[MARMAM] New Publication: Sonar inter-ping noise field during cetacean behavioral response studies in southern California

Shane Guan - NOAA Federal shane.guan at noaa.gov
Fri Apr 21 11:53:15 PDT 2017

Dear Colleagues,

We are pleased to announce our recent paper on sonar inter-ping noise field
during cetacean behavioral response study in southern California:

Shane Guan, Brandon L. Southall, Joseph F. Vignola, John A. Judge, D. Turo
*Sonar inter-ping noise field characterization during cetacean behavioral
response studies off Southern California*. *Acoustical Physics*. 63(2),
204-205. doi: 10.1134/S106377101702004X

The potential negative effects of sound, particularly active sonar, on
marine mammals has received considerable attention in the past decade.
Numerous behavioral response studies are ongoing around the world to
examine such direct exposures. However, detailed aspects of the acoustic
field (beyond simply exposure level) in the vicinity of sonar operations
both during real operations and experimental exposures have not been
regularly measured. For instance, while exposures are typically repeated
and intermittent, there is likely a gradual decay of the intense sonar ping
due to reverberation that has not been well described. However, it is
expected that the sound field between successive sonar pings would exceed
natural ambient noise within the sonar frequency band if there were no
sonar activity. Such elevated sound field between the pings may provide
cues to nearby marine mammals on source distances, thus influencing
potential behavioral response. Therefore, a good understanding of the noise
field in these contexts is important to address marine mammal behavioral
response to MFAS exposure. Here we investigate characteristics of the sound
field during a behavioral response study off California using drifting
acoustic recording buoys. Acoustic data were collected before, during, and
after playbacks of simulated mid-frequency active sonar (MFAS). An
incremental computational method was developed to quantify the inter-ping
sound field during MFAS transmissions. Additionally, comparisons were made
between inter-ping sound field and natural background in three distinctive
frequency bands: low-frequency (<3 kHz), MFA-frequency (3–4.5 kHz), and
high-frequency (>4.5 kHz) bands. Results indicate significantly elevated
sound pressure levels (SPLs) in the inter-ping interval of the
MFA-frequency band compared to natural background levels before and after
playbacks. No difference was observed between inter-ping SPLs and natural
background levels in the low- and high-frequency bands. In addition, the
duration of elevated inter-ping sound field depends on the MFAS source
distance. At a distance of 900–1300 m from the source, inter-ping sound
field at the exposure frequency is observed to remain 5 dB above natural
background levels for approximately 15s, or 65%, of the entire inter-ping
interval. However, at a distance of 2000 m, the 5 dB elevation of the
inter-ping SPLs lasted for just 7s, or 30% of the inter-ping interval. The
prolonged elevation of sound field beyond the brief sonar ping at such
large distances is most likely due to volume reverberation of the marine
environment, although multipath propagation may also contribute to this.

​The ​paper is available at:
https://link.springer.com/article/10.1134/S106377101702004X, or by emailing
me at shane.guan at noaa.gov.

Best regards,
Shane Guan

Shane Guan, Ph.D.

National Marine Fisheries Service
Office of Protected Resources
1315 East-West Highway, Suite 13826
Silver Spring, MD 20910

Tel: 301-427-8401
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