A series of standard U. S. Navy explosive charges was dropped by an aircraft en route from Bermuda to Brazil, and recordings were made at various hydrophone locations of the missile impact locating system in the Atlantic. Data from the Bermuda station have yielded attenuation coefficients between 10 and 480 cps for deep‐sea propagation over a total pathlength of 2600 miles. The results are compared with the compilation made by Thorp [J. Acoust. Soc. Am. 38, 648–654 (1965)]. The data suggest a low‐frequency relaxation process as one of a number of possible attenuation processes of sound transmission in the deep sea.