This work describes a semi-empirical method to predict A-weighted sound levels at a distance of one meter from the downstream pipe wall and one meter downstream of throttling valves when reducing pressure of flowing water. The method accounts for the sound produced by hydrodynamic sources associated with turbulence and/or cavitation within a valve. The method has uncertainties for pipe sizes exceeding 200 rum in diameter due to lack of available empirical data. The method has been validated using data from a variety of different valve sizes and valve types supplied by three different manufacturers. The accuracy of the method is primarily dependant on the exactness of the given "differential pressure ratio for incipient cavitation", and the "valve style coefficient", where the latter determines the hydraulic diameter of the submerged water jet exiting the valve's orifice. This method is intended to replace the existing IEC Standard 60534-8-4. (C) 2004 Institute of Noise Control Engineering.
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