Page 21 - Laqfoil Acoustic Catalog

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Note: These calculations are simplified and should be used as an example only:
Example of Acoustic Calculation for a Home Theatre Room
1. Calculate the optimal reverberation time:
First, decide what the main thing listened to in the room will be. In this example, the room will mainly be used for movies, and occasionally for music.
Reference Table: Sound Absorption Coefficients
Sound Absorbing Surface
Average Coefficient of Sound Absorption
Concrete Wall, Unpainted
0.02
Brick Wall, Unpainted
0.04
Gypsum Plaster
0.05
Gypsum Plaster
0.04
Wood Paneling
0.07
Wood Floor
0.04
Marble or Tile
0.01
Parquet
0.11
Linoleum over solid base
0.03
Glass
0.03
Curtains
0.18
Drapes
0.54
Carpet
0.36
Armchair
0.33
Pool Water
0.01
a. Calculate the volume of the room in cubic metres, by multiplying
length times width times height. The room is 6m x 4m, with a 3m high ceiling.
V = 6 x 4 x 3 = 72m3
b. Calculate the optimal reverberation time for the room.
For home theatre, the formula is:
Sound absorbent surface
Surface Area, m2
Average Coefficient of Sound Absorption, αω
Floor
24
0.11
Walls
60
0.05
Ceiling
24
αω ceiling (the rated value that we are interested in)
Sofa
3.5
0.33
Curtains
9
0.40
Carpet
5
0.36
Topt1 = =
=
0.4 lgV - 0.15 0.4lg 72 - 0.15 0.59 (±10%)
The optimal reverberation time for the two uses turns out to be quite close. For a combination of the two uses, we shall use a median optimal time for our room of Topt =0.61 for the rest of our calculations.
For listening to music, the formula is:
Topt2 = =
=
0.5 lgV - 0.3 0.5lg 72 - 0.3 0.63 (±10%)
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