Handbook for Sound Engineers

80 Chapter 4

raises it only to STC-59. There are many recording
studios and other sound-sensitive rooms that require
floors greater than STC-54. The answer is in dividing
available mass and placing an air space between. The
results of an actual test, sponsored by Mason Indus-
tries, Inc., are given in Fig. 4-21.^12 The TL of basic T
sections (4 inch floor thickness) with 2 inches of poured
concrete gives a total thickness of 6 inches and the
STC-54 mentioned previously. Adding a 4 inch
concrete floor on top of the same structural floor with
1 inch of air gap gives a healthy STC-76, which should
be adequate for all but the most critical applications. A
4 inch slab added to the 6 inch floor without an air
space gives only STC-57. A 19 dB improvement can be
attributed directly to the air space.

Continuous Underlayment. The continuous underlay-

ment is the simplest and easiest form of floating floor to

construct. It is most often used for residential and light

commercial applications where surface loads are rela-

tively light. The technique consists of laying down

some sort of vibration-absorbing mat andthen

constructing a floor on top of the mat, taking care not to

penetrate the mat with any fasteners. The perimeter is

surrounded with a perimeter isolation product and

sealed with a nonhardening acoustical sealant. Maxxon

offers a number of products including Acouti-Mat 3,

Acousti-MatII-Green, and Enkasonic®. These are all

underlayments that form a resilient layer upon which a

wood floor can be constructed, Fig. 4-22, or can be part

of a poured concrete system.

Isolation Mount Systems. If heavier loads are antici-

pated and greater isolation is needed, an isolation mount

system should be considered. Various manufacturers

build systems for isolating either wood floors or

concrete slabs. Wood floors can be isolated as shown in

Fig. 4-23. This system offered by Kinetics utilizes

encapsulated fiberglass pads, imbedded in a roll of

low-frequency fiberglass designed to fill the air space.

Figure 4-21. Four methods used in floating floors for
increasing transmission loss.

A. Continuous underlayment

B. Isolation mount system

C. Raised-slab system utilizing

neoprene for resiliency

D. Raised-slab system utilizing

springs for resiliency

Figure 4-22. Enkasonic floor system.

Figure 4-23. Kinetics Floating Wood Floor. Courtesy

Kinetics Corp.