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Abstract
Au WW, Green
M. "Acoustic interaction of humpback whales and
whale-watching boats," Marine
Environment Research,
2000, 49:5 (June), 469-81
The underwater
acoustic noise of five representative
whale-watching boats used in the waters of west Maui was measured in
order to study the effects of boat noise on humpback whales. The first
set of measurements were performed on 9 and 10 March, close to the peak
of the whale season. The ambient noise was relatively high with the
major contribution from many chorusing humpback whales. Measurements of
boat sounds were contaminated by this high ambient background noise. A
second set of measurements was performed on 28 and 29 April, towards
the end of the humpback whale season. In both sets of measurements, two
of the boats were inflatables with outboard engines, two were larger
coastal boats with twin inboard diesel engines and the fifth was a
small water plane area twin hull (SWATH) ship with inter-island cruise
capabilities. The inflatable boats with outboard engines produced very
complex sounds with many bands of tonal-like components. The boats with
inboard engines produced less intense sounds with fewer tonal bands.
One-third octave band measurements of ambient noise measured on 9 March
indicated a maximum sound pressure level of about 123 dB re 1 microPa
at 315 Hz. The maximum sound pressure level of 127 dB at 315 Hz was
measured for the SWATH ship. One of the boats with outboard engines
produced sounds between 2 and 4 kHz that were about 8-10 dB greater
than the level of background humpback whale sounds at the peak of the
whale season. We concluded that it is unlikely that the levels of
sounds produced by the boats in our study would have any grave effects
on the auditory system of humpback whales.
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