Is there an echo?
The most important factor in all regulations is reverberation time, which is defined as the time it takes for the sound pressure level to drop 60 dB below its original level.
In most cases, a low reverberation time improves the acoustical comfort. In some situations, however, such as concerts or conference halls, a higher reverberation time can improve listening comfort.
Reverberation time depends on the size and shape of the space along with the amount, quality and positioning of absorbing surfaces within the space. The more sound absorption in the room, the lower the reverberation time.