Underwater acoustics — sound propagation in seawater (speed, absorption, spreading loss), sonar equation (SL-TL-NL+DI≥DT), passive and active sonar, transmission loss (spherical/cylindrical/ray tracing), transducer design (piezoelectric, BVD model, directivity, TVR/OCV), ambient noise (Wenz curves), target strength, sound speed profiles (SOFAR channel), and NATO/ISO standards for underwater acoustic systems.
