Speech intelligibility
The speech intelligibility in a room depends on the reverberation time and the background noise.
If a room has a long reverberation time, spoken words will not die out before the next words reach the listener. This results in poor speech intelligibility, and it will be difficult for the listener to understand what is said.
However, if the sound is absorbed, resulting in a short reverberation time, this provides a good acoustic environment and a high level of speech intelligibility.
But, there is not much point in having excellent acoustics if the background noise drowns out what is being said. This is where acoustic insulation is needed and that is an entirely different topic...
Previous: Sound absorption