Christopher Jones         Senior Engineer         Ocean Acoustics Dept.         Applied Physics Laboratory         University of Washington      Michael Wolfson         Mathematician IV         Ocean Acoustics Dept.         Applied Physics Laboratory         University of Washington      Jeff Nystuen         Principal Oceanographer         Air-Sea Interactions & Remote Sensing Dept.         Applied Physics Laboratory         University of Washington      NOAA	Field measurements and acoustic propagation modeling are combined to analyze the acoustic environment in Haro Strait of Puget Sound, home to pods of southern resident killer whales. Haro Strait is a highly variable acoustic environment with active commercial shipping, whale watching, and Naval activity. Southern resident killer whales are of unique public concern in this area because of increasing anthropogenic noise levels that may interfere with the animals' foraging strategies and behavior. Perspective view of Haro Strait bathymetry; scale in meters. Of principle concern in this research are background sound levels created by commerical shipping traffic or other persistent sound sources that propagate from the main shipping channel. Acoustic modeling is used to complement field measurements, as the shallow water environment of Haro Strait is far too complex, and the geo-acoustic parameters of the area are not characterized well enough to rely on modeling alone. Spectrogram of PAL data for a single day. Color scale represents dB. The field data were collected by a Passive Aquatic Listener (PAL) that was moored just off the coast of San Juan Island near the main shipping channel of Haro Strait. PALs are autonomous acoustic recorders consisting of a broadband, low-noise hydrophone, a signal processing board, a low-power microprocessor and a battery pack. The hydrophone extends from one end. The PAL is not a continuous acoustic sampler. The basic data are a time series of spectral levels. The interval between samples is chosen depending on the intent of the deployment. Typically the interval is several minutes. Between data samples, the PAL processor enters a 'sleep' mode to conserve batteries. A Passive Aquatic Listener in a deployment cage The data collection intervals are not designed to capture short duration signals, but occasionally PALs do capture marine mammal vocalizations during the periods when they are 'awake' and sampling the acoustic environment. A collection of whale vocalizations are available from the Haro Strait PAL data. Listen >>