This part of IEC 62127 specifies: - absolute hydrophone calibration methods; - relative (comparative) hydrophone calibration methods. This standard is applicable to - hydrophones used for measurements made in water and in the ultrasonic frequency range up to 40 MHz; - hydrophones employing circular piezoelectric sensor elements, designed to measure the pulsed wave and continuous wave ultrasonic fields generated by ultrasonic equipment; - hydrophones with or without a hydrophone pre-amplifier. IEC 62127-1, IEC 62127-2 and IEC 62127-3 are being published simultaneously. Together these cancel and replace IEC 60866:1987, IEC 61101:1991, IEC 61102:1991, IEC 61220:1993 and IEC 62092:2001.