Noise exposure metrics for auditory and nonauditory damage in aquatic animals

Abstract

The total acoustic energy flux is often used to correlate impacts of different types of sounds having various durations on marine animals. To calculate this metric, one must know both the acoustic pressure and particle velocity. But, in practice, the acoustic pressure is measured usually at just one point and the particle velocity is unknown. The total energy flux is then estimated by assuming the stimulus is an ideal plane wave and calculating the sound exposure level. The inner ears of many aquatic animals, however, respond directly to acoustic particle motion. In addition, because aquatic animals are acoustically coupled to the surrounding water, acoustic particle motion is also critical in estimating sound exposures that may cause damage to tissues outside the auditory system. Thus in noise impact studies, both pressure and local particle velocity must be measured to accurately estimate the total acoustic energy dose received by an aquatic animal. Several case studies taken from the literature will be presented to demonstrate how to estimate acoustic particle velocity from pressure gradient measurements in common aquatic animal testing environments and calculate the total acoustic energy flux.