This Technical Specification 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 focusing 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.