Air_US_rev_111.qxd
ACOUSTICS - BACKGROUND INFO
The standing waves are characterized by having a maximum sound pressure at the boundaries of the room. Depending on the frequency there are one or more dips across the room.
In a box shaped room the frequencies can be calculated as follows:
| f = c | ( nl | ) + ( nb | ) + ( nh | ) |
| 2 | l | w | h |
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where |
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f = | frequency in Hz |
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c = | speed of sound (approx. 340 m/s or 1130 ft/s) | ||||
l = | length of the room |
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w = | width of the room |
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h = | height of the room |
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n = | integer from 0 and up |
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How does the standing waves influence the sound field?
The maxima of the standing waves are shown in the figure. The curve expresses the area of the room where the actual frequency is audible. At the minima the frequency is represented at a much lower level (sometimes
If the room has the same dimensions as length, width, and even height it is very problematic to obtain an even sound distribution.
How to prohibit standing waves
Parallel walls in the room should be prevented. Then the strongest modes are suppressed.
When placing the monitors it is important that as few modes as possible are excited. This is why the monitors should not be placed in a maximum of a standing wave.
When monitors are built into walls you should therefore be concerned that the opposite wall is not parallel to the monitor wall.
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