New measurements of interval compressional wave velocities were made in the first sediment layer using the sonobuoy technique during two expeditions in the Bay of Bengal, in the Andaman Sea, and over the Nicobar Fan and Sunda Trench. Sediment interval velocities from these areas were added to those previously reported, and revised diagrams and regression equations of instantaneous and mean velocity versus one-way travel time are furnished for four areas of the Bengal Fan, and for the Anadman Basin, Nicobar Fan, Sunda Trench. The velocity gradients directly below the sea floor were used to separate the Bengal Fan into four geoacoustic provinces. In the north and west the velocity gradients are 0.86 and 1.28 s-1, respectively, whereas in the central part of the fan the gradient is 1.87 s-1. These variations indicate lesser increases of velocity with depth in the sea floor in the north and west, and they are probably due to more rapid deposition, less consolidation, and less lithification near the riverine source areas of the sediments. The near-surface velocity gradients in the other areas are the Andaman Basin, 1.53 s-1, the Nicobar Fan 1.63 s-1, and the Sunda Trench, 1.41 s-1. The linear velocity gradients (from the sediment surface to a given travel time) in 17 areas of the Indian Ocean, Pacific area, Atlantic Ocean, and Gulf of Mexico were averaged at each 0.1 s from 0 to 0.5 s of one-way travel time. These averaged gradients ranged from 1.32 s-1 at t=0 to 0.76 s-1 at t=0.5 s. The regression equation for the velocity gradients a, in s-1, as a function of one-way travel time t, in seconds, is a=1.316-1.117t (for use from t=0 to 0.5 s). These average velocity gradients can be used with sediment surface velocities and one-way travel times (measured from reflection records) to compute sediment layer thickness in areas of turbidites lacking interval velocity measurements in the first sediment layer.