The standard defines several single-number quantities to evaluate acoustic performance: Spatial Decay Rate of Speech ( D2,Scap D sub 2 comma cap S end-sub
): The reduction in sound pressure level (dB) when the distance from a speaker is doubled. Speech Level at 4 Meters ( DIN EN ISO 3382 3 E 2021 02 pdf
): The average steady-state noise from HVAC or masking systems. Measurement Requirements INTERNATIONAL STANDARD ISO 3382-3 DIN EN ISO 3382 3 E 2021 02 pdf