Page 200 - The Master Handbook Of Acoustics

175
CONTROL OF INTERFERING NOISE

Prefabricated double glass windows are available commercially,
one of which is rated at STC 49 dB.

Sound-Insulating Doors

The transmission loss of a door is determined by its mass, stiffness,
and air-tightness. An ordinary household panel door hung in the usual
way might offer less than 20 dB sound insulation. Increasing the
weight and taking reasonable precautions on seals might gain another
10 dB, but a door to match a 50 dB wall requires great care in design,
construction, and maintenance. Steel doors or patented acoustical
doors giving specified values of transmis-
sion loss are available commercially but
they are quite expensive. To avoid the
expense of doors having high transmission
loss, sound locks are commonly used.
These small vestibules with two doors of
medium transmission loss are very effec-
tive and convenient.
Doors with good insulating properties
can be constructed if the requirements of
mass, stiffness, and airtightness are met. 5 /8" Gypsum bd.
Figure 8-10 suggests one inexpensive 2 6
approach to the mass requirement, filling a 2 4
3
hollow door with sand. Heavy plywood ( ⁄4
in) is used for the door panels.
Achieving a good seal around a “sound- 16"
proof” door can be very difficult. Great
force is necessary to seal a heavy door.
Wear and tear on pliant sealing strips can Construction - Staggered stud partition
destroy their effectiveness, especially at
Weight - 7.2 lb/sq ft
the floor where foot-wear is a problem.
The detail of Fig. 8-10 shows one approach Sound transmission class
STC 42 dB without fiberglass
to the sound leakage problem in which a STC 46 to 52 dB with fiberglass
very absorbent edge built around the
(Owens-Corning Fiberglas Corporation)
periphery of the door serves as a trap for
sound traversing the crack between door FIGURE 8-7
and jamb. This absorbent trap could also Staggered stud partition.