Handbook for Sound Engineers

106 Chapter 5

surface area tends to increase it. Figs. 5-13 and 5-14
provide absorption coefficients for different patterns of
foam and different thicknesses of foam of the same
pattern, respectively, for acoustical foam panels available
from Auralex Acoustics, Inc.^19

In general, acoustical foams are of lower density than
fibrous materials; acoustical foam densities are generally
in the 8.0 to 40 kg/m³ (0.5 to 2.5 lb/ft³) range. This
means that mineral fiber panels tend to provide higher
absorption coefficients than foam panels of the same
thickness. However, acoustical foams can generally be
installed without any decorative covering, which can
make them more cost-effective—mineral fiber panels
tend to require a fabric finish, or some other cover to
contain airborne fibers. Melamine foams, such as the
acoustical products offered by Pinta Acoustic, Inc.

(formerly Illbruck) are white in color and have a higher

resistance to fire relative to polyurethane foams.

However, melamine foams generally have lower absorp-

tion coefficients (largely due to lower densities) and tend

to be less flexible, making them more prone to damage

than polyurethane foams. A sampling of the acoustical

performance of some melamine foam products available

from Pinta Acoustic, Inc. is provided in Fig. 5-15.^20

Melamine foams may be painted (the manufacturer

should always be consulted about this), while polyure-

thane foams should generally not be painted. Because of

this, companies offering polyurethane foams generally

have a wider variety of colors available.

Figure 5-12. Open cell polyurethane acoustical foam.

Figure 5-13. The effect of shape on the absorption of
Auralex Acoustics polyurethane foam panels of 5.1 cm
(2 in) thickness, Type A mounting.^19

125 250 500 1k 2k 4k

1.40

1.20

1.00

0.80

0.60

0.40

0.20

0.00

Octave band center frequency—Hz

ASAB

Wedges

Pyramids

Square-cut

(Metro)

“Egg-carton”

Sonomatt)

Flat panel

(SonoFlat)

Figure 5-14. The effect of thickness on the absorption of

Auralex Acoustics Studiofoam Wedges, Type A mounting.^19

Figure 5-15. The absorption of Pinta Acoustic melamine

foam panels of different thicknesses, Type A mountings.^20

125 250 500 1k 2k 4k

1.40

1.20

1.00

0.80

0.60

0.40

0.20

0.00

Octave band center frequency—Hz

ASAB

2.5 cm (1 in)

5.1 cm (2 in)

7.6 cm (3 in)

10.2 cm (4 in)

125 250 500 1k 2k 4k

1.40

1.20

1.00

0.80

0.60

0.40

0.20

0.00

Octave band center frequency—Hz

ASAB SONEXmini

2.5 cm (1 in)

SONEXmini

3.8 cm (1.5 in)

SONEXclassic

5.1 cm (2 in)

SONEXone

7.6 cm (3 in)