DG 1110.3.120
DESIGN GUIDE: MUSIC AND DRAMA CENTERS
JANUARY 1981
CHAPTER 4: ELECTRONIC SYSTEMS
be remembered that no matter what mecha-
nisms intervene, people hear with their ears, nat-
signing a volume-per-seat factor. This is clearly
urally, and impart an innate organization and
limited in application to the "typical" Rooms de-
sensitivity to the process. Second, there may be
fined. A Surround music hall, for instance, re-
a tendency for design professionals and non-de-
quires a considerably higher volume-per-seat
signers alike to assume the existence of equip-
factor.
ment that will "fix" malfunctions brought about
by lack of attention to and understanding of
Decibels are not a direct measure of loudness,
acoustic principles; this is usually false, and the
but of the difference in the level of two amounts
misunderstanding can be a costly one. Finally,
of power-namely, 10 times the logarithm of the
many of the functional criteria and conditions for
ratio. By international agreement, the reference
good listening apply no matter what means is
sound intensity of human hearing is 10 16 watts
employed for generating sound to be listened to.
per square centimeter. With that as zero decibels,
Electronic audio systems simply introduce a few
the range extends to 120 decibels, the threshold
more steps in the signal path.
of discomfort. Decibels measure the energy in
a pressure wave. Loudness is a subjective eval-
Audio systems have four parts in common: Input
uation. A 10db increase doubles apparent loud-
transducer (microphone, tape head, phono car-
ness, 20db quadruples, etc.
tridge), signal processor (tuning, filters, mixing,
volume, delay), amplifier, and output transducer
Musicians use their own vocabulary to describe
(loudspeaker). Signal processing accounts for
the qualitative aspects of musical sound. It is the
major differences in application.
role of the acoustician to identify the physical
acoustic criteria associated with each subjective
parameter and translate these terms into useful
tem's purpose is to increase the reverberation
architectural concepts.
time of a Room by introducing very small delays
The accompanying charts and diagrams will help
between the input and output by way of a digital
define the empirical basis and physical impli-
processor. It may have one or more predeter-
cations of acoustical properties. Section 4-6 in-
mined settings appropriate to various Room
cludes sample construction details indicative of
uses. Ideally, it will not alter the characteristic
requirements for noise control.
frequency response spectrum of a well-designed
auditorium or provide acoustic gain (increased
loudness). But in cases where a portion of the
4-5. ELECTRONIC SYSTEMS
spectrum drops out of reverberant field, the pro-
cessor can selectively strengthen that part.
This corrective function (called equalization) can
be useful when it is desirable to shorten natural
A. COMMENTARY
reverberation time by adding absorptive mate-
rial to the volume; the material tends to absorb
This Design Guide has tended to emphasize nat-
certain frequencies more than others.
ural acoustics for three reasons. First, it should
4-18
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