Masked hearing thresholds of a beluga whale (Delphinapterus leucas) in icebreaker noise

An experiment is presented that measured masked hearing thresholds of a bel uga whale at the Vancouver Aquarium. The masked signal was a typical beluga vocalization; the masking noise included two types of icebreaker noise and naturally occurring icecracking noise. Thresholds were measured behavioral ly in a go/no-go paradigm. Results were that bubbler system noise exhibited the strongest masking effect with a critical noise-to-signal ratio of 15.4 dB. Propeller cavitation noise completely masked the vocalization for nois e-to-signal ratios greater than 18.0 dB. Natural icecracking noise showed t he least interference with a threshold at 29.0 dB. A psychophysical analysi s indicated that the whale did not have a consistent decision bias. (C) 199 8 Elsevier Science Ltd. All rights reserved.