Long time-base observations of surf noise

A year of surf noise observations in the very near shore region of La Jolla Shores beach are presented. Ambient sound levels and surface wave height were recorded for 9 min every hour from July 1997 through June 1998 at a monitoring station located 360 m seaward of the beach in 8-m deep water. Sound segments that were dominated by the noise from breaking surf formed the basis of a correlation analysis between surf noise level and wave height, wave period, wind speed, and mean water depth. The analysis shows that surf noise is primarily determined by wave height, and scales approximately with the wave height squared. The surface wave energy flux onto the beach also scales with wave height squared, leading to the conclusion that the conversion of the mechanical energy of the surface wave field into noise energy is approximately constant. In fact, the ratio of noise energy to surface wave energy flux varies by up to a factor of 3 over the range of energy fluxes considered (100-3000 W per m).