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For a room wit h dimensions 4m × 3m × 3m (L × B × H), the details of i ndoor acoustical treatment are as follows.
The reverberation time in seconds at 1000 Hz is _______
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- 0.4 : 0.5
- 1.5 : 6.3
- 7.8 : 8.9
- 10 : 11.15
Correct Option: A
0.4 to 0.5
| t = 0.16 × |  |  | = 0.16 | | | = 0.37 Sec | ||
| A | 15.44 |
Calculation of ‘A' Wall area = perimeter of wall × height = [2(4 + 3)] × [4] = 56 m² = P
Ceiling area = 4 × 3 = 12 m² = Q
Floor area = 4 × 3 = 12 m² = R
So, A = P[(0.4 × 30%) + (0.1 × 70%)] + Q[(0.6 × 40%) + (0.1 × 60%)] + R (0.1 × 100%)
= P[(0.4 × 0.3) + (0.1 × 0.7)] + Q[(0.6 × 0.4) + (0.1 × 0.6)] + R[ (0.1 × 1)]
= 56[(0.4 × 0.3) + (0.1 × 0.7)] + 12[(0.6 × 0.4) + (0.1 × 0.6)] + 12 (0.1 × 1)
= 56(0.12 + 0.07) + 12(0.24 + 0.06) + 12 × 0.1
= 56 × 0.19 + 12 × 0.3 + 1.2
= 10.64 + 3.6 + 1.2
= 15.44 seconds
