Handbook for Sound Engineers

82 Chapter 4

one-half turn at a time. This is continued until an air
space of at least 1 inch is achieved. Fig. 4-28 shows an
alternative raised slab system utilizing springs instead
of neoprene or fiberglass mounts. After the slab is
raised to the desired height, the screw holes are filled
with grout and smoothed. Fig. 4-29 further describes the
elements of the raised-slab system. Turning the screws
in the load-bearing isolation mounts raises the cured
slab, producing an air space of the required height. This
system requires heavier reinforcement rods in the
concrete than the system of Fig. 4-25.

4.3.8 Summary of Floating Floor Systems

Loading must be calculated for each type of floating

floor systems discussed. If the resilient system is too

stiff, vibration will travel through the isolator rendering

it ineffective. Likewise if the springs are too soft, they

will collapse under the weight of the structure and also

be ineffective.

Each floating floor system has its advocates. No one

type of floor will suit all situations. The designer is

urged to consider all the variables before making a deci-

sion. For example, there are pros and cons concerning

use of neoprene versus the compressed, bonded, and

encased units of glass fiber. Most of the arguments have

to do with deterioration of isolating ability with age and

freedom from oxidation, moisture penetration, and so on.

Fig. 4-30 combines several features that have been

discussed in a “room within a room.” The walls are

supported on the floating floor and stabilized with sway

braces properly isolated. The ceiling is supported from

the structure with isolation hangers. This type of hanger

incorporates both a spring, which is particularly good

for isolation from low-frequency vibration, and a

Neoprene or a fiberglass element in series, which

provides good isolation from higher-frequency compo-

nents. An important factor is the application of a

non-hardening type of acoustical sealant at the points

marked “S.” An even better approach would be to

support the ceiling from the walls by using joists or

trusses spanning the room. Such a room should provide

adequate protection from structure-borne vibrations

originating within the building as well as from those

vibrations transmitted through the ground to the building

from nearby truck, surface railroad, or subway sources.

Figure 4-28. Mason Industries FS spring jack up floor
system. Courtesy Mason Industries.

Figure 4-29. Details of a jack mount. Courtesy Mason
Industries.

Figure 4-30. A “room-within-a-room” exemplifying the prin-

ciples discussed in the text.

Hangar—fiberglass

or neoprene

Sway + spring

brace

Double 5/8"

gypsum board Beam

Thermal

building

insulation Floating 4"concrete floor

S SNeoprene or glass fiber mounts s = sealant

S S

S

S

S

S

S