): The average steady-state noise from HVAC or masking systems. Measurement Requirements INTERNATIONAL STANDARD ISO 3382-3
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 DIN EN ISO 3382 3 E 2021 02 pdf
): The distance from a speaker where the Speech Transmission Index (STI) falls below 0.50, the point at which concentration starts to improve. Background Noise Level ( Lp,A,Bcap L sub p comma cap A comma cap B end-sub ): The average steady-state noise from HVAC or
): 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
Lp,A,S,4mcap L sub p comma cap A comma cap S comma 4 m end-sub