This International Standard 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 International Standard are - To define a group of acoustic parameters which can be measured on a physically sound basis. - To define a second group of parameters which can be derived under certain assumptions from these measurements, and called derived intensity parameters. - To define a measurement procedure which 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.