This part of IEC 60534-8 defines equipment, methods, and procedures for obtaining laboratory measurements of sound pressure levels radiated by control valves and/or associated piping configurations, including fixed restrictions, through which compressible fluids are passing. Control valves discharging to atmosphere are excluded from this standard. Method A is a uniform method of measuring the radiated noise from the valve and associated test piping and allows a comparison of various measuring results which is beneficial for both user and manufacturer. The noise criteria are expressed by determining the sound pressure level of the valve under consideration. Method B is a procedure for measuring the sound pressure levels within pipe systems upstream and downstream of the valve under fixed operating conditions. Since inaccuracies due to the pipe transmission are eliminated, this method is preferred for evaluation of the acoustical characteristic of valves. The noise characteristics to be determined are useful for the following reasons: a) to compare the performance of different valves; b) to plan measures for noise abatement; c) to determine acoustical characteristics of valves and valve assemblies; d) to enable proper sizing of sound absorbers; e) to determine possible adverse effects on ultra-sonic flow meter measurements.