IEC 60534-8-4:2015 establishes a method to predict the noise generated in a control valve by liquid flow and the resulting noise level measured downstream of the valve and outside of the pipe. The noise may be generated both by normal turbulence and by liquid cavitation in the valve. Parts of the method are based on fundamental principles of acoustics, fluid mechanics, and mechanics. The method is validated by test data. This third edition cancels and replaces the second edition published 2005. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) Hydrodynamic noise is predicted as a function of frequency and b) Elimination of the acoustic power ratio.