Fig. 3. Results from the transmission loss measurements and acoustic ranging calibration, using an omni-directional calibrated sound source emitting harbour porpoise clicks at a known range from 3 m depth. (A) Received level (dB re 1 µPa pp) as a function of measured range for the 4-hydrophone array. The line is a transmission loss model consisting of spherical spreading and absorption. (B) RMS error (see text) in acoustic localization as a function of the measured range for the 4-hydrophone array and the 3-hydrophone array. (C) The maximum variation in the transmission loss due to ranging variation as a function of measured range for the 4-hydrophone array and the 3-hydrophone array.