High-Frequency Sonar Performance
High-Frequency Sonar Performance
Active sonars that operate at frequencies above about 100 kHz are used in shallow water ocean environments to find objects located in the water column and on the ocean bottom. Sonar imaging capability improves at higher frequencies where wavelengths are smaller, but sonar detection range decreases due to increased sound absorption at higher frequencies. Additionally, sonar performance is limited by back-scattered sound from the ocean bottom, surface, and volume, as well as noise from wind and thermal effects. Sonar performance is measured in terms of the signal-to-noise ratio (SNR). High SNR corresponds to situations where the desirable target echo power exceeds the background reverberation and noise power. Sonar SNR is controlled by a variety of factors including the sonar source level, frequency, depth, tilt angle, and beam width. The sonar SNR is also influenced by target reflectivity, bottom type, and local wind conditions. This Demonstration shows those areas near the sonar where the SNR measured on a decibel scale is positive. Warmer colors correspond to higher SNR values.