Handbook for Sound Engineers

78 Chapter 4

of the engineering and calculations that have been
discussed so far can be rendered meaningless if suffi-
cient care is not taken to seal all holes in a partition.

4.3.6 Floor and Ceiling Construction

Building high TL walls around a sound room is futile

unless similar attention is given to both the floor/ceiling

system above the room and to the floor of the sound

room itself. Heel and other impact noise on the floor

above the room is readily transmitted through the

ceiling structure and radiated into the sound room

unless precautions are taken. The floor and ceiling

structure of Fig. 4-18A is the type common in most

existing frame buildings. Impact noise produced on the

floor above is transmitted through the joists to the

ceiling diaphragm below and radiated with little loss

into the room below. Carpet on the floor above softens

heel taps, but is low mass, and therefore has little effect

on transmission of structure-borne sounds. Some decou-

pling of the floor membrane from the ceiling membrane

is introduced in Fig. 4-18B in the form of resilient

mounting of the ceiling gypsum board. Placing absor-

bent material in the cavity is also of modest benefit. In

Table 4-8 four floor and ceiling structures are described

along with STC ratings for each, as determined from

field TL measurements.

Figure 4-16. Caulking methods used for partitions.

Figure 4-17. Effect of gaps on transmission loss. Courtesy
of Russ Berger, Russ Berger Designs.

Wood plate

Caulk

A. Wood plate

Rough

concrete slab

Steel

runner track

Caulk

B. Steel runner track

40

35

30

25

20

15

(^10101520253035404550)
(13)
(17)
(20)
(23)
(27)
(30)
(33)
(37)
(40)
Effective transmission loss of wall with openings—dBTransmission loss of wall with no openings—dB
0.02% Open
0.05% Open
0.1% Open
0.2% Open
0.5% Open
1% Open
2% Open
5% Open
0.01% Open
No Leakage
Figure 4-18. Floor and ceiling systems.
A. Commonly found construction that passes
impact noise from the floor above to the one
below with little loss.
B. Similar system having greatly increased
transmission loss resulting from the suspension
of the ceiling on resilient channels and an
absorbent introduced into the air space.