808.2 Reverberation Time
For each of the octave frequency bands with center frequencies of 500, 1000, and 2000 Hz, the reverberation time (T60) shall not exceed the times specified below:
Reverberation times shall apply to fully-furnished, unoccupied classrooms. Reverberation times shall be field verified via measurements over a minimum 20 dB decay in each octave frequency band in accordance with ASTM E2235 listed in Section 106.2.13.
The Noise Reduction Coefficient (NRC) ratings for floor, wall and ceiling surface finishes shall conform to the following equations:
For a classroom with a volume less than or equal to 10,000 cubic feet (285 m3):
For a classroom with a volume between 10,000 cubic feet (285 m3) and 20,000 cubic feet (565 m3):
NRCFloor = NRC rating of the floor finish material
SFloor = floor area in square feet
NRCCeiling = NRC rating of the ceiling finish material
SCeiling = ceiling area in square feet
NRCWall = NRC rating of the wall acoustical treatment
SWall = wall treatment area in square feet
Volume = room volume in cubic feet
Where a floor, ceiling or wall has multiple surface finishes, the NRC x S product for each surface finish shall be added to the left side of the equation.