Acoustic radiation from a submerged pile during pile driving

Pile driving with an impact hammer is inherently a transient process and can produce very high sound levels. It is shown that the underwater noise during pile driving is due to a radial expansion of the pile that propagates along the pile after impact. This structural wave produces a wave front cone in the water, and a downward moving wave that continues into the sediment. An upward moving wave front is produced in the sediment after the first reflection of the structural wave, which is subsequently transmitted into the water. This process is repeated to produce an acoustic field that consists of wave fronts with alternating positive and negative angles. Good agreement in the estimate of the angles was obtained between a finite element wave propagation model and measurements taken during a full scale pile driving study.