This International Standard is applicable to:- hydrophones employing piezoelectric sensor elements, designed to measure the pulsed and continuous-wave ultrasonic fields generated by ultrasonic equipment;- hydrophones used for measurements made in water;- hydrophones with or without an associated pre-amplifier;This International Standard specifies relevant hydrophone characteristics.Associated standards deal with hydrophone calibration (IEC 62127-2) and their use characterizing ultrasonic fields (IEC 62127-1), including comprehensive lists of references.