Whereas there have been numerous theoretical and experimental studies on the properties of marine granular sands, there are significantly fewer studies on sediments classified as muds. The validity of geoacoustic models for muddy sediments has not been successfully tested due to the lack of inverted low-frequency sound speed and attenuation values. The geoacoustic properties of a surface fine-grained mud layer, overlaying three sand transition layers, and a half-space basement within the New England Mud Patch, were studied using explosive signals from long-range along-shelf sound propagation tracks. The sound-speed profile of the mud layer in the low-frequency band (100–500 Hz) was estimated using acoustic normal mode characteristics including the mode shapes and the modal dispersion curves of low-order modes, which mainly propagated in the water column and the surface mud layer. The ambiguity of sound speed at the top of the mud layer and sound-speed gradient was approximately removed. It was found that the resultant sound-speed ratio at the water-sediment interface was close to unity and the sound-speed gradient was 1.8 1/s with a standard deviation of 1.0 1/s. The attenuation in the mud layer was inverted using the attenuation coefficient of the first mode extracted from explosive signals at three source locations. The estimated attenuation at 150 Hz had a mean of 0.006 dB/m and a standard deviation of 0.003 dB/m.

中文翻译：

---

使用低阶模式估计地表泥层中的低频声速和衰减

尽管对海相颗粒砂的特性进行了大量的理论和实验研究，但对归类为泥浆的沉积物的研究却少之又少。由于缺乏倒置的低频声速和衰减值，泥质沉积物地声模型的有效性尚未得到成功测试。使用来自长距离沿搁板声传播轨道的爆炸信号研究了新英格兰泥块内覆盖三个砂过渡层的表面细粒泥层和半空间基底的地声特性。泥层在低频段 (100–500 Hz) 的声速剖面是使用声学法向模态特性估计的，包括低阶模态的模态形状和模态色散曲线，主要在水体和表层泥层中传播。近似消除了泥层顶部声速和声速梯度的模糊性。发现在水-沉积物界面合成的声速比接近于1，声速梯度为1.8 1/s，标准偏差为1.0 1/s。泥层中的衰减使用从三个源位置的爆炸信号中提取的第一模式的衰减系数进行反演。150 Hz 下的估计衰减平均值为 0.006 dB/m，标准偏差为 0.003 dB/m。发现在水-沉积物界面合成的声速比接近于1，声速梯度为1.8 1/s，标准偏差为1.0 1/s。泥层中的衰减使用从三个源位置的爆炸信号中提取的第一模式的衰减系数进行反演。150 Hz 下的估计衰减平均值为 0.006 dB/m，标准偏差为 0.003 dB/m。发现在水-沉积物界面合成的声速比接近于1，声速梯度为1.8 1/s，标准偏差为1.0 1/s。泥层中的衰减使用从三个源位置的爆炸信号中提取的第一模式的衰减系数进行反演。150 Hz 下的估计衰减平均值为 0.006 dB/m，标准偏差为 0.003 dB/m。