Page 252 - Master Handbook of Acoustics

Glass-fiber insulation commonly comes with a Kraft paper backing. Between walls, this paper has
no significant acoustical effect, but if building insulation is used as a sound absorber on walls,

perhaps behind a fabric facing, the paper becomes significant. Figure 12-8 compares the sound
absorption efficiency of R-19 (6-in) and R-11 (3.5-in) glass fiber with the Kraft paper backing
exposed, and with the glass fiber exposed to the incident sound. When the paper is exposed, it shields
the glass fiber from sound above 500 Hz but has little effect below 500 Hz. The net effect is an
absorption peak at 250 Hz (R-19) and 500 Hz (R-11), which may be important in room treatment.
With insulation exposed, there is essentially perfect absorption above 250 Hz (R-19) or 500 Hz (R-
11).