Directional acoustic
sensing using theNoiseSpotter®
Kaus Raghukumar
Frank SpadaGrace Chang

September 29, 2023

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Motivation•

Instrumentation that will facilitate acoustic
data collection as a means to reduce risk andstreamline environmental permitting•

Expected source intensity levels 106-109 dB
re 1 µPa in 125-250 Hz range, 25 m fromsource (Tougaard et al. 2015)•Source localization can help isolate device
noise from other sounds•

Real-time characterization can help with
mitigation efforts.

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Sources of sound in the oceanNoiseSpotter® Sensitivity

Adapted from www.dosits.org
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Methods• NoiseSpotter® passive
acoustic monitoring
system offshore of theCalWave xWave™ WEC• Each sensor measuresacoustic pressure and3D particle motion, 50
Hz-3 kHz• Water depth 18-25 m• Sensor spacing:• Vertical: 35 cm, 50cm, 70 cm above
sea bed.
• Horizontal: 1 m
separation• Sensors enclosed in flow
noise-removal shields
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4

November 2021 deployment
DateObjective

November 13 Mobilization
November 14 NoiseSpotter® asdrifting system, alongwith DAISY
November
15-16

Real-time
NoiseSpotter®

November
17-18

Non-real time
NoiseSpotter®, 100 m
and 200 m from WEC
along four cardinal
directions

November
19-22

Multi-day non-real time
NoiseSpotter®

November 22 Demobilization
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5

WEC versus boat sounds
WEC

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Boat

6

CalWave deployment: azimuthal
anisotropy
WEC

Boat

Z-velocity

Not for Third-Party DistributionCalWave WEC sounds
WEC

Boat

Z-velocity

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Helicopter sounds
WEC

Boat

Z-velocity

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Boat
WEC

Boat

Z-velocity

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Gray whale?
WEC

BoatSource
WEC
Z-velocity
Boat

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LE,60 s(dB re 1 µPa2 s)
139 dB re 1 µPA
147

Helicopter

140

GrayWhale

138 dBHumpback Whale

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Directional Processing

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13

Ongoing NOAA OER projectNot for Third-Party Distribution

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Conclusions❯ WEC sounds at considerably lower
levels than ambient sounds suchas boats❯ Directional processing helps
isolate WEC sounds frombackground❯ Some directional anisotropy, likely
due to bathymetric variability
around WEC

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Acknowledgements❯ Garrett Staines, Joe Haxel (PNNL)❯ Brian Polagye (UW)
❯ Aaron Thode (SIO)❯ Sarah Henkel, Taylor Chapple,
Scott Heppell (OSU)

This report was prepared as an account of work sponsored by an agency of the UnitedStates Government. Neither the United States Government nor any agency thereof, nor
any of their employees, makes any warranty, express or implied, or assumes any legal
liability or responsibility for the accuracy, completeness, or usefulness of any information,apparatus, product, or process disclosed, or represents that its use would not infringe
privately owned rights. Reference herein to any specific commercial product, process, orservice by trade name, trademark, manufacturer, or otherwise does not necessarily
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thereof.

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