Lecture Halls - Room Acoustics and Sound Reinforcement

Kurt Eggenschwiler, Laboratory of Acoustics, Empa Materials Science and Technology, CH-8600 Duebendorf, Switzerland

Forum Acusticum 2005, Budapest


In this paper our experience with room acoustics, sound reinforcement and audio frequency induction loop for hearing impaired in lecture-halls is reported. The optimal reverberation time and the supporting geometrical conditions for classrooms are well known since a long time. Recent research confirms basically these findings, but it gives new requirements for shorter reverberation times. However, many of the existing lecture halls do not fulfill these conditions. In addition, many of the installed reinforcements systems have multiple lacks. Poor performance can be prevented by serious planning using nowadays easily available tools like computer simulation software, by using well adapted loudspeakers and by minimizing electronic processing. In Switzerland the state of the art in planning reinforcement systems is summarized in a publication for architects and owners. In this publication requirements are given for successful planning and construction of such systems. Measurements of reverberation time and speech intelligibility index STI in several lecture halls showed good results, when these requirements are fulfilled. Special attention has to be given to the legitimate request of hearing impaired people. But the installation of audio frequency induction loop systems in lecture-halls is a difficult task. Most lecture-halls are built side by side or one above the other. It has to be avoided that the induction loops disturb each other. A big effort has to be done to convince owner and architects of the importance of a good intelligibility in lecture halls for normal hearing and hearing impaired humans.I

Kurt Eggenschwiler
EMPA Abteilung Akustik
Überlandstrasse 129
CH-8600 Dübendorf
Tel. +41 44 823 41 77
Fax. +41 44 823 47 93
E-Mail: kurt.eggenschwiler@empa.ch