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在海洋声速垂直分布为负跃层时，它会对远处表面噪声的传播起“屏蔽”作用。也就是说，负跃层（或负梯度）下，到达全向接收器的声能主要是近处的表面噪声。在特定的海域我们作了多次实验，初步结果表明：频率在１６０ＨＺ到２ＫＨＺ范围内，跃层下噪声场的谱级低于跃层上２—４ｄＢ；在６３ＨＺ—２ＫＨＺ之间，负跃层时的谱级要低于等速层时５—１０ｄＢ。 实验还表明，该海区频率在２ＫＨＺ以上的高频，谱级随昼夜变化有明显的规律，估计是该海域生物群体发声的结果。
When the vertical distribution of ocean sound velocity is negative, it can “shield” the spread of distant surface noise. That is to say, in the negative layer (or negative gradient), the acoustic energy reaching the omnidirectional receiver is mainly the near surface noise. We have made many experiments in a specific sea area. The preliminary results show that the spectral level of the noise field below the thermocline is 2-4dB below the thermocline in the frequency range from 160HZ to 2KHZ. Between 63HZ and 2KHZ, the negative thermocline When the spectral level is lower than the constant velocity layer 5-10dB. Experiments also show that the frequency of the sea above 2KHZ high frequency, spectral level with the diurnal changes have obvious regularity, it is estimated that the sound of the marine biological community results.