A Vented Resonant-Pipe Projector

A moderate power, broadband projector is described that has potential applications in deep-towed seismic profiling and underwater acoustics research. It is a free-flooding, resonant-pipe device in which vent holes are introduced into the pipe walls to significantly increase the projector response between the first two resonances, which occur at 2300 and 4350 Hz. Selection of the hole size and position for the experimental unit was aided by finite-element analysis. The finite-element modelling of the projector is described and the theoretical and experimental results are compared. The projector has useful acoustic output over a two-octave band with electroacoustic efficiencies ranging between 20% and 72% over most of the band. The projector has no maximum depth limitation, but cavitation may limit its performance at shallow depths.