Estimating the risk of temporary acoustic threshold shift, caused by hydroacoustic devices, in whales in the Southern Ocean

Abstract

There is a potential threat to marine mammals from acoustic signals emitted by hydroacoustic devices. The impact on the hearing of marine mammals depends on the technical parameters of the instruments and on the exposure of the animal to noise pulses, as well as on the properties of the biological system, that is to say, on the anatomy and the audiogram of the animal. Here, the blue whale, the sperm whale and the beaked whale are taken as examples in an investigation of the potential exposure to noise pulses from the hydroacoustic instruments Hydrosweep and Parasound. Diving depths of the whales and relative speeds of the animals with respect to the survey vessels are taken into account, as well as the area impacted by the equipment, in estimating the level of sound needed to produce “temporary threshold shift” in an animal. The results suggest that auditory damage is only likely if animals pass the transducer at close range and that the impact on marine mammals can be mitigated by implementing prior detection and shut down procedures.