DG 1110.3.120
DESIGN GUIDE: MUSIC AND DRAMA CENTERS
JANUARY 1981
CHAPTER 4: ACOUSTICAL CONSIDERATIONS
PREFERRED NOISE CRITERIA
F I G U R E 4-4.2
TYPICAL MECHANICAL NOISE
FIGURE 4-4.3
CONDITIONS TO BE MITIGATED
equipment can mask speech sounds, making it
tions which may confuse the actor, causing him
difficult or impossible to understand performers.
to slow his speech in order to gain intelligibility.
Intermittent noise is a distracting element that
reduces listening enjoyment.
Music-theater requires the singing actors to have
good aural contact with their accompaniment.
Acousticians have developed standards for pre-
This is usually solved by means of good orches-
ferred background noise level in relation to ac-
tra pit design. When drama or musical-theater
tivities contemplated in a Room. These stand-
is amplified, it is essential that the sound console
ards are referred to as Noise Criteria or NC
operator be located somewhere within the au-
curves. The NC curve specifies permissible am-
dience seating area. Mixing live performance is
a delicate and difficult assignment. It cannot be
bient sound pressure levels at each frequency.
done effectively from a sound booth with or
Time delays are appreciable. Sound waves
without an operable window.
moving through air travel much slower (about
Music listening enjoyment is largely derived
1100 fps) than light. This factor must be consid-
from the relationship between source sound
ered when designing very large Rooms and am-
coming from the musicians' instruments and the
phitheaters. Aural and visual perceptions will be
reflection patterns heard by the listener over a
non-synchronized when the distance between
two to three second period. The perception of
source and listener is too great. Moreover, live
both the source and reflected sound fields are
and artificial sound will be non-synchronized and
related to:
garbled when distributed loudspeakers do not
1. Direction from which sound energy reaches
incorporate adjustments for time delay.
listener.
Aural feedback is needed by performers to as-
2. Amplitude or intensity of sound energy
sess their effectiveness. An acoustically "dead"
each reflection.
house will cause the actor to force his voice in
4. Time intervals between arrival of reflected
an unnatural and perhaps harmful manner. Too
energy signals and direct sound.
live a house will produce excessively late reflec-
4-15
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