| What is sound absorption coefficient? I is the intensity of sound incident on an object. i , Then the intensity of the reflected sound I rThen, it is given by the following equation. Sound absorption coefficient Ώa1- (Ir / Ii)B | ||||||||
| material | thickness t / mm |
specific gravity | Ώa | |||||
|---|---|---|---|---|---|---|---|---|
| frequency@@f / Hz | ||||||||
| 125 | 250 | 500 | 1000 | 2000 | 4000 | |||
| Glass wool board (Adhesion to rigid walls) |
25 | 0.016`0.024 | 0.08`0.16 | 0.22`0.34 | 0.54`0.71 | 0.71`0.88 | 0.69`0.88 | 0.77`0.94 |
| Glass wool board (Adhesion to rigid walls) |
50 | 0.016`0.024 | 0.13`0.27 | 0.55`0.75 | 0.87`0.98 | 0.78`0.93 | 0.69`0.86 | 0.73`0.98 |
| Glass wool board (Behind air layer 100mm) |
25 | 0.016`0.024 | 0.18`0.33 | 0.53`0.75 | 0.84`0.98 | 0.78`0.92 | 0.70`0.86 | 0.77`0.94 |
| Rock wool (Adhesion to rigid walls) |
25 | `0.12 | 0.04`0.09 | 0.23`0.34 | 0.58`0.80 | 0.78`0.91 | 0.75`0.84 | 0.75`0.90 |
| Rock wool (Adhesion to rigid walls) |
25 | 0.12` | 0.05`0.16 | 0.26`0.50 | 0.70`0.92 | 0.80`0.97 | 0.72`0.93 | 0.77`0.96 |
| Soft urethane foam (Adhesion to rigid walls) |
20 | 0.01`0.02 | 0.06`0.11 | 0.16`0.24 | 0.32`0.42 | 0.47`0.58 | 0.54`0.67 | 0.56`0.70 |
| Sprayed asbestos | 12 | 0.2`0.3 | 0.02`0.06 | 0.08`0.16 | 0.30`0.50 | 0.60`0.84 | 0.74`0.92 | 0.82`0.96 |
| Wood wool cement board (Thick wood wool) Soft fiber board for sound absorption@(Wooden baseABehind air layer 300mm) |
25 | 0.43 | 0.01 | 0.10 | 0.23 | 0.64 | 0.69 | 0.73 |
| A@(Hole diameter 5 mm Σ-pitch 12.7 mm) | 9 | | | 0.27`0.39 | 0.24`0.38 | 0.38`0.52 | 0.55`0.59 | 0.67`0.68 | 0.77`0.78 |
| A@(5Σ-12.7) | 12 | | | 0.35 | 0.28 | 0.45 | 0.64 | 0.75 | 0.83 |
| G@(Needle hole) | 9 | | | 0.33`0.40 | 0.30`0.33 | 0.38`0.41 | 0.30`0.48 | 0.27`0.47 | 0.30`0.47 |
| Rock wool ceiling sound absorbing board@(Steel base,Gypsum board underlay, back air layer 300 mm) | 12 | | | 0.28`0.32 | 0.22`0.32 | 0.42`0.48 | 0.52`0.74 | 0.64`0.79 | 0.67`0.87 |
| Perforated gypsum board(6Σ-22, base paper backing for boards,Behind air layer 300mm) | 7 | | | 0.63 | 0.51 | 0.29 | 0.21 | 0.25 | 0.31 |
| Perforated board (5Σ-15, glass wool board 25mm base,Behind air layer 150mm) | 4 | | | 0.25 | 0.74 | 0.86 | 0.46 | 0.45 | 0.28 |
| Perforated board (9Σ-15, glass wool board 25mm base,Behind air layer 500mm) | 5 | | | 0.83 | 0.72 | 0.80 | 0.90 | 0.87 | 0.70 |
| Citation: "Science Chronological Table" (National Astronomical Observatory of Japan, 2000 edition) Physics / Chemistry Sound 74 (498) Quoted from sound absorption coefficient. | ||||||||