Many studies of ambient ocean noise have focused on anthropogenic, biological, and weather- related sources, but collisions of sediment grains can also generate a significant amount of background noise.
In an observational study linking noise and sediment processes, Bassett et al. measured sediment-generated noise in Admiralty Inlet, Puget Sound, Washington, a site where peak tidal currents exceed 3 meters per second (6.7 miles per hour).
They find that sediment-generated noise is the dominant noise source with frequency between 1 kilohertz and 30 kilohertz during periods of strong currents. Peak sediment-generated noise levels from 4 to 20 kilohertz were associated with mobile gravel and pebbles.
In fact, the researchers find that during periods of strong currents, sediment-generated noise actually exceeded the noise from local ship traffic, and that intermittent events can increase noise levels by more than 10 decibels over periods of seconds.
Source: Journal of Geophysical Research-Oceans, doi:10.1002/jgrc.20169, 2013doi:10.1002/jgrc.20169