This International Standard establishes:• The general concept of the limits of applicability of acoustic measurements in waterresulting from finite-amplitude acoustic effects.• A method to ensure that measurements are made under quasi-linear conditions in order tominimise finite-amplitude effects, which may be applied under the following conditions:- to acoustic fields in the frequency range 0.5 MHz to 15 MHz;- to acoustic fields generated by plane sources and focussing sources of amplitude gainup to 12;- at all depths for which the maximum acoustic pressure in the plane perpendicular tothe acoustic axis lies on the axis;- to both circular and rectangular s