THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

250 11. Acoustics of Enclosed Spaces: Architectural AcousticsTable 11.1. Absorption Coefficients.Octave-Band Center Frequency (Hz)125 250 500 1000 2000 4000Brick, unglazed 0.03 0.03 0.03 0.04 0.05 0.07Brick, unglazed, painted 0.01 0.01 0.02 0.02 0.02 0.03Carpet on foam rubber 0.08 0.24 0.57 0.69 0.71 0.73Carpet on concrete 0.02 0.06 0.14 0.37 0.60 0.65Concrete block, coarse 0.36 0.44 0.31 0.29 0.39 0.25Concrete block, painted 0.10 0.05 0.06 0.07 0.09 0.08Floors, concrete or terrazzo 0.01 0.01 0.015 0.02 0.02 0.02Floors, resilient flooring 0.02 0.03 0.03 0.03 0.03 0.02on concreteFloors, hardwood 0.15 0.11 0.10 0.07 0.06 0.07Glass, heavy plate 0.18 0.06 0.04 0.03 0.02 0.02Glass, standard window 0.35 0.25 0.18 0.12 0.07 0.04Gypsum, board 0.5 in. 0.29 0.10 0.05 0.04 0.07 0.09Panels, fiberglass, 1.5 in. thick 0.86 0.91 0.80 0.89 0.62 0.47Panels, perforated metal, 4 in. thick 0.70 0.99 0.99 0.99 0.94 0.83Panels, perforated metal with 0.21 0.87 1.52 1.37 1.34 1.22fiberglass insulation, 2 in. thickPanels, perforated metal with 0.89 1.20 1.16 1.09 1.01 1.03mineral fiber insulation, 4 in. thickPanels, plywood, 3/8 in. 0.28 0.22 0.17 0.09 0.10 0.11Plaster, gypsum or lime, rough 0.02 0.03 0.04 0.05 0.04 0.03finish on lathPlaster, gypsum or lime, smooth 0.02 0.02 0.03 0.04 0.04 0.03finish on lathPolyurethane foam, 1 in. thick 0.16 0.25 0.45 0.84 0.97 0.87Tile, ceiling, mineral fiber 0.18 0.45 0.81 0.97 0.93 0.82Tile, marble or glazed 0.01 0.01 0.01 0.01 0.02 0.02Wood, solid, 2 in. thick 0.01 0.05 0.05 0.04 0.04 0.04Water surface nil nil nil 0.003 0.007 0.02One person 0.18 0.4 0.46 0.46 0.51 0.46Air nil nil nil 0.003 0.007 0.03Note: The coefficient of absorption for one person is that for a seated person (m 2 basis). Air absorptionis on a per cubic meter basis.are for “random” incidence as distinguished from “normal” or “perpendicular”incidence.The angle–absorption correlation appears to be of somewhat erratic nature,but at high frequencies the absorption coefficients in some materials is roughlyconstant at all angles. At low frequencies the random-incidence absorption tendsto be greater than for normal incidence. However, as Table 11.1 shows, α variesconsiderably with frequency for many materials, and the absorption coefficientsare generally measured at six standard frequencies: 125, 250, 500, 1000, 2000,and 4000 Hz. Absorption occurs as the result of incident sound penetrating andbecoming entrapped in the absorbing material, thereby losing its vibrational energy