There are three fundamental conditions that must be satisfied when specifying acoustical treatment for a meeting room:
1. Ambient Noise
Ambient noise for a class/meeting room should not exceed NC=35dB. In most rooms of this type this is a function of the HVAC system, but may also require isolation from adjoining spaces including the AV equipment closet.
2. Sound Intelligibility
While most meeting rooms cannot have a true reverberant field, intelligibility quickly suffers if the decay rate of sounds within the room exceeds .5 to .75 seconds. Normal carpet treatment and acoustical ceilings are usually successful at controlling high frequencies, but low and mid frequencies will mask frequencies critical for speech intelligibility if not treated.
3. Local Acoustics
Local acoustics in this context refer to ceiling surfaces directly above non-reinforced conversations (as in a round table discussion). It is desirable to get some passive reinforcement from the room when people are communicating face to face at the same time that it is undesirable for sound to travel long distances across a room where it will interfere with other conversations.