Noise spectral density of the fatiguing stimulus, recorded from the calibration position in the test pool. The center frequency of the octave band is and the octave-band level is approximately re: .
Baseline (pre-exposure), exposure, and recovery thresholds for a sea lion, a harbor seal, and an elephant seal exposed to octave-band noise centered at . The test frequency was . The values indicate statistical significance of comparisons between conditions. In all cases, exposure thresholds were significantly greater than baseline thresholds, and there was no difference between baseline and recovery thresholds. In all but one case, recovery thresholds were significantly lower than exposure thresholds. Points refer to mean thresholds obtained over multiple sessions; error bars denote standard deviations.
Mean threshold shifts for three exposure levels and three exposure durations. Threshold shifts were measured at 2500 or following exposure to octave-band noise centered at . Control sequences duplicated the exposure sequences, with the exception that no noise was presented. Brackets show differences between individual groups of data. ( ; ; ; all other comparisons are not significant.)
Threshold shifts at center frequency of noise band following 25 and of SL noise exposure. Points denote individual threshold shifts determined from test sequences. Open squares denote mean threshold shifts. ( ; significant.)
Threshold shifts at center frequency of noise band following of exposure at SL and of exposure at SL. Points denote individual threshold shifts determined from test sequences. Open squares denote mean threshold shifts. ( significant.)
Linear regression plots of TTS vs sound exposure level at center frequency of noise band for the three subjects. Line slopes, significance, and -squared values are provided in the legends. The horizontal lines are zero-shift lines provided for reference.
Nonlinear regression plots of TTS vs sound exposure level at center frequency of noise band and one-half octave higher for the three subjects. See the text for an equation and significance of the model parameters. Solid curves represent exponential increase of TTS with increasing SEL. The horizontal lines are zero-shift lines. Dotted straight lines project TTS onset to linear portion of curve at higher exposure levels.
Combined nonlinear regression plot of TTS vs normalized sound exposure level (referred to individual thresholds; includes half-octave data). See the text for details.
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