Audio Engineering

850 Chapter 29

Table 29.3 : Typical Sound Absorption Coeffi cients

Hz

Material 125 250 500 IK 2K 4K

Drapes 0.07 0.37 0.49 0.31 0.65 0.54

● Light velour 0.07 0.31 0.49 0.75 0.70 0.60

● Medium velour 0.07 0.35 0.55 0.72 0.70 0.65

● Heavy velour 0.14 0.35 0.55 0.72 0.70 0.65

Carpet

● Heavy on concrete 0.02 0.06 0.14 0.37 0.60 0.65

● Heavy on underlay or felt 0.08 0.24 0.57 0.70 0.70 0.73

● Thin 0.01 0.05 0.10 0.20 0.45 0.65

Cork fl oor tiles and linoleum,

plastic fl ooring

0.02 0.04 0.05 0.05 0.10 0.05

Glass (windows)

● 4 mm 0.30 0.20 0.10 0.07 0.05 0.02

● 6 mm 0.10 0.08 0.04 0.03 0.02 0.02

Glass, tile, and marble 0.01 0.01 0.01 0.01 0.02 0.02

Glass fi ber mat

● 80 kg/m^3 –25 mm 0.10 0.30 0.55 0.65 0.75 0.80

● 80 kg/m^3 –50 mm 0.20 0.45 0.70 0.80 0.80 0.80

Wood fi ber ceiling tile 0.15 0.40 0.70 0.80 0.80 0.80

Plasterboard over deep airspace 0.20 0.15 0.10 0.05 0.05 0.05

Typically, such a partition might achieve the following insulation values:

Frequency (Hz) 63 125 250 500 1K 2K 4K

Insulation (dB) 40 50 60 65 70 75 80

However, the fi nal value will very much depend on the quality of the construction and
also on the presence of fl anking transmission paths, that is, other sound paths, such as
ducting or trunking runs, that short circuit or bypass the main barrier.