172 Chapter 7
to an adequately chosen geometry and size of the
surfaces involved in this reverberation-time generating
mechanism, it is possible to reduce the reverberation
time in the low frequency range in a desirable fashion,
while the sound impression is not deprived of its stimu-
lating sound energy by sound absorption measures. In
the concert hall of the Gewandhaus in Leipzig,^33 the
room has its widest extension in the rear audience area,
so that here, as a result of simulation measurements in a
physical model (see Section 7-3), the height of the
ceiling was chosen to have its maximum, Fig. 7-29A
and B. In contrast to that, the maximum room width of
the concert hall of the Philharmonie Berlin, Fig. 7-29C
and D is in the region of the platform. To realize an
optimum reverberation time, the maximum room height
has to be above the platform.
This also explains why it was necessary to arrange
room-height reducing panels in this concert hall. With
music, the ceiling above the performance zone must
neither fall below nor exceed a certain height in order to
support the mutual hearing of the musicians and to
avoid simultaneously the generation of disturbing
reflections. According to reference 3, the lower limit of
the ceiling height in musical performance rooms is 5 to
6 m (16 to 19 ft), the upper limit about 13 m (43 ft).
In large rooms for concert performances, the ceiling
configuration should provide clarity-enhancing sound
reflections in the middle and rear audience areas and
simultaneously avoid disturbing reflections via remote
boundary surfaces. Owing to the geometrical reflection,
a plain ceiling arrangement, Fig. 7-30A, supplies only a
slight portion of sound energy to the rear reception area,
but in the front area (strong direct sound), the sound
reflected by the ceiling is not required. In the rear
ceiling area, however, the sound energy is reflected
towards the rear wall from where it is returned,
according to the unfavorable room geometry, as a
disturbing echo (so-called theater echo), to the talker or
the first listener rows. Keeping this in mind, the ceiling
surfaces above the performance zone and in front of the
rear wall should point perpendicular towards the middle
seating area, Figs. 7-30B to D.
Monotonically curved ceilings in the shape of barrel
vaults or cupolas show focusing effects, which in the
neighborhood of such focuses may produce considerable
disturbances in the listener or performer areas. The centerFigure 7-29. Various concert halls.A. Gewandhaus Leipzig, ground plan.D. Philharmonie Berlin, longitudinal section.C. Philharmonie Berlin, ground plan.B. Gewandhaus Leipzig, longitudinal section.