Appendix K — Sound Absorption Coefficients Table 8.K.1: Sound Absorption Coefficients a

Source: Stein, B. et al., 2006. Mechanical and Electrical Equipment for Buildings. John Wiley & Sons, New Jersey Absorption Coefficients (α) 500 1000 2000 4000 NRCc 125 Hz250 Hz General Building Materials and Furnishings b Hz Hz Hz Hz

Brick, unglazed                                           0.03   0.03   0.03    0.04      0.05   0.07 0.005
                                                                                                        5
Brick, unglazed, painted                                  0.01   0.01   0.02    0.02      0.02   0.03 0.00

Carpet, heavy, on concrete                                0.02   0.06   0.14    0.37      0.60   0.65   0.29

Carpet, heavy, on 1.36 kg/m2 hair felt or foam rubber     0.08   0.24   0.57    0.69      0.71   0.73   0.55

Concrete block, coarse                                    0.36   0.44   0.31    0.29      0.39   0.25   0.35

Concrete block, painted                                   0.10   0.05   0.06    0.07      0.09   0.08   0.05

Fabrics

Light velour, 0.34 kg/m2, hung straight, in contact with 0.03    0.04 0.015 0.17          0.24   0.35   0.15
wall
Medium velour, 0.47 kg/m2, draped to half area           0.07    0.31   0.49    0.75      0.70   0.60   0.55

Heavy velour, 0.61 kg/m2, draped to half area             0.14   0.35   0.55    0.72      0.70   0.65   0.60

Floors

Concrete or terrazzo                                      0.01   0.01 0.015 0.02          0.02   0.02   0.00

Linoleum, asphalt, rubber, or cork tile on concrete       0.02   0.03   0.03    0.03      0.03   0.02   0.05

Wood                                                      0.15   0.11   0.10    0.07      0.06   0.07   0.10

Glass

Large panes of heavy plate glass                          0.18   0.06   0.04    0.03      0.02   0.02   0.05

Ordinary window glass                                     0.35   0.25   0.18    0.12      0.07   0.04   0.15

Gypsum board, 13 mm nailed to 50x100 mm stud 400 0.10            0.08   0.05    0.03      0.03   0.03   0.05
mm c/c
Marble or glazed tile                                     0.01   0.01   0.01    0.01      0.02   0.02   0.00

Openings
Stage, depending on furnishings                                               0.25-0.75
Deep balcony, upholstered seats                                               0.50-1.00
Grillese ventilating                                                          0.15-0.50

                                                                      Absorption Coefficients (α)
General Building Materials and Furnishings b                 125    250    500    1000 2000 4000 NRCc
                                                             Hz     Hz     Hz      Hz   Hz   Hz
Plaster, gypsum or lime, smooth finish on tile or brick 0.013 0.015 0.02          0.03   0.04   0.05   0.05

Plaster, gypsum or lime, on lath 0.14 0.10 0.06 0.05 0.04 0.03 0.05

Plywood panelling, 9 mm thick                                0.28   0.22   0.17   0.09   0.10   0.11   0.15
Rough wood, as tongue-and-groove cedar                       0.24   0.19   0.14   0.08   0.13   0.10   0.14
Slightly vibrating surface (e.g., hollow core door)          0.02   0.02   0.03   0.03   0.04   0.05   0.03
Readily vibrating surface (e.g., thin wood panelling on      0.10   0.07   0.05   0.04   0.04   0.05   0.05
400 mm studs)
Water surface, as in swimming pool                           0.008 0.008 0.013 0.015 0.020 0.025 0.00

 Absorption of Seats and Audience d                          125    250    500    1000 2000 4000 NRCc
                                                             Hz     Hz     Hz      Hz   Hz   Hz
Audience, in upholstered seats, per 0.093 m2 of floor        0.60   0.74   0.88   0.96   0.93   0.85    -
area
Unoccupied cloth-upholstered seats, per 0.093 m2 of          0.49   0.66   0.80   0.88   0.82   0.70    -
floor area
Wooden pews, occupied, per 0.093 m2 of floor area            0.57   0.61   0.75   0.86   0.91   0.86    -

Students in tablet-arm chairs, per 0.093 m2 of floor         0.30   0.42   0.50   0.85   0.85   0.84    -
area
                                                             125    250    500    1000 2000 4000
 Acoustic Absorptive Materials                        Mtge   Hz     Hz     Hz      Hz   Hz   Hz NRC
                                                                                                   c

High-performance vinyl-faced fibreglass
Ceiling panels
25 mm thick                                           E405 0.73     0.88   0.71   0.98   0.96   0.77   0.90
38 mm thick                                           E405 0.79     0.98   0.83   1.03   0.98   0.80   0.95
Painted nubby glass cloth panels
6 mm thick                                            E405 0.81     0.94   0.65   0.87   1.00   0.96   0.85
25 mm thick                                           E405 0.78     0.92   0.79   1.00   1.03   1.10   0.95

Random fissured 19 mm-thick panels                    E405 0.52     0.58   0.60   0.80   0.92   0.80   0.70
Perforated metal panel with infill 1 in. thick        E405 0.70     0.86   0.74   0.88   0.95   0.86   0.85
Typical averages, mineral fibre tiles and panels

19 mm fissured                                        E405 0.47     0.50   0.52   0.76   0.86   0.81   0.65

19 mm textured                                        E405 0.49     0.55   0.53   0.80   0.94   0.83   0.70
   16 mm fissured                                     E405 0.28     0.33   0.66   0.73   0.74   0.75   0.60

16 mm textured                                     E405 0.29     0.35   0.66   0.63   0.44   0.34   0.50

16 mm perforated                                   E405 0.27     0.29   0.55   0.78   0.69   0.53   0.60

75 mm in thick x 400 mm square on 600 mm A 0.40 0.61 1.92 2.54 2.62 2.60 centres

a This table primarily useful for preliminary calculations. Complete tables of coefficients may be found in books on architectural acoustics. b Selected data courtesy of Owens-Corning Fibreglass. c NRC: the arithmetic average of the α values at 250, 500, 1000, and 2000 Hz. d If audience is randomly spaced, use an average or 0.47 m2 sabins per person. e See figure at right for mounting methods Type A and Type E 405.