A comparative study of sound propagation over land and water

Abstract

General experience by this author and others has shown that community noise problems are generally worse when the sound propagates over water. In order to study the differences, simultaneous measurements were made at like distances ranging from 15 to 500 m over land and water. Concurrent measurements were made of temperature gradients over the land and water. Wind effects were negligible. The sound propagation experiment was conducted using a broad band source. When the data was analyzed, the over land propagation exhibited a decay rate, substantially greater than 6 dB/octave (as expected) but propagation over water showed a 5.5 dB/octave decay rate. This is less than would be expected from spherical divergence alone and suggests the presence of a surface wave propagating at some lower order inverse R power. A surface wave with this energy is not predicted by any existing theory. Temperature gradient effects are also present but minor compared to ground cover absorption over land and the surface wave phenomena over water.