o_18tibebsk1upb80q14ejo8p12eva.pdf

industry has used more creative designs in the
past few years that employ "mass-air-mass"
combinations to achieve higher performance
with a Hghter-weight wall with decreased
dimensions.
"I think that [space] is first and foremost,"
Barath says, "because obviously that means
real estate we're giving up, and it means seats
that we're giving up, if we have very thick,
massive walls. What one does now is have
walls that are tailored specifically for the use of
digital soundtracks—walls that will give us an
acceptable amount of Transmission Loss [TL]
and enough attenuation between auditoriums to
meet a desirable standard for this industry."
The typical solution for solving sound lealage between screening rooms has been
to utilize tlie "more mass' theory. Although it is effective, the wall width necessary
to stop today's digital sound range decreases seating space so dramatically that it
is impractical for modern theater owners.
FIGURE 1: "No mas" for the more-mass theory.
Doggett, owner of Philadelphia-based MetropoUtan
Acoustics, specializes in providing
sound solutions. Like Baratii, she emphasizes
looking at TL values when constructing walls.
Doggett suggests that an exhibitor begin with
three goals in mind:
• Decide what level of sound isolation (the
TL factor) will be the acceptable standard
between individual theaters;
• Accept only an extremely low reverberation
time inside each theatre; and
• Select a mechanical system (heating and
cooUng) with very low background noise.
Doggett says that a combination of materials
with air space is the solution, as that can
stop low frequency noise as weU as a more
massive concrete wall. "It's best to use some
air space so there's not a connection between
the two sides of die wall. When the sound does
come through one side, then it's not a total
connection to the other side."
Both Barath and Doggett suggest, in addition
to using air space to help minimize sound
leakage, using combinations ofbuilding materials,
such as furred-out drywall, stud walls
with resihent clips, gypsum board, insulation,
and composite materials. All elements depend
on the sound control standards desired and the
specific needs of the facility. "Using layers of
materials will also help attenuate resonant frequencies,"
Doggett says. "Each material has a
frequency that sound comes through best. So,
if you use different materials, you're catching
a lot of those resonant frequencies."
Barath suggests also using a Noise Criterion
(NC) value to determine the efficiency of
an auditorium. The NC rating can be determined
by an acoustics/engineering designer to
decide how best to mitigate internal ambient
noise and external intrusive noise. Considering
TL, NC and Sound Transmission Class (STC)
values is certainly essential, but every structure
is unique. The final answer, Holman says, depends
on the locale. Building material prices
can vary widely, and local weather and altitude
considerations will also affect the design, as will
county, state and national building regulations.
Of course, a certain amount of sound leakage
might be acceptable, depending upon how
stringent an exhibitor wants to be. To achieve
the best answers for each specific situation, it
is important that a theatre
owner communicate
with the architect, acoustician,
design engineer
and construction firm
and make sure they are
all woridng together to
airive at the best sound
solutions.
The bottom line is
this : The high quaUty the
pubhc has come to expect
will determine
what's acceptable and
what's not. Today, their
sound systems at home,
and even in their cars,
are
of extremely high
quaUty. Exhibitors seek-
ingprofitabilitymustde-
mand a new standard that is, Barath says, "at
least commensurate or better than what the
majority of these moviegoers would experience
in their own environments."
Hi
With a dozen years ofconstruction industry
experience (the last two spent in Troy Walls'
research and de\'elopment area), Bill Bergiadis
developed the design used in Troy Sound Wall
Systems, which
Bill Bergiadis
consist of superefficient
wall materials
that allow
maximum sound
dampening (an
STC rating of 68,
exceeding even
THX criteria) with
minimal space
usage. By condensing
standard
wall mass, incorporating
limp
mass within the design,
Troy walls
provide the highest transmission loss values
with minimum dimensions. Based in Commerce,
Calif, Troy can be reached at 800-987-
3306 or 213-838-3676 Janis Hunt Johnson is
Managing Editor of Ask Janis Editorial &
Rewrite Services. The authors wish to thank
Jim Barath, Michelle Branton Koks, V. Wade
Contreras, Felicia Doggett, Tom Holman,
David C. Johnson and Cal Leaning for their
expert assistance in this article's preparation.
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