In the future, Onda Corporation is going to use the units Volts/MPascal since these are the most appropriate for the types of hydrophones we sell. However, the legacy units which we have inherited are the crazy dB with respect to 1 Volt per micro Pascal, which carry over from early work done with microphones in air. These units are about 240 dB from where we want to be typically. The following figure shows how a conversion is accomplished, including how one accounts for the impedance of the media when calculating the conversion from volts squared to intensity. Note that we assume the media is water, as other fluids could cause damage and void your warranty.
