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| COMMUNICATION CENTERS |
Communication centers include telephone terminal buildings,
radio stations, television studios, and transmitter and receiver
stations.
Most telephone terminal rooms are air conditioned because
constant temperature and relative humidity help prevent breakdowns
and increase equipment life. In addition, air conditioning
permits the use of a lower number of air changes, which, for
a given
filter efficiency, decreases the chances of damage to relay
contacts
and other delicate equipment.
Radio and television studios require critical analysis for
the elimination
of heat buildup and the control of noise. Television studios
have the added problem of air movement, lighting, and occupancy
load variations. This section deals with television studios
because
they present most of the problems also found in radio studios.
Load Characteristics
Human occupancy is limited, so the air-conditioning load for
telephone terminal rooms is primarily equipment heat load.
Television studios have very high lighting capacities, and
the
lighting load may fluctuate considerably in intensity over
short periods.
The operating hours may vary every day. In addition, there
may
be from one to several dozen people onstage for short times.
The airconditioning
system must be extremely flexible and capable of handling
wide load variations quickly, accurately, and efficiently,
similar
to the conditions of a theater stage. The studio may also
have an
assembly area with a large number of spectator seats. Generally,
studios
are located so that they are completely shielded from external
noise and thermal environments.
Design Concepts
The critical areas of a television studio are the performance
studio
and control rooms. The audience area may be treated much like
a place of assembly. Each area should have its own air distribution
system or at least its own zone control separate from the
studio system.
The heat generated in the studio area should not be allowed
to
permeate the audience atmosphere.
The air distribution system selected must have the capabilities
of
a dual-duct, single-duct system with cooling and heating booster
coils, a variable air volume systems, or a multizone system
to satisfy
design criteria. The air distribution system should be designed
so
that simultaneous heating and cooling cannot occur unless
heating
is achieved solely by heat recovery.
Studio loads seldom exceed 350 kW of refrigeration. Even if
the
studio is part of a large communications center or building,
the studio
should have its own refrigeration system in case of emergencies.
The refrigeration equipment in this size range may be reciprocating
units, which require a remote location so that machine noise
is isolated
from the studio.
Special Considerations
On-Camera Studios. This is the stage of the television studio
and requires the same general considerations as a concert
hall
stage. Air movement must be uniform, and, because scenery,
cameras,
and equipment may be moved during the performance, ductwork
must be planned carefully to avoid interference with proper
studio operation.
Control Rooms. Each studio may have one or more control
rooms serving different functions. The video control room,
which
is occupied by the program and technical directors, contains
monitors
and picture-effect controls. The room may require up to 30
air
changes per hour to maintain proper conditions. The large
number
of necessary air changes and the low sound level that must
be maintained
require special analysis of the air distribution system.
If a separate control room is furnished for the announcer,
the heat
load and air distribution problems will not be as critical
as those for
control rooms for the program, technical, and audio directors.
Thermostatic control should be furnished in each control room,
and provisions should be made to enable occupants to turn
the air
conditioning on and off.
Noise Control. Studio microphones are moved throughout the
studio during a performance, and they may be moved past or
set
near air outlets or returns. These microphones are considerably
more sensitive than the human ear; therefore, air outlets
or returns
should be located away from areas where microphones are likely
to
be used. Even a leaky pneumatic thermostat can be a problem.
Air Movement. It is essential that air movement within the
stage area, which often contains scenery and people, be kept
below 0.13 m/s within 3.7 m of the floor. The scenery is often
fragile
and will move in air velocities above 0.13 m/s; also, actors’
hair
and clothing may be disturbed.
Air Distribution. Ductwork must be fabricated and installed
so
that there are no rough edges, poor turns, or improperly installed
dampers to cause turbulence and eddy currents within the ducts.
Ductwork should contain no holes or openings that might create
whistles. Air outlet locations and the distribution pattern
must be
carefully analyzed to eliminate turbulence and eddy currents
within
the studio that might cause noise that could be picked up
by studio
microphones.
At least some portions of supply, return, and exhaust ductwork
will require acoustical material to maintain noise criterion
(NC)
levels from 20 to 25. Any duct serving more than one room
should
acoustically separate each room by means of a sound trap.
All ductwork
should be suspended by means of neoprene or rubber in
shear-type vibration mountings. Where ductwork goes through
wall or floor slabs, the openings should be sealed with acoustically
deadening material. The supply fan discharge and the return
and
exhaust fan inlets should have sound traps; all ductwork connections
to fans should be made with nonmetallic, flexible material.
Air outlet locations should be coordinated with ceiling-mounted
tracks and equipment. Air distribution for control rooms may
require a perforated ceiling outlet or return air plenum system.
Piping Distribution. All piping within the studio, as well
as in
adjacent areas that might transmit noise to the studio, should
be supported
by suitable vibration isolation hangers. To prevent transmission
of vibration, piping should be supported from rigid structural
elements to maximize absorption.
Mechanical Equipment Rooms. These rooms should be
located as remotely from the studio as possible. All equipment
should be selected for very quiet operation and should be
mounted
on suitable vibration-eliminating supports. Structural separation
of
these rooms from the studio is generally required.
Offices and Dressing Rooms. The functions of these rooms are
quite different from each other and from the studio areas.
It is recommended
that such rooms be treated as separate zones, with their
own controls.
Air Return. Whenever practicable, the largest portion of studio
air should be returned over the banks of lights. This is similar
to theater
stage practice. Sufficient air should also be removed from
studio
high points to prevent heat buildup. |
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