Figure 3

Power spectral densities (PSD) of (a) sound pressure in decibels relative to 1 micropascal per second squared per hertz (above 100 Hz due to the capability of the recorder used) and (b) monoaxial particle acceleration in decibels relative to 1 (nanometre per second squared) squared per hertz of original recordings of boats and boat playbacks at experimental site along with ambient noise and ambient noise playbacks.