Abstract
One-hundredth-scale sea surfaces simulating seas up to B Beaufort 6 were generated with a wave maker. The average rms sound pressure transmitted through the surface to a farfield receiver in water was measured routinely, as were, on occasion, narrowband pressure level probability densities. The experiments covered a wide range of (full-scale) parameters: acoustic frequencies from 30 Hz to 1 kHz, receiver depression angles from 2° to 90°, and source heights from 50 to 1200 ft. The sound path was oriented parallel, antiparallel, and perpendicular to the sea direction. For surfaces with rms slopes of 4° or more, transmission gains, relative to smooth surface transmission, of up to 7 dB, were observed for shallow depression angles and all source heights, while relative transmission losses up to 5 dB occurred for moderate depression angles and sources up to 200 ft (full scale). The results can be explained by including a most-probable slope of 3° to 4° in the surface slope probability density.
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