关于浅海声参量阵的应用

Westervelt远场参量阵理论表明,差频声压正比于它的降频比的平方,但对于近场,特别是到场点的距离比参量阵阵长小得可以忽略不计,但比发射换能器的瑞利长度大的情况下,结果应有所不同。本文将作者之一的理论用之于这种情况,得到了浅海参量阵的设计公式,这个公式给出的参量声压不是正比于f/f₀的平方,而是正比于R₀。此外,本文还对Moffett和Mellen的参量阵理论模型作了近似分析,得到了相同的设计公式,水池实验结果支持了本文的理论分析。 关键词：

ON APPLICATIONS OF PARAMETRIC ACOUSTIC SOURCES TO SHALLOW WATER

As is shown by westervelt, the difference-frequency sound pressure of the parametric array in the far field is proportional to the second power of f/f₀, the downshift ratio of the frequency. However, a different result may occure in the near field, especially, when the distence to the field point is much less than the length of the parametric array, but larger than R₀, the Rayleigh length of the transducer. In this paper, our previous theory is applied to the case of shallow water and an expression for the parametric array design has been given. It is shown that the parametric pressure is proportional to Ro, instead of proportional to the length of the parametric array or to the second power of f/f₀. Futhermore, an analysis for Moffett and Mellen's theory is also made in this paper and on identical expression has been obtained. Finally, an experiment is carried out in a pool and the results obtained support the theory.