Halls-Room Acoustics and Sound Reinforcement

This paper describes our experience with lecture halls with regard to the room acoustics, sound reinforcement and audio frequency induction loops for persons with hearing impairment. The optimum reverberation time and geometrical conditions for classrooms are well known. Recent research basically confirms this knowledge but indicates the need for shorter reverberation times. However, many existing lecture halls do not fulfill these requirements. Furthermore, too many existing reinforcement systems are deficient in a number of aspects. In Switzerland the state of the art in the planning and construction of reinforcement systems is summarized in a publication for architects and proprietors. Measurements of the reverberation times and speech intelligibility index STI in several lecture halls showed good results when these requirements are fulfilled. The needs of persons with hearing impairment must be carefully taken into account.