Comparison of the Underwater Ambient Noise Measured in Three Large Exhibits at the Monterey Bay Aquarium and in the Inner Monterey Bay
NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF PHYSICS
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Ambient underwater acoustic-noise recordings were made in three large exhibits at the Monterey Bay Aquarium and the inner Monterey Bay, with the results reported here. Observed broadband 0-6.4 kHz acoustic noise levels ranged from 112-125 dB re 1 microPa for the aquarium exhibits under normal operating conditions. Broadband acoustic noise levels of 113 dB and 116 dB re 1 microPa were observed for the nearshore and offshore bay locations, respectively. A comparison of the noise spectrum in the aquariums largest exhibit to that of the environment which it attempts to simulate, the offshore bay, revealed a higher noise level of approximately 15-25 dB in the exhibit for frequencies between 20 Hz and 6.4 kHz. A similar comparison of the noise spectra of the two smaller exhibits and the nearshore bay location revealed a difference of approximately 5-10 dB across the entire frequency range of 0-6.4 kHz. Aquarium measurements with various mechanical equipment motors, fans, pumps, sprinklers, wave machine turned on and off highlighted some of the prominent ambient noise contributors. It was concluded that the pump machinery is the greatest contributor to ambient noise, with the strength directly related to the exhibits proximity to the machinery room.