Abstract In the first part of this paper, after underlining the diversity of large halls, both for social and cultural purposes, such halls are divided acoustically into four groups: Very noisy halls due to the high density of occupancy. Such halls are considered in terms of conversation without effort and include theatre foyers, lobbies, etc. Less noisy halls and ultimately more intimate rooms where announcements by public address systems are to be heard distinctly. This also applies to reception and waiting rooms. Halls where music is to be listened to and conversation is to be carried on without too much mutual interference as is also the case in restaurants, bars, etc. Very quiet halls intended to favour concentration of thought or artistic receptiveness (reading rooms, art galleries). The variety and intricacy of problems involved in the acoustic study of a particular hall and the impossibility of basing it on the usual methods of analysis are then examined. The main difficulty does not lie in the acoustic study itself but in persuading the architect to become conscious of its advantages. As long as acousticians are alone in emphasising the importance of acoustic studies at the design stage the chances of progress remain rare. An effort must be made to convince architects that acoustic processing, far from limiting the possibilities of creative expression, succeeds on the contrary in enhancing the architectural achievements. The use of well conceived lighting may also result in an important contribution in this respect. In order to illustrate the variety of aesthetic possibilities offered by acoustic processing, the hall in an office building has been taken as an example.