This European Standard specifies information additional to EN ISO 10140-1 necessary to carry out efficiently and under standardized conditions the determination of the sound reduction index of drywall systems of plasterboard with steel studs according to EN ISO 10140-2 "Acoustics - Laboratory measurement of sound insulation of -building elements - Part 2: Measurement of airborne sound insulation". Observe that all demands in EN ISO 10140-2 should still be fulfilled. In order to decrease the uncertainty, it specifies: additional guidelines for testing drywall systems of plasterboard with steel studs; and; a method to validate laboratory by using two reference test partitions. The results obtained are used to convert frequency-dependent sound reduction index into single number ratings, according to EN ISO 717-1. These performances can be used to compare different products, or, and to express a requirement, or, and as input into estimation methods, such as EN 12354-1.