Long‐range propagation of sound generated at the ice‐water boundary Free

In order to investigate long‐range spatial affects of high ambient‐noise levels generated at the ice‐water boundary by the interaction of ocean waves with sea ice [O. I. Diachok and R. S. Winokur, J. Acoust. Sec. Am. 55, 750–53 (1974)], coincident measurements of the spatial variability of ambient noise, transmission loss, and thermal structure were made along several 300‐NM open water tracks normal to the boundary. The measurements were made from two aircraft with sonobuoys and expendable bathythermographs deployed and monitored every 20 NM, and explosive signals, deployed every 4 NM from one aircraft. The signals were detected on modified sonobuoys, which were monitored from a second aircraft. The resultant transmission loss data were corrected for cylindrical spreading and the attenuation coefficient was computed for comparison with the rate of change of the ambient noise versus distance measurements. An analysis of the results indicates that the ice‐water boundary may be considered as a line source of sound and that the observed variations of ambient‐noise signals with range may be quantitatively related to the computed attenuation coefficient.