Responses of reference hydrophones under real ocean conditions

The project is collaboration between interested parties to determine the variation in the response of hydrophones when used under real ocean conditions, in particular how the responses vary with water temperature and depth of immersion. The effect of temperature and depth on transducer response was identified as a significant potential source of error in underwater acoustic calibrations during the recent Euromet comparison (Euromet ACOUS 480), in particular when measurement made in laboratory tanks are extrapolated to predict the response expected in the marine environment. The project may involve:

- Collating existing data on the variation of response of hydrophones with temperature and depth;

- Identifying methods which may be used to measure the variation in response (for example the Acoustic Pressure Vessel at NPL in the UK);

- Undertaking limited work to measure the variation in response of selected devices and comparing with existing data;

- Estimating the calibration corrections that may be required to account for the environmental conditions under which a hydrophone is used.