The concept of “universal design” means accessibility for all in public buildings, and this includes the acoustical conditions. The acoustical challenges are particularly pronounced in restaurants and similar dining facilities. Elderly people and people with impaired hearing, in particular, rank restaurants high on the list of public spaces with serious acoustical problems. The most important noise source in a crowded restaurant is speech from conversations among other guests. When many people are gathered, speech noise can reach very high sound pressure levels if the room does not have a sufficient amount of sound absorption.

The “acoustic capacity” can be used to specify the maximum number of people in a restaurant that allows a sufficient quality of verbal communication for people with normal hearing, and this can serve as a guide for existing restaurants. However, reverberation time may be more convenient for defining acoustical requirements in new spaces. A closer study of the conditions for verbal communication in a noisy environment has shown that the volume per person is a key parameter in relation to reverberation time and communication distance. Maximum reverberation times as a function of volume per person are suggested for the purpose of sound classification of restaurants.