Study site: The northwestern inland waters surrounding the San Juan Islands and north to Johnstone Strait comprise a unique saltwater estuary marine environment formed by the outflow of Canada's Fraser River. Three pods of resident orcas frequent the OVAL site on San Juan Island during the spring and summer. The whales often vocalize in this area, presumably while pursuing salmon and socializing.

 

Hydrophone Array: 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.

 

Hydrophone Locations: This map shows hydrophone locations determined by sending frequency encoded pings to the array from an underwater speaker deployed at a variety of depths below a small boat whose location was determined via GPS. These pings were sent from the control computer via radio to the underwater speaker so that the precise travel time between the speaker location and each hydrophone could be determined. The speed of sound in water was measured at the same time and the hydrophone locations were calculated with an estimated location error of +/-2m. Determining accurate hydrophone locations has been the most difficult part of this project.

The underwater topography at OrcaSound gradually slopes to depth minimizing signal complexity due to multiple paths.

Take a look at the sound signals.