This part of IEC 62127 specifies methods of use of calibrated hydrophones for the measurement in liquids of acoustic fields generated by ultrasonic medical equipment operating in the frequency range up to 40 MHz. The objectives of this standard are: - to define a group of acoustic parameters that can be measured on a physically sound basis; - to define a second group of parameters that can be derived under certain assumptions from these measurements, and called derived intensity parameters; - to define a measurement procedure that may be used for the determination of acoustic pressure parameters; - to define the conditions under which the measurements of acoustic parameters can be made in the frequency range up to 40 MHz using calibrated hydrophones; - to define procedures for correcting, for limitations caused by the use of hydrophones with finite bandwidth and finite active element size. 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.