The Seabed Characterization Experiment was carried out from March 5 to April 10, 2017 (SBCEX17) on the New England Mud Patch, approximately 90 km south of Martha's Vineyard. The SBCEX17 experimental site covers an area of 11 km × 30 km with water depth in the range of 75–80 m. The Sediment Acoustic-speed Measurement System (SAMS) is designed to measure sediment sound speed and attenuation simultaneously over the surficial 3 m of sediments. During SBCEX17, SAMS was successfully deployed at 18 sites, which were chosen to coincide with coring locations, with the goal of developing a geoacoustic model for the study area. In this article, a summary of SAMS operation during SBCEX17 is presented, as well as preliminary results for sediment sound speed and its spatial variation in the frequency band of 2–10 kHz. It is found that in mud, the sound-speed ratio is in the range of 0.98–1. Little dispersion was observed in this frequency band. Using the preliminary SAMS sound-speed results measured at different depths, the sound-speed gradient in mud within the surficial 3 m favors an exponential rather than a linear dependence at SBCEX17 site. Large gradients are observed for depth shallower than 1.5 m. For the sandy basement beneath the mud layer, the sound-speed ratio is as high as 1.105.

中文翻译：

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海底表征实验中细粒沉积物声速的测量

海底表征实验于 2017 年 3 月 5 日至 4 月 10 日（SBCEX17）在新英格兰泥滩上进行，距离玛莎葡萄园岛约 90 公里。SBCEX17 试验场面积 11 km×30 km，水深 75～80 m。沉积物声速测量系统 (SAMS) 旨在同时测量沉积物表面 3 m 上的沉积物声速和衰减。在 SBCEX17 期间，SAMS 成功部署在 18 个站点，这些站点被选择与取芯位置重合，目的是为研究区域开发地声模型。在本文中，介绍了 SBCEX17 期间 SAMS 操作的摘要，以及沉积物声速及其在 2-10 kHz 频带内的空间变化的初步结果。发现在泥里，声速比在0.98-1范围内。在该频带中观察到很少的色散。使用在不同深度测量的初步 SAMS 声速结果，表层 3 m 内泥浆的声速梯度有利于 SBCEX17 站点的指数而不是线性相关性。对于小于 1.5 m 的深度，观察到大梯度。对于泥层下的砂质基底，声速比高达1.105。