Val Veirs Colorado College Colorado Springs, CO Source Levels of Orca (Orcinus Orca) Social Vocalizations Measured with a Shore-Based Hydrophone Array S-19 Call dB re 1  1m

Array of hydrophones is permanently deployed on the west side of San Juan Island, Puget Sound. Orca Vocalization and Localization -- OVAL

Each spring for the past 5 years a group of undergraduate physics majors from Colorado College have worked at the site – deploying, repairing, operating …

OVAL Hydrophone Array Four ITC hydrophones with student-build preamps are deployed on fixed, weighted stands in depths from 12 to 45 meters. The seafloor descends at a nearly uniform 30 o to depths of 200 m at 400m from the shore. The frequency bandwidth of these detectors is 100Hz – 10kHz and signals are digitized at Hz.

Southern Resident Orcas The three pods of Southern Residents, ~85 animals, pass by the OVAL array many times over the four month summer season – May to September. Sometimes they vocalize and sometimes they are close to the hydrophone array.

Localization via Cross Power Spectra and Matched Field Processing Minimization of composite error between source location modeled differences and observed differences finds best estimate of source location. Downhill Simplex: Cross Power Spectra for 3 Pairs of Hydrophones

Calibration of Hydrophone Array Chirps are sent to the hydrophones from J-9 underwater projector from known depths and GPS locations.

Accuracy of Source Locations Mean Error (m)Standard Deviation (m) East-West difference North-South difference0.714 Vertical difference2.921 Range difference

Spreading Model Chirps sent from J-9 at source level of 140 dB re 1  1 m show average decrease in received level with distance is close to cylindrical spreading.

Source Level Calibration Histogram of calculated source level for 50 chirps from underwater projector operating at 140 dB re 1  1 m.

Summer 2004 Orca Passbys The OrcaSound hydrophone array ran continuously from May through September. The system triggered on orca social vocalizations on 24 separate passbys on 19 different days. A total of 1.84 Gb of acoustic data was automatically recorded during these passbys. All of these signals passed amplitude vs time profile constraints designed to accept transient signals that include orca vocalizations.

445 Orca Calls Near the Array Selection Criteria:Events Passing: The localization must be of adequate quality (Q > 6) and the distance from any hydrophone and the localized position must be less than 400m (this distance is ~ twice the array aperture). 602 The frequency structure of the call must be “orca- like”. There must be a relatively small number of prominent peaks in the power spectra that persist continuously for periods of time ~ a half a second or more during the call. 456 A trained observer checked to hear and see if the recording is an orca vocalization. 445

Source Level Distribution 445 orca vocalizations within 400 m of hydrophones

Source levels from Richardson, “Marine Mammals and Noise” and recent dolphin report (Janick 2000) and manatee report (Phillips 2004) Reported Source Levels of non- Echolocation Vocalizations of Odontocetes Regression line: acoustic pressure (Pa) at one meter from vocalizing animal = 20 mass (metric tons)

Peculiar Bifurcation and Quiet Nights

Background Noise and Average Source Levels

Acknowledgement and Thanks March 2000: Tami Beitzel, Jonah Huckabay, Rois Langner, Vik Sarkar, Davis Thomson March 2001: Kat Baker, Hannes Hubmayr, Bethany Marsh, Amos Ngola March 2002: Anderson English, Paul Guidice, Winn Jewett, Peter Richardson, Michael Silk, Hillary Swanson, Erika Danforth, Matt Ayres, Molly Yoder-Williams March 2003: Luke Galli, Brian Hurlbutt, Winn Jewett, Bill Morton, Sara Schuster, Zach Van Hilsen March 2004: Liz Martin, Craig Peterson, Luke Roberts, Nick Santorsola, Max Stevens, Yulan Qing Colorado College Students: The Colorado College Physics Department and Faculty Research Committee The Whale Museum of Friday Harbor and Dr. Rich Osborne Leslie Veirs and Scott Veirs