Kurt
Eggenschwiler, Laboratory of
Acoustics, Empa
Materials Science
and Technology, CH-8600 Duebendorf, Switzerland
Forum Acusticum 2005, Budapest
Abstract:
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