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The
Orca Vocalization and Localization (OVAL) Project uses an array of hydrophones
in the Haro Strait of Puget Sound to determine the location of vocalizating
orca whales
The OVAL Project is a joint research effort linking the Colorado College Physics Department with the Whale Museum of Friday Harbor, WA.. Our joint project is called SeaSound.
The director of the OVAL Project is Val Veirs, Professor of Physics at Colorado College
Vocalizations of orca whales may be divided into clicks and calls. Clicks
are short, broadband sounds used by orcas for echo-location. Calls have a
duration of a second or so and are presumably used for communication with
other orcas. A "Sonogram" or "Spectrogram" such as you
see here is a convient way to examine clicks and calls. This a graph of frequency
on the vertical axis and time on the horizontal axis. In this image, frequency
runs from 0 to 10 kHz and the time axis displays three or four seconds of
data. You see first a sequence of four clicks and then the harmonic structure
of an orca call.
Listen to this sequence of clicks and calls
At 3 pm on Wednesday, October 22, 2003 unusual orca vocalizations were recorded. (Click here to listen.) I observed an orca very close to one of OrcaSound's array of hydrophones. This orca's vocalizations have most of their power at about 8 kHz which is much higher than Southern Resident discrete calls. Simultaneously, a comercial fisher was finishing pulling in his purse seine. The orca (or possibly 2) milled around near a reef and when the fisher steamed off to the south, I observed an orca porpoising parallel to the boat, coming up for a breath and a splash every 10 sec or so.
Southern Resident Call Vocabulary: The three pods (J, K and L) that live in the southern portion of the Salish Sea between Vancouver and Seattle use a variety of calls that have been classified by John Ford (Vancouver Aquarium) with contributions by Rich Osborne (Whale Museum).
Ships and Boats make lots of noise in the waters the Southern Resident orcas frequent. Click here to listen and look at a variety of sources of underwater noise.
Here are some additional orca vocalizations. These are mp3 encoded.
Some Basic Sound Concepts: Click here for an
introduction to the terminology and concepts of marine acoustics.
The OVAL array of hydrophones is in the Haro Strait on the west side of San Juan Island. The array is comprised of eight ITC 4066 omnidirectional hydrophones. Signals from the hydrophones are amplified and filtered and brought to a Pentium III computer for data analysis.
The location of an underwater source is determined by determining the arrival time difference for a call or a click at each of the hydrophones in the array. From these time differences the location of the source can be found if the location of each of the hydrophones is well known.
From this page you can access the real-time data that is available at the
OVAL location on San Juan Island, WA.
Click HERE for realtime underwater noise levels
Click on the image below for weather data:
The population of orcas that frequent the OVAL site each summer is in critical
condition. This population was severly impacted thirty years ago when many orcas
were taken from this population for marine parks, especially SeaWorld. The population
appeared to be recovering from this assault until about five years ago. Since
then the population has dropped each year with the total dropping from a high
of 99 in 1995 to its current number of 78. (Population data is from the Center
for Whale Research) There are three
feasible components to the current drop in orcas. The problem may be some
combination of food, pollution, and pressure from whale watchers.
For
the last three years, Colorado College physics major students have worked
in the field installing and calibrating the OVAL array of hydrophones.
March 2002 Photos and Student Pages
The first results from OVAL were presented at the Biology of Marine Mammals biennial conference in Vancouver, Canada Nov. 28 - Dec. 3, 2001.
Spatial Relationships of Resident Killer Whale Vocalizations
Block 7 - 2003 PC462: Field Research in Physics: Boat Noise in Haro Strait"
May - 2003 Orca Source Levels"
May - 2003 Navy Source Levels"
On
the Shoulders of Giants
We have compiled an extensive bibleography of articles related to the OVAL
project. BIBLIOGRAPHY