Realization and Dissemination of Unit Watt in Airborne Sound: Measurement Methodology, Sound Emission Regulations and Implications

The study focusses on two major aspects: measurement methodology and uncertainty in the realization and dissemination of unit watt in airborne sound and consideration in legal sound regulations for various noise sources. Although sound power level is the fundamental unit invariant of distance from the source, yet there is no direct method for its measurement. An National Metrology Institute (NMI) perspective for the realization, dissemination and application of acoustical quantities: sound pressure and sound power level for strengthening the measurement traceability chain in India and formulation of legal noise limits and regulations of various noise sources is described. The low frequency limitations may yield different results using different methods, which thus necessitates the use of a harmonized approach in realizing the sound power parameter for improving the traceability for the unit watt in airborne sound. The use of sound power level and sound pressure level for noise labeling of appliances and other noise sources in India is recommended.