Ocean Sounds

OLYMPUS DIGITAL CAMERAThe ocean continuously radiates infrasound. The ocean processes that produce microseisms on seismometers and hydrophones produce microbaroms in the atmosphere. Breaking ocean waves also produce sound that scales with the breaker height and type.

Surf Infrasound

Surf Infrasound from Moorea

In order to further our understanding of the relationship between breaking ocean waves and infrasound, we conducted an experiment on the island of Moorea in French Polynesia . The Temae reef on the northeast coast of Moorea provided a well constrained experimental environment where individual breaking waves could be identified and recorded. The steep bathymetry and proximity to land of the reef shelf permitted synchronous wave height, infrasonic, seismic, and visual recordings of individual waves breaking against the shallow reef ledge. We characterize a source mechanism for surf infrasound and demonstrate the capability to acoustically track alongshore traveling (peeling) plunging waves.

(surf moorea lp 4ps)

Surf infrasound sped up by a factor of 50

Microbarom Infrasound

Like their seismic equivalent, microseisms, microbaroms are believed to be generated by speaker-like vertical ocean displacement induced by nonlinear interactions between trains of waves traveling in nearly opposite directions with similar frequencies. While microseisms are generated by energy traveling vertically down through the water column, microbaroms are the part of the sound field that travels through the atmosphere near the horizontal. Microbaroms make up the bulk of the acoustic energy present in the 0.2-0.5 Hz frequency band, and thus act as a significant source of noise in the band used for nuclear treaty monitoring.

Hurricane and Typhoon Infrasound

Super Typhoon Bopha – December 2, 2012

Super Typhoon Haiyan – November 6, 2013