitude at the source is increased. This fact is attributed to the nonlinearity of air, which is neglected for small amplitudes. In this sense, it seems to be important to investigate the nonlinear distortion in the radiation field and, in addition, to derive some simple relation for its phenomenon, if exists. A previous paper indicated the following results for a spherical sound source : the distortion coefficient of sound pressure (the second harmonic sound pressure to the fundamental) is proportional to the velocity of the diaphragm and does not always increase even if sound pressure level is raised. The latter shows the complexity of nearfield distortion. Although some nearfield distortion is usually present, this study shows that farfield distortion, except close to the source, governs the distortion field with increase of the frequency. Then an approximate equation of the distortion coefficient for a source in a free field is derived in neglect of sound absorption. This equation is expressed by some parameters which characterize the sound field. Next, measurements are made in the radiation field of a horn loudspeaker. The results are in satisfactory agreement with the theoretical value.

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© 1976 一般社団法人 日本音響学会
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