This International Standard establishes: - The general concept of the limits of applicability of acoustic measurements in water resulting from finite-amplitude acoustic effects. - A method to ensure that measurements are made under quasi-linear conditions in order to minimise 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 gain up to 12; - at all depths for which the maximum acoustic pressure in the plane perpendicular to the acoustic axis lies on the axis; - to both circular and rectangular source geometries; - to both continuous-wave and pulsed fields. - The definition of an acoustic quantity appropriate for establishing quasi-linear conditions. - A threshold value for the acoustic quantity as an upper limit for quasi-linear conditions. - A method for the estimation of attenuated acoustic quantities under conditions of nonlinear propagation in water.