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.
. 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.
|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