Divergence of Boat Noise Above Water Level in a Downwind direction

Sound attenuation was investigated in the case of boat noise propagated above water level in a downwind direction. It was hypothesised that when measured downwind, the curving propagation path and the flat water level will result in a cylindrical divergence of sound energy, instead of a spherical divergence of the point sound source. Attenuation of the harmonic peaks associated with boat noise was determined as a function of distance. The results indicate that the sound waves show no spherical divergence from a point sound source when the sound is propagated in a downwind direction above the water level, instead the divergence appears to approximate cylindrical divergence.