International Standardization in Underwater Sound Measurements

A round-robin program of hydrophone calibrations was organized by a committee of the International Electrotechnical Commission to determine the spread in values obtained by participating international agencies in calibrating the same group of hydrophones. The results were expected to permit specifying a practical figure for accuracy of measurement and to provide information that could be used to design an international standard hydrophone for underwater sound measurements. The calibration facilities and methods used by each of the nine participants are described, as well as the construction of the hydrophones. Ten graphs show the calibration results obtained by each nation. The conclusion is that calibrations agree more closely when the hydrophone has some amount of vertical directionality. The average deviation of all data is ±0.6 dB.