沉积物中声速和衰减系数的宽带测量方法

海底沉积物作为海洋波导声传播的下边界普遍存在于大洋中,获知其特性对于准确的声传播和混响建模是十分必要的。为了能够快速而准确地测量沉积物中的声速和衰减系数,提出一种基于脉冲压缩技术的测量方法,对接收信号进行压缩来提取透射波,根据不同厚度样品的透射波来计算沉积物中的声速和衰减系数。该方法不仅可以克服实验过程中经常遇到的多途干扰,而且测量过程简单,可以同时获得测量频带内所有频点的声速和衰减系数,即实现了对声速和衰减系数的宽带测量。在实验室环境条件下,90~170kHz的测量频带内,测得沙样品中的声速为1710~1713m/s,衰减系数在56~70dB/m之间。通过窄带和宽带测量结果的比较可以看出,声速的宽带测量结果与窄带测量结果吻合得较好,而衰减系数在频带后半部分存在较大的起伏。 

A wide-band method for sound speed and attenuation measurement in sediments

Marine sediments exist universally as the lower boundary for sound propagation in ocean waveguides, and knowledge of the properties of sediments is important for accurate modeling of sound propagation and reverberation. In order to measure sound speed and attenuation in sediments fast and accurately, a method based on pulse compression technique is proposed, where transmission wave is extracted from the received compressing signal. The sound speed and attenuation were measured according to transmission wave through different thicknesses of samples. This method not only can overcome unavoidable multi-path disturbance in experiment, but also can easily obtain the sound speed and attenuation for different frequencies in measured frequency band at the same time. That is, wide-band measurement for sound speed and attenuation is realized. In laboratory environment, the measured sound speed in the sand sample is 1710~1713 m/s and the attenuation is 56~70 dB/m in the frequency range of 90~170 kHz. Through the comparison of narrow and wide-band results, it is found that the sound speed measured by wide-band method agrees well with that of narrow-band method, while the attenuation exhibits large fluctuation at the second half of measured frequency band.