RT60 is a single figure that may be OK to describe the required performance of an office or a worshop, but it is not sufficient to describe the acoustic performance of a specialised room. Such rooms include classrooms, multi purpose halls, auditoriums, music teaching rooms etc.

RT60 is calculated by averaging the reverberation time at 250, 500, 1000 and 2000Hz. For example, if the reverberations time were 0.9s at 250Hz, 0.7s at 500Hz, .06s at 1000Hz and 0.4s at 2000 Hz, the reverberation time would be

(0.9 + 0.7 + 0.6 + 0.4)/4 = 0.65s

In the graph above, an RT60 of 0.9 seconds could clearly be anywhere from very good to disastrous…..