Too much reverberation has a negative impact on the intelligibility of speech. This can, for example, make it hard to hear what a class teacher is saying.
Reverberation is also particularly noticeable in a place of worship where the sound may be heard for several seconds while it fades away. The main reason religious leaders pronounce their words clearly and talk slowly, leaving small gaps between sentences, is to overcome this reverberation and make their speech clear (such a manner of speaking also has a beneficial side-effect of sounding reverent).
Conference rooms are an especially challenging acoustic environment. Collaborative white boards, stylish glass walls and the obligatory large table are all highly-reflective surfaces for sound. This tends to increase the reverberation time of the room which impacts speech intelligibility.
Typically, reverberation times can be reduced by damping using absorbing materials such as thick carpets, curtains, upholstered furniture or dedicated sound-absorbing panels. Furthermore, the presence of people in a room reduces the reverberation, and therefore produces a lower reverberation time value compared to the unoccupied room.
On the other hand, too little reverberation will reduce the rich, warm acoustic sound from an orchestra in a concert hall.