Over recent years there has been growing concern about the potential detrimental effects of underwater man-made noise on marine wildlife. This report, produced by the Sea Watch Foundation, is concerned with the sounds emitted by airguns used in seismic survey operations to find oil and gas deposits below the seabed. Sound source levels of airguns are generally greatest at the lower frequencies (50-140Hz) although the report also describes work which found significant levels of energy at much higher frequencies (1-20kHz) closer to the source.