Regulations designed to mitigate the effects of man-made sounds on marine mammal hearing specify maximum daily sound exposure levels. The limits are lower for impulsive than non-impulsive sounds. The regulations do not indicate how to quantify impulsiveness; instead sounds are grouped by properties at the source. To address this gap, three metrics of impulsiveness (kurtosis, crest factor, and the Harris impulse factor) were compared using values from random noise and real-world ocean sounds. Kurtosis is recommended for quantifying impulsiveness. Kurtosis greater than 40 indicates a sound is fully impulsive. Only sounds above the effective quiet threshold (EQT) are considered intense enough to accumulate over time and cause hearing injury. A functional definition for EQT is proposed: the auditory frequency-weighted sound pressure level (SPL) that could accumulate to cause temporary threshold shift from non-impulsive sound as described in Southall, Finneran, Reichmuth, Nachtigall, Ketten, Bowles, Ellison, Nowacek, and Tyack [(2019). Aquat. Mamm. 45, 125–232]. It is known that impulsive sounds change to non-impulsive as these sounds propagate. This paper shows that this is not relevant for assessing hearing injury because sounds retain impulsive character when SPLs are above EQT. Sounds from vessels are normally considered non-impulsive; however, 66% of vessels analyzed were impulsive when weighted for very-high frequency mammal hearing.
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April 2020
April 03 2020
Techniques for distinguishing between impulsive and non-impulsive sound in the context of regulating sound exposure for marine mammalsa)
Special Collection:
The Effects of Noise on Aquatic Life
S. Bruce Martin
;
S. Bruce Martin
a)
1
JASCO Applied Sciences Canada
, Suite 202, 32 Troop Avenue, Dartmouth, Nova Scotia, B3B 1Z1, Canada
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Klaus Lucke;
Klaus Lucke
2
JASCO Applied Sciences
, Australia, 1/14 Hook Street, Capalaba, Queensland 4157, Australia
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David R. Barclay
David R. Barclay
3
Department of Oceanography, Dalhousie University
, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
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a)
Also at: Department of Oceanography, Dalhousie University, 1355 Oxford Street, P.O. Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada. Electronic mail: bruce.martin@jasco.com, ORCID: 0000-0002-6681-9129.
a)
This paper is part of a special issue on The Effects of Noise on Aquatic Life.
J. Acoust. Soc. Am. 147, 2159–2176 (2020)
Article history
Received:
March 19 2019
Accepted:
March 11 2020
Citation
S. Bruce Martin, Klaus Lucke, David R. Barclay; Techniques for distinguishing between impulsive and non-impulsive sound in the context of regulating sound exposure for marine mammals. J. Acoust. Soc. Am. 1 April 2020; 147 (4): 2159–2176. https://doi.org/10.1121/10.0000971
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