Abstract:
A model is developed for the prediction of the seismo-acoustic noise spectrum
in the microseism peak region (0.1 to 0.7 Hz). The model uses a theory developed
by Cato [J. Acoust. Soc. Am., 89 , 1096-1112 (1991)] for an infinite depth
ocean in which the surface orbital motion caused by gravity waves may produce
acoustic waves at twice the gravity wave frequency. Using directional wave spectra
as inputs, acoustic source levels are computed and incorporated into a more
realistic environment consisting of a horizontally stratified ocean with an elastic
bottom. Noise predictions are made using directional wave spectra obtained from
the SWADE surface buoys moored off the coast of Virginia and the SAFARI sound
propagation code, with a bottom model derived using wave speeds measured in
the EDGE deep seismic reflection survey. The predictions are analyzed for noise
level variations with frequency, wave height, wind direction, and receiver depth.
These predictions are compared to noise measurements made in ECONOMEX using
near-bottom receivers located close to the surface buoys. Good agreement is
found between the predictions and observations under a variety of environmental
conditions.
