Knowra Passive acoustic monitoring Passive acoustic monitoring Passive acoustic monitoring uses underwater microphones, or hydrophones, to detect and study sounds without capturing animals. It can reveal animal presence, behavior, and changes in underwater soundscapes.
Hydrophone : A hydrophone is a sensor that converts underwater sound pressure into an electrical signal. It is the underwater microphone that captures sounds for passive monitoring.
Cetacean acoustics : Cetacean acoustics studies sound production, hearing, and communication in whales, dolphins, and porpoises. Many cetaceans produce calls detectable across long distances underwater.
Sound pressure level : Sound pressure level expresses the magnitude of sound pressure relative to a stated reference pressure, usually on a logarithmic scale. It provides a standard way to quantify recorded underwater sound intensity.
Active sonar : Active sonar emits sound pulses and analyzes their echoes to detect or locate objects underwater. Unlike passive monitoring, it creates sound rather than only listening.
Underwater acoustics : Underwater acoustics studies how sound is produced, transmitted, and received in water. Sound propagation determines which calls a monitoring station can detect.
Marine mammal monitoring : Marine mammal monitoring tracks animals and their presence, behavior, or population trends. Passive recordings can document animals that visual surveys miss.
Decibel : A decibel is a logarithmic unit expressing a ratio of power, intensity, or field quantities. Underwater recordings use decibel scales with explicitly stated reference pressures.
Visual survey : A visual survey records organisms or features observed directly by human observers or cameras. Visual surveys depend on visibility and surfacing, while acoustic monitoring can operate continuously underwater.
Acoustic localization : Acoustic localization estimates a sound source’s position from signals recorded by one or more sensors. Timing and level differences across hydrophones can locate calling animals.
Fish bioacoustics : Fish bioacoustics studies sounds produced and perceived by fishes. Some fishes call during courtship, territorial defense, or group activity.
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