Sound Speed Gradients in Mud

Various methods have been used to estimate sound speed profiles in mud at the New England Mud Patch. Some of these methods show large sound speed gradients of order 10 s−1. New measurements of the seabed reflection coefficient exhibit an angle of intromission over three octaves in frequency; these data constrain the range of possible sound speed gradient values. The data indicate that sound speed gradients must be quite weak, i.e., much smaller than |10 s−1|. This conclusion is supported by core data which indicate nearly constant porosity in most of the mud layer