Question

The volume of a room is 600 m³. The wall area of the room is 220 m², the floor area is 120 m² and ceiling area is 120 m². The average sound absorption coefficient for the wall is 0.03, for the ceiling is 0.8 and for the floor it is 0.06. Calculate reverberation time.
1. 1 s
2. 2 s
3. 3 s
4. 3.4 s

Answer 1

Correct Answer - Option 1 : 1 s

\(R{T_{60}}\; = \;\frac{{0.167V}}{{Sa}}\)

Where RT₆₀ is the reverberation time (to drop 60 dB), V is the volume of the room (m³), S is the total surface area of the room (m²), a is the average absorption coefficient of room surface (Sabine/m²) and Sa is the total absorption in sabines.

Given

V = 600 m³

Area of the room S₁ = 220 m², a₁ = 0.03 ⇒ S₁ a₁ = 6.6

Area of the floor S₂ = 120 m², a₂ = 0.06 ⇒ S₂ a₂ = 7.2

Area of ceiling S₃ = 120 m², a₃ = 0.8 ⇒ S₃ a₃ = 96

Total absorption, Sa = a₁S₁ + a₂S₂ + a₃S₃ = 109.8 sabines

\(T\; = \;\frac{{0.167V}}{{Sa}}\; = \;\frac{{0.167 \times 660}}{{109.8}} \approx 0.167 \times 6 \approx 1\;sec\)