Attempting to define sound exposure metrics for fish

One of the big issues in addressing the biological effects of sound on humans and animals is metrics. For fishes the issue is further complicated because their inner ear responds directly to acoustic particle motion and in some species, indirectly to pressure through multiple pathways. So, metrics based only on pressure can be misleading in developing sound exposure criteria. The decibel scale also confounds the problem because it is used to express not only levels of sound pressure, but also levels of sound power, intensity, and energy. Even for just sound pressure, decibels are used to express peak, peak-to-peak, and time-averaged values, which can hamper extrapolation of laboratory data to anthropogenic sources in the field. Add to that the changes in decibel reference values when going from air to water, more than 25 000 different fish species, and the fact that a significant amount of sound exposure research on fish has been done in small enclosures at low frequencies, and one quickly realizes the difficulties in developing meaningful relationships between sound exposure and observed effects. This presentation will focus on relevant sound exposure metrics, their practical definitions, and their application to quantifying the biological effects of sound on fish.