Passive acoustics

Passive acoustics is the action of listening for sounds, often at specific frequencies or for purposes of specific analyses.

As applied to underwater acoustics, also termed hydroacoustics or sonar, passive acoustics can be used to listen for underwater explosions, earthquakes, volcanic eruptions, sounds produced by fish and other animals, vessel activity or aquatic detecting equipment (as in hydroacoustics to track fish).

Hydroacoustics
Sonar	Active acoustics Baffles (submarine) Bistatic sonar Echo sounding Fessenden oscillator GLORIA sidescan sonar Multibeam echosounder Passive acoustics Scientific echosounder Side-scan sonar Sonar beamforming Sonobuoy Surveillance Towed Array Sensor System Synthetic aperture sonar Towed array sonar Upward looking sonar
Ocean acoustics	Acoustic network Acoustic release Acoustic Doppler current profiler Acoustic seabed classification Acoustical oceanography Hydrophone Long baseline acoustic positioning system Ocean acoustic tomography Short baseline acoustic positioning system Sofar bomb SOFAR channel Sound speed gradient Sound velocity probe Ultra-short baseline Underwater acoustics Underwater acoustic communication Underwater acoustic positioning system
Acoustic ecology	Acoustic survey in fishing Acoustic tag Animal echolocation Beached whale Deep scattering layer Fishfinder Fisheries acoustics Hearing range of marine mammals Marine mammals and sonar Whale song
Related topics	Acoustic signature Bioacoustics Biophony Geophysical MASINT Hydrographic survey Noise map Soundscape