Orcasound lab: a soundscape analysis case study in killer whale habitat with implications for coastal ocean observatories

Orcasound app and Orcasound Lab

Our study site: centered in summertime critical habitat of SRKWs cabled, calibrated hydrophones <100 m from shore bottom-mounted at depth of ~10 m 1-2 km to busy shipping lanes in Haro Strait (ship sources) ~2 km to entrance to Roche & Snug Harbors (boat sources)

Acoustic data and methods

One year of underwater noise recordings (11/2016 - 11/2017)

ITC 6050C hydrophone Calibrated via Interoceans Calibration system Stored as 16 bit WAV files at 44200 Hz sampling rate Analyzed 1-sec RMS received levels (dB re 1 uPa) in 3 bands: Broadband (10-22050 Hz) Call-weighted (500 - 5000 Hz) Click-weighted (5000 - 22050 Hz) Automatic Information System (AIS) data Logged for all AIS vessels with range <10 km Converted to local UTM coordinates, then bearing & range

2017 vessel behavior and noise study

Collaboration with NEMES

Images taken on daytime duty cycle, starting in August, 2017.

NEMES camera methods:

Measure range, speed, & received levels of boats

• Locate boat in each frame with Theo (custom QT program)
• Compute time of closest point of approach (CPA)
• Compare with time of acoustic peak(s)

NEMES camera methods:

Video of 20 knot boat with computed range determining source level.

Broadband received level peaks

Ships and boats have similar maxima, but ships last longer

Peak validation example: 2 ships, boats, & SRKWs

Peak validation example: killer whale calls

Peak validation example: overlapping vessels

Broadband received level quantiles: seasonal and diurnal differences

Quantiles of the broadband noise over a one year period (2017) The y-axis is the percentage of the time that the dB level is less than the corresponding x-value. In the summer a day/night difference appears because of the summertime presence of lots of speedboats. Boats raise the median (50% quantile) dB levels 5 dB in the day compared to the night. This effect is more prominent below the median noise level as boat noise is itself most frequent at lower dB levels. In the winter there is little difference between day and night.

Broadband summer received level quantiles

How does the cumulative distribution change upon removal of local anthropogenic sources?

Legend: Received levels from all sources RL without ships RL without ships or boats Removing ships reduces the median by 2 dB and the 75% by 4 dB Now removing boats drops the median one more dB.

New noise metrics from local quantiles?

"Urban ambient" noise levels?

Background levels based from time series of receive level with local anthropogenic sources removed.

Proposal for new acoustic metrics

Urban ambient noise level: a baseline for "delta" noise metrics for SRKWs

Holt et al., 2017, Endangered Species Research

Questions?

Measurements of RL within the whale watching fleet

Griffin & Bain, 2006	Holt et al., 2009	Holt et al., 2017
Median 128 dB (0.1-100 kHz, 60s)	Mean 110 dB RMS (1-40 kHz, 0.25s)	Mean 108 dB RMS (1-40 kHz, 1s)

Proposal for new acoustic metrics (for orcas in an urban estuary? eleswhere?)

What baseline for computation of "delta" noise metrics?

Broadband summer received level quantiles

What if we achieved the Okeanos Pledge in the Salish Sea?
-3 dB every 10 years...

Legend: Received levels from all sources RL without ships RL without ships or boats Dotted line shows quantiles when detected ship receieved levels are reduced by 3 dB