Metrics for characterizing the sources of ocean anthropogenic noise.

Abstract

Decibels are the standard shorthand for describing acoustic intensity and sound pressure level, but may lead to misunderstanding when applied as bioacoustic metrics. Acoustic power and source transmission energy are alternate metrics with intuitive appeal. Acoustic power, calculated from the acoustic intensity multiplied by the emitted solid angle, yields units of watts. Likewise, the energy per source transmission, given by multiplying acoustic power by the duration of the transmission, yields units of joules. For continuous (or quasicontinuous) signals, the standard procedure is to measure the root‐mean‐square (rms) of the signal. However, this presents problems for short duration signals where the duration of the signal being measured is an important parameter. In these cases it may be more appropriate to measure the peak‐to‐peak signal, rather than rms. Bandwidth is another important component of how the signal is described, typically in a narrow‐band for ambient noise and broad‐band for discrete sources. The characteristics of ocean anthropogenic noise sources in terms of these metrics will be discussed.