Effect of sound-speed profile on differential time-delay estimation

The sensitivity of correlograms to various sound-speed profiles is being studied in order to estimate the impact of refracted multipath acoustic energy on differential time-delay estimation (TDE). To do this, we utilize the generic sonar model to compute the crosscorrelation function for an array of two separated receivers in realistic ocean environments. The effects of the obtained correlogram peaks that show the differential time delays were compared with those predicted when assuming isovelocity profiles. The influence of a signal source’s range and bearing, as well as the vertical separation of the receivers on the correlograms, is demonstrated for each environment considered. Our results indicate that TDE may be significantly influenced by the processing of highly refracted rays of many different types due to the selected sound-speed profile. Also, the Cramer–Rao lower bounds to the standard deviation of time-delay errors at various signal-to-noise ratios are compared with the results that were derived using the generic sonar model and found to be in close agreement.