权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Diffraction in finite-amplitude focusing sound field and its application to acoustical imaging.

有限振幅聚焦声场中的衍射及其在声学成像中的应用。

基本信息

批准号：
61550283
负责人：
SHIGEMI Saito
金额：
$ 1.28万
依托单位：
Tokai University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1987
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61550283/
关键词：
Focusing Source Nonlinearity Parameter Nonlinear Acoustics 超音波顕微鏡

项目摘要

A sinusoidal sound wave emitted by a spherically focusing source distorts in waveforms with propagation toward the focus mainly due to the elastic nonlinearity of the medium, which can be described with the nonlinearity parameter. It was theoretically and experimentally proved that the largest part of the second harmonic component seen at the post focal region was generated in the focal region, because the secound harmonic components generated in the preand post-focal region cancel each other affected by the phase shift of the sound wave passing through the focus. Inserting a sample whose nonlinearity parameter differs from that of surrounding medium (water) into the focal region, the magnitude of the second harmonic component with the phase parameter of <pi>/2 radians seriously changes. This leads to the possibility to detect and visualize how the nonlinearity parameter of samples immersed in the focus differs from water. On the other hand, since the wavf propagation of a cylindrically focusing source does not suffer a similar phase shift the second harmonic component generated at eh focal region cannot be dominant in the post focal region. Therefore only the spherically focused sound may be appropriate for the present research project. Assuming a general case where the linear parameters (the ambient density, the sound speed, and the absorption coefficient) of the sample differed from those of surrounding medium as well as the nonlinearity parameter, the influence of the sample on the sound wave was theoretically and experimentally discussed. The result shows that the second harmonic component observed in the post focal region strongly depends on the linear acoustic parameters as well as on the nonlinerity parameter. However the method to estimate the nonlinearity parameter when both the density and sound speed are known has been shown. The realization of a gaussian focusing source will hoprfully make possible to visualize the nonlinerity parameter of the sample.

由球形聚焦源发射的正弦声波在向焦点传播时波形失真，主要是由于介质的弹性非线性，其可以用非线性参数来描述。从理论和实验上证明了在焦后区所见的二次谐波分量的最大部分是在焦区产生的，这是因为在焦前区和焦后区产生的二次谐波分量受到通过焦点的声波相移的影响而相互抵消。在焦区插入非线性参数与周围介质（水）不同的样品，相位参数为/2弧度的二次谐波分量的幅值<pi>发生严重变化。这导致的可能性，以检测和可视化的非线性参数的样品浸没在焦点不同于水。另一方面，由于圆柱形聚焦源的波的传播不遭受类似的相移，所以在焦区处产生的二次谐波分量在焦后区中不能占主导地位。因此，只有球形聚焦的声音可能适合于本研究项目。假设样品的线性参数（环境密度、声速和吸收系数）与周围介质的线性参数以及非线性参数不同，从理论和实验上讨论了样品对声波的影响。结果表明，在焦后区观测到的二次谐波分量不仅与非线性参量有关，而且与线性参量有很强的依赖关系。然而，当密度和声速都已知时，估计非线性参数的方法已经被示出。高斯聚焦光源的实现将有望使样品非线性参数的可视化成为可能。