A simple approach for marine mammal noise-induced threshold shift prediction from down-the-hole piling noise exposure

Abstract

In assessing auditory effects on marine mammals from noise exposure, a dual-criterion is currently used by regulators to estimate the noise-induced threshold shift (NITS). Such criterion classifies anthropogenic noise into two mutually exclusive categories: Impulsive and non-impulsive. However, in real world situations, marine mammals are often exposed to complex noise field that contains both impulsive and non-impulsive components, thus makes it difficult or even impossible to accurately assess their NITS from noise exposure. One example is down-the-hole (DTH) pile installation, which generates both impulsive noise from percussive drilling/striking and non-impulsive noise from debris removal simultaneously. In this study, a relatively simple approach is proposed that employs kurtosis values to quantify the impulsiveness of two DTH piling noises datasets for six different marine mammal functional hearing groups. A kurtosis adjustment approach that has been suggested for predict human hearing loss from noise exposure was then used to build correction factors for estimation of NITS of marine mammals exposed to DTH piling noises. Further research on marine mammal NITS from complex noise exposure is needed to validate and improve this model.