Seabed Observations at the New England Mud Patch: Reflection and Scattering Measurements and Direct Geoacoustic Information

• Published in: IEEE journal of oceanic engineering Vol. 47; no. 3; pp. 578 - 593
• Main Authors: Holland, Charles W., Smith, Chad M., Lowe, Zackary, Dorminy, Jim
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-07-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic measurements; Acoustic properties; Incidence angle; Measuring instruments; Mud; Ocean floor; Pollution measurement; Receivers; Reflection; Scattering; Sea measurements; seafloor; Sediment; sediment acoustics; Sediments; Sonar equipment; Sound; Sound velocity; United Kingdom > UK
• ISSN: 0364-9059; 1558-1691
• DOI: 10.1109/JOE.2021.3070028

Seabed reflection and scattering measurements were conducted at the New England Mud Patch to better understand the acoustic properties of fine-grained (muddy) sediments. The measurement philosophy and the measurements themselves are summarized. In addition, geoacoustic information accessed directly from the data in the time and frequency domains is presented. The main result is the existence of an angle of intromission. This observation proves that the mud sound speed is less than that of the water and yields a sediment sound speed ratio 0.9865 with outer bounds {0.985 0.989}. Another result is the observation of strong scattered arrivals from within the mud volume at/near normal incidence but not at low grazing angles. These are likely due to anisotropic sediment heterogeneities with a large horizontal to vertical scale. Evidence is also presented for a highly heterogeneous mud-sand horizon with lateral variability down to scales of order meters. Finally, the reflection measurements successfully capture Bragg interference patterns. Their importance is their substantial geoacoustic information content, which can be accessed by several inversion methods.