| Popis: |
The West Indian manatee has become endangered partly because of watercraft collisions in Florida’s coastal waterways. Several boater warning systems, based upon manatee vocalizations, have been proposed to reduce the number of collisions. One aspect of the feasibility of an acoustically based system will rely upon the distance in which a manatee vocalization can be detected. The magnitude of environmental noise and manatee vocalizations, as well as the acoustic spreading properties of the habitat will help to estimate the detection range of a manatee. This study surveyed several shallow‐water coastal areas in Florida (Crystal River, Cedar Key, and Indian River) which are likely to be inhabited by manatees. Using a chirp signal (1–10 kHz) broadcast by an underwater transducer, it was observed that the acoustic pressure data collected was best represented by the mixed and Lurton spreading models. The overall data obtained from passing a boat directly over the hydrophone was most closely represented by a spherical spreading model. However, for a boat that is approaching, a mixed spreading model is the most appropriate. The mean SPL for boat traffic was measured to be 140 dB and the background environment noise level ranged between 69 and 105 dB. |
