Acoustic Measurements in Deep Water Using the Bathyscaphe Free

In the summer of 1957, a series of dives for scientific purposes was made by the Bathyscaphe in the Tyrrhenian Sea off the west coast of Italy. Dives were made to 1000 meters and 3000 meters depth. This paper presents the results of the Hudson Laboratories part of the program, which consisted of low‐frequency (10–400 cps) acoustic measurements of ambient noise and of propagation from a surface source. The noise spectra are observed as a function of depth and sea state and are found to be relatively independent of depth in zero sea state and to increase approximately linearly towards the surface in sea state 2, the rate of increase being greater for frequencies over 60 cps than below 60 cps. Vertical profiles of the sound field from a surface source were taken at ranges up to 7 miles from the source. The energy at 7 miles is found to be concentrated in the deep sound channel, while at 3 miles no such concentration is observed. Finally the use of the Bathyscaphe for acoustic work in general is evaluated. (This work was supported by the Office of Naval Research.)