Analysis of shallow water sound velocity profile impact on detection performance of active sonar signal

Range is the most important index of the detection performance of active sonar systems, and is influenced by the parameters of the sonar system, marine environment and target characteristics. The traditional method of predicting detection range was to solve the active sonar equation. Because parameters such as transmission loss and reverberation are computed as an average energy value, the result couldn't reflect the sea channel characteristics and had a larger error; actual experimental results had showed that the impact of sound velocity profile varied from signal form. In order to explore the association between sound velocity profile in shallow water, signal form and detection model, a model of point target echo waveform reflecting channel propagation properties and based on the system function of coherent multiplicity channels, was established. This was achieved by selecting the information such as time delay, amplitude attenuation and phase change carried by the major Eigen Ray, as solved by the theory of Ray Trace. Detecting the echo by use of the statistical signal detection theory, the parameters of the echo and detection model were corrected using the measured data, and the actual measured range was used as a reference value. For several different cases of sound velocity profiles in shallow water, the detection range of two kinds of ordinary active sonar signal was analyzed. Finally in relation to the reference range, the effect of the gradient and location upon a transducer array in a shallow water thermocline on the detection performance of the active sonar system was analyzed. The simulation results could provide a theoretical reference for the prediction of sonar performance according to the actual hydrological conditions. Thus rational advice can be provided for setting the depth of the transducer and selecting the transmitting signal form and detection methods in active sonar systems, and the foundation laid for further study of how complex hydrological conditions affect the detection performance of such systems.