Introduction to Acoustics

344 Part C Architectural Acoustics
Part C 9.7
Built 1986
Drama
V = 5000m 3
T = 1.1s
Opera
V = 6000m 3
T = 1.3s
Concert
V = 9000m 3
T = 1.8s
Fig. 9.53 The Idun multipurpose hall in Umeå, Sweden, with variable volume and stage configurations. The hall seats
up to 860 people. Brief data (left), photos from cardboard model, long section and plan (right)
Still, a few examples of such successful designs exist.
The most innovative is probably the Segerstrom Hall
in Orange County, California, USA, which is shown
in Fig. 9.54. This hall features a special layout of the
almost 3000 audience seats, which are distributed on
four levels. Each of these forms an almost rectangular,
or even reverse fan, shape. However, the orientation of
each level is shifted so that the overall plan becomes
a wide fan. In this way the virtues of the fan shape for
audience proximity to the stage are combined with the
advantages of the rectangular shape for strong, early
reflections from lateral directions. Thus, although the
total width is about 50 m, the lateral energy level in this
hall resembles that found in rectangular, 25 m-wide concert
halls with typical seating capacity up to, say, 2000
people [9.36].
9.7.5 Halls for Rhythmic Music
Halls intended for rhythmic, amplified music concerts
range in size from less than 100 to perhaps more than
50 000 listeners (in roofed sports arenas). The reason for
this broad range of audience capacity is that the size and
number of the sound amplification loudspeakers as well
as of event video screens can be chosen at will to ensure
good vision and adequate (often too high) sound levels
for any size of audience. In any case, the reverberation
time should be close to the optimal for speech, i. e., not
more than 1 s if possible.
In huge arenas, of course, the reverberation time
will be higher; but if efficient absorption is applied to
the critical surfaces, a higher reverberation time need
not compromise clarity. This is because the reverber-