2012 COURSE DATES: AUGUST 4 – 17, 2012 - Sirenian International

636 MARINE MAMMAL SCIENCE, VOL. 23, NO. 3, 2007
A
Weighted Spectrum (dB)
B
Weighted Spectrum (dB)
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Weighted Spectrum for Vessel Approaches 15 s Before Peak
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Frequency (kHz)
Idle
Plane
PWC
Noise
Hearing Sensitivity
Weighted Spectrum for Vessel Approaches at Closet Point of Approach
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Idle
Plane
PWC
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Noise
Hearing Sensitivity
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Frequency (kHz)
Figure 3. Spectra of vessel approaches weighted by the manatee hearing thresholds and
smoothed in frequency plotted with ambient noise levels: (a) comparison of 2-s clips measured
15 s before the closest point of approach; (b) comparison of 2-s clips taken at the closest point of
approach. For illustration purposes the manatee hearing sensitivity values for the frequencies
measured in this paper are shown by the dashed-dotted line (data taken from Gerstein et al.
1999).
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Hearing Sensitivity (dB re 1 µPa)
Hearing Sensitivity (dB re 1 µPa)