Measurement of sound transmission and signal gain in the complex Strait of Korea

South China Sea Internal Tide/Internal Waves— Impact on the Temporal Variability of Horizontal Array Gain at 276 Hz

“…17) of the array gain degradation than the longer aperture. Following Carey [9], the coherence lengths of the signals received by the 29 array for the smallest, average, and largest array-gain degradation were calculated to be about 85, 30, and 5.5 . The coherence length for the average array gain degradation is similar to the 30 estimates made by Carey [9].…”

“…The slopes for the best case (upper dashed and dotted curve) and worst case (lower dotted curve) are 0.00647 and 0.18 dB/wavelength, respectively. The asterisk is the arraygain degradation estimated for the Straits of Korea by Carey et al [9] for a similar acoustic wavelength and range. The averaged array-gain degradation observed in the South China Sea and the Carey measurement are comparable in magnitude.…”

“…A separate sudden decrease in array gain and spatial coherence occurs in the JD 125.93-126 time interval and is correlated with the arrival of internal waves at the source location. There also is a corresponding decrease in signal to noise due to the presence of a research vessel in the vicinity of the receiving [9] in the Straits of Korea is denoted by ( ).…”

“…The plot indicates that array lengths 400 and 70 and 25 will realize array gain for the best, average, and worst cast array-gain degradations measured. Following Carey [9], the measured array-gain degradation can be used to estimate coherence lengths. For an exponential spatial coherence function raised to the power, the spatial coherence works out to 85, 30, and 5.5 lambda for a 30-array.…”

Shallow-Water Propagation

“…• Ongoing research with Dr. William Carey concerns signal gain and coherence modeling in the Strait of Korea waveguide [18] and additional investigations of predictability of range averaged broadband propagation properties [19].…”