The Reflectivity of Two Bottom Areas as Measured by Total Energy Reflection Coefficients

Abstract

In a paper presented at the 72nd meeting of the Acoustical Society of America, the author discussed the high variability in the peak amplitude bottom reflection coefficients obtained using pulsed CW signals over an abyssal plain area. These results led to an investigation into the use of a reflected-to-incident energy ratio as a more suitable description of bottom reflectivity. Ratios between the integral-square values of the bottom-reflected and direct-path signal envelopes were computed for 100 msec pulsed CW and 250-msec linear frequency modulated (LFM) signals. The frequencies were 1080 and 3700 Hz for the CW; the LFM bands were centered on these frequencies. Results indicate that the integral-square ratios, which are essentially energy ratios, are as variable as the peak reflection coefficients. The variability, expressed as the interval bounded by the mean plus and minus one sigma, is higher for the 3700-Hz data. For both frequencies and signal types, this variability often exceeds 4 dB over survey areas only a few miles in extent.