期刊
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
卷 130, 期 2, 页码 679-682出版社
ACOUSTICAL SOC AMER AMER INST PHYSICS
DOI: 10.1121/1.3605541
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资金
- Netherlands Ministry of Defense [WO geluidsduur zee-zoogdieren 235-08-6006-01]
- Royal Netherlands Navy
Helicopter long range active sonar (HELRAS), a dipping sonar system used by lowering transducer and receiver arrays into water from helicopters, produces signals within the functional hearing range of many marine animals, including the harbor porpoise. The distance at which the signals can be heard is unknown, and depends, among other factors, on the hearing sensitivity of the species to these particular signals. Therefore, the hearing thresholds of a harbor porpoise for HELRAS signals were quantilied by means of a psychophysical technique. Detection thresholds were obtained for five 1.25 s simulated HELRAS signals, varying in their harmonic content and amplitude envelopes. The 50% hearing thresholds for the different signals were similar: 76 dB re 1 mu Pa (broadband sound pressure level, averaged over the signal duration). The detection thresholds were similar to those found in the same porpoise for tonal signals in the 1-2 kHz range measured in a previous study. Harmonic distortion, which occurred in three of the five signals, had little influence on their audibility. The results of this study, combined with information on the source level of the signal, the propagation conditions and ambient noise levels, allow the calculation of accurate estimates of the distances at which porpoises can detect HELRAS signals. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3605541]
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