近海面水层中声传播损失估计和分析

近海面水层通常存在声速梯度变化,并随着季节的更替而改变。根据南海典型中等深度海在春季、夏季、秋季和冬季的声速剖面,分析近海面水层中12 km水平距离内声传播损失的空间分布和频率变化规律。结果表明:春、夏两季由于负梯度声影区现象,声传播损失约在1 km的距离超过80 d B;秋、冬两季的典型特征是存在表面声道现象,当声源在近海面混合层内部时,混合层中声传播损失在截止频率以上小于球面扩展损失,而当声源深度大于混合层深度时,表面声道现象不明显。

Estimation and analysis of acoustic propagation loss in the water layer near sea surface

The sound speed gradient usually varies with seasonal change in the water layer near sea surface. The acoustic propagation losses in the near surface layer are estimated for the different sound velocity profiles in typical mid-depth sea areas of the South China Sea in spring, summer, autumn and winter respectively. The characteristics of acoustic propagation losses for different types of sound speed profiles in the spatial and frequency domains are analyzed when the horizontal distance between the source and receiver is within 12km. The results show that, due to the negative gradient phenomenon which results in acoustic shadow zone, the acoustic propagation losses in the spring and the summer reach 80dB at the horizontal distance about 1km. While in the autumn and the winter, it is typical that the surface channel phenomenon exists, so the acoustic propagation loss is less than the spherical expansion loss at the frequency above the cutoff frequency when the source is located in the mixed layer near the sea surface. However, the surface channel phenomenon is not obvious when the source depth is greater than that of the mixed layer.