Non-invasive measurement of sound velocity profiles
Non-invasive measurement of sound velocity profiles
复制标题
声速剖面的非侵入式测量
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
M. Bock
中科院分区：
文献类型：
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作者：
E. Kühnicke;M. Lenz;M. Bock
在超声波中，到达物体界面的飞行时间通常是唯一需要考虑的信息。如果已知另一个值，则可以根据此信息确定距离或声速。声速和散射粒子到换能器的距离的组合确定使得可以测量声速分布。为了同时确定距离和声速，我们使用焦点位置作为超声波飞行时间之外的第二条信息。可以确定焦点位置，因为当散射粒子位于声场最大值内时，回声最强。因此，平均回波信号幅度的位置指示了到达焦点的时间。在之前使用带有透镜的强聚焦传感器进行的测量中，这种方法的准确度达到了 99.9%。当前的演示涉及测量声速剖面的第一步。为了测量速度分布，焦点位置，i。 e.声场最大值与换能器的距离通过环形阵列的波束形成而变化。通过使用适当的校准曲线，沿着声轴的不同点上的声速可以根据用于聚焦的所选择的时间滞后组和对应于平均回声信号幅度的最大值的飞行时间来确定。对具有恒定声速的介质中的局部分辨声速进行测量可产生有关不同焦距可达到的精度的信息。
In ultrasonics, the time of flight to the object interfaces is often the only information that is considered. From this information, one can either determine distances or sound velocities if the other value is known. A combined determination of the sound velocity and the distance of the scattering particles to the transducer makes it possible to measure sound velocity profiles. To determine distance and sound velocity simultaneously, we use the focus position as a second piece of information beside the ultrasonic time of flight. The focus position can be determined, because the echo becomes strongest when the scattering particle is located within the maximum of the sound field. Thus the position of the averaged echo signal amplitude indicates the time of flight to the focus. In previous measurements with a strongly focusing transducer with lens an accuracy of 99.9% was achieved with this method. The current presentation deals with first steps toward the measurement of sound velocity profiles. To measure a velocity profile, the focus position, i. e. the distance of the sound field maximum from the transducer, is varied by beam forming with an annular array. By using adequate calibration curves, the sound velocity on different points along the acoustic axis can be determined in dependence of the chosen set of time lags used for focusing and the time of flight corresponding to the maximum of the averaged echo signal amplitude. The measurement of the locally resolved sound velocity in media with constant sound velocity yields information about the accuracy that can be reached for varying focus distances.