Table 4-8. Transmission LASS (in dB) of Glass Walls or Windows

TM 5-805-4/AFJMAN 3 2 - 1 0 9 0

Table 4-8. Transmission LASS (in dB) of Glass Walls or Windows.

Thickness of Glass (in.)

1/4

3/4

1/2

1/8

Octave

Frequency

Approximate Surface Weight (lb/ft2)

Band

6-1/2

10

1-1/2

3

(Hz)

13

17

2

7

31

19

22

8

14

63

24

26

13

20

125

27

28

19

25

250

29

23

27

500

29

30

27

28

1000

31

32

27

28

2000

36

38

27

31

4000

40

43

31

34

8000

30

31

26

28

STC

Notes :

1. Variations in surface area and edge-clamping conditions can alter the

TL values considerably. There is not much consistency among published data.

2. TL tests usually are not carried out at 31-63 Hz; values given are

estimates only.

In typical operable windows, poor seals can reduce these values.

3.

4. Special laminated safety glass containing one or more viscoelastic

layers sandwiched between glass panels will yield 5-10 dB higher values

than given here for single thicknesses of glass; available in approxi-

mately 1/4- to 3/4-in. thicknesses.

wool blanket of 3- to 4-lb/cu feet density. Around

spaces. The floating floor should not support any

all the perimeter edges of the floating floor (at the

large, heavy operating equipment. Instead, such

walls and around all concrete inertia bases within

equipment should be based on extra-height house-

the floating floor area), there should be l-inch gaps

keeping pads that protrude above the floating

that should later be packed with mastic or fibrous

floor. The floating floor is beneficial, however, in

filling and then sealed with a waterproof nonhar-

reducing transmitted noise from lightweight equip-

dening caulking or sealing material. A curb should

ment and pipe and duct supports. Figure 4-5 offers

be provided around the perimeter of the floated

suggestions on applications and details of floating

slab to prevent water leakage into the sealed

floors.

perimeter joints, and several floor drains should be

(c) Prevention of flanking paths. Figure 4-6

set in the structure slab under the floating slab to

illustrates possible flanking paths (paths 2 and 3)

provide run-off of any water leakage into this

of noise and vibration caused by airborne excita-

cavity space.

tion of walls and columns in the mechanical

(b) Area of floating slab. The floating slab

equipment room. These paths make it impossible

should extend over the full area that needs the

to achieve the low noise levels that the floating

added protection between the noisy and the quiet

floor and resilient ceiling would permit (via path

4-14