Page 239 - The Master Handbook Of Acoustics
P. 239

214   CHAPTER NINE





                                          1.2
                                      A
                                          1.0
                                                                        Insulation toward sound
                                          0.8

                                          0.6                        Kraft paper toward sound
                                                          R-19
                                          0.4

                                          0.2
                                         Absorption coefficient  1.2 125  250  500 Frequency - Hz  2 kHz  4 kHz

                                           0
                                                                           1 kHz





                                          1.0
                                                                           Insulation toward sound
                                          0.8

                                          0.6                               Kraft p aper toward sound
                                                                R-11
                                          0.4

                                          0.2


                                      B    0
                                            125        250       500       1 kHz      2 kHz     4 kHz
                                                                   Frequency - Hz
                                     FIGURE 9-29
                                    When ordinary building insulation is used as a wall treatment (perhaps with fabric fac-
                                    ing) the position of the kraft paper backing becomes important. (A) R-19 Fiberglass
                                    building insulation, (B) R-11 Fiberglass building insulation, Mounting A.

                                   room treatment. With insulation exposed there is essentially perfect
                                   absorption above 250 Hz (R-19) or 500 Hz (R-11).
                                      Building insulation has not caught on as an inexpensive absorbing
                                   material. One reason is that some sort of cosmetic and protective cover
                                   is required, but this is often true of denser materials as well. Fabric,
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