Characteristics of sound signals on a quasi-stationary track between the Josephine and Ampere Seamounts

Abstract

Experimental data are presented on the measurement of the cross-correlation coefficients and the differences in the arrival times (temporal spectra) of acoustic signals transmitted through a 210-km-long quasi-stationary track in the Atlantic Ocean. At the summit of the Josephine Seamount, a continuous pseudonoise signal was emitted in the one-third-octave band with a mean frequency of 630 Hz. The signal was received at the Ampere Seamount by a 40-m flexible vertical array with a directivity pattern in the form of a static fan of 32 lobes. The width of each lobe was ∼3°. At a signal-to-noise ratio of about 3 dB and with an incomplete resolution of multipath signals by the array, the correlation coefficients reached a value of 0.48. The rms fluctuations of the differences in the arrival times varied from 1.8 to 3.1 ms depending on the signal arrival angles. The factors responsible for the low correlation coefficients and the relatively high fluctuations of the arrival time differences are discussed. Apparently, one of the factors is the presence of short-period internal waves.