Hydrophone and Towed Arrays
|A hydrophone array consists of multiple hydrophones positioned in precise locations. The hydrophones and associated pre-amplifier boards are encased in an acoustically transparent, oil-filled tube. Arrays utilized by the Scripps Whale Acoustics Lab range from 100 – 300 meters in length and contain four to six individual hydrophones. The hydrophones utilized in our arrays have a frequency range extending from 10 Hz – 200 kHz, which permits recordings from a wide range of marine mammal species. Hydrophone arrays can either be towed behind a vessel for real-time, underway monitoring or fixed for stationary monitoring of a specific location. Sound arriving at the array from a source, such as a vocalizing whale, will reach each hydrophone at slightly different times. The time-of-arrival-differences can subsequently be used to calculate the bearing and distance to a calling animal. Hydrophone arrays are often used in association with visual observation techniques to allow for marine mammal calls to be correlated with information on species, gender and behavior.|
|Fixed arrays have been deployed from FLIP in three configurations:
1) vertical orientation allowing for omni-directional recordings of marine mammals;
2) horizontal orientation with the array suspended from a PVC frame 40 meters below the surface;
3) billboard configuration with the array connected to a PVC frame such that three hydrophones are suspended in the horizontal plane while two are positioned in the vertical plane.
On a typical FLIP deployment, all three array configurations are fixed in position to allow for long-term continuous acoustic monitoring of a study site.
Billboard array configuration (left)
|Credit: Elizabeth Henderson and Greg Campbell|