Audio Engineering

Acoustic Environment 105

Table 3.4 : Continued

Materials Coeffi cient
125 Hz 250 Hz 500 Hz 1 kHz 2 kHz 4 kHz
Masonite, 1/2 in., mounted over 1-in. air
space

0.12 0.28 0.19 0.18 0.19 0.15

Mineral or glass wool blanket, 1 in., 5–15
lb/ft^2 density mounted against solid
backing
Covered with 5% perforated hardboard
Covered with 10% perforated or 20%
slotted hardboard

0.15

0.10

0.15

0.35

0.35

0.30

0.70

0.85

0.75

0.85

0.85

0.85

0.90

0.35

0.75

0.90

0.15

0.40

Mineral or glass wool blanket, 2 in., 5–15
lb/ft^2 density mounted over
1-in. air space
Covered with open weave fabric
Covered with 10% perforated or 20%
slotted hardboard

0.35

0.40

0.70

0.80

0.90

0.90

0.90

0.85

0.95

0.75

0.90

Openings
Stage, depending on furnishings
Deep balcony, upholstered seats
Grills, ventilating

0.25–0.75
0.50–1.00
0.15–0.50
Plaster, gypsum or lime
Smooth fi nish, on tile or brick
Rough fi nish on lath
Smooth fi nish on lath

0.013

0.02

0.02

0.015

0.03

0.02

0.02

0.04

0.03

0.03

0.05

0.04

0.04

0.04

0.04

0.05
0.03
0.03
Plywood panels
2 in., glued to 2 ½ -in. thick plaster wall
on metal lath
1/4 in., mounted over 3-in. air space,
with 1-in. glassfi ber batts right behind
the panel
3/8 in.

0.05

0.60

0.28

0.30

0.22

0.05

0.10

0.17

0.09

0.09

0.02

0.09

0.10

0.09

0.11
Rockwool blanket, 2-in. thick batt
(Semi-Thik)
Mounted against solid backing
Mounted over 1-in. air space
Mounted over 2-in. air space

0.34

0.36

0.31

0.52

0.62

0.70

0.94

0.99

0.99

0.83

0.92

0.98

0.81

0.92

0.92

0.69

0.86

0.84

(Continued)