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auditorium presented the greatest challenge, as every change in
its structure affected the acoustics and, potentially, a range of
architecturally important features. The goal was to treat the auditorium
as a rigid box that would communicate its strength to the rest of
the building. To achieve this, nine thousand cubic feet of reinforced
concrete were added. New spaces then had to be found to compensate
for the loss of volume. The projection booth was pushed back five
feet, and an acoustic cove (around the coffered ceiling) and gallery
were added. Clerestory openings replace windows that were blocked
off in the 1984 restoration.
McKay was the acoustician on both occasions, and he seized the opportunity
to introduce more radical changes than he had been able to before.
"For sound, a flat surface is like a mirror reflecting light --
it produces glare,” he explains, pointing out the three thicknesses
of terra-cotta blocks on the side walls and the pillow-like modeling
of the proscenium arch, all of which now serve to scatter the sound
waves. Ten different fabrics were considered for the new seats before
finding one that was transparent to sound, and the carpet was replaced
by a resonant hardwood floor.
most crucial changes took place in the region high above the heads
of the audience. The challenge was to achieve a reverberation time
that could be shortened for the spoken word and lengthened for musical
performances. For speech, gold cloth banners are lowered around
three sides of the ceiling cove, and hinged fabric-covered screens
fold out in the gallery; these absorbent surfaces cut the reverberation
time to 1.25 seconds. To lengthen the reverberation to two seconds,
the banners and screens are withdrawn, allowing the music to resonate.
There is also a demountable orchestra enclosure that contains and
directs the sound of a musical group, preventing it from being dispersed
within the stage tower.