With our increasing dependence on computer systems and the number of power outages experienced throughout the country, more and more companies are installing emergency or stand-by power generators. These generators can help to provide uninterrupted power for our technological needs. However, there is a concern:
Generators can be very loud!
Emergency generators can easily exceed 100 decibels. Generator noise is primarily comprised of two noise sources: engine noise and exhaust noise. NOTE: Often times, noise data provided by generator manufacturers will exclude the exhaust noise.
More than one generator
Obviously, the more generators in operation at one time, the louder the noise level. However, the noise level increase is not arithmetic and might not be as loud as you think. The following table demonstrates the noise level increase for multiple generators (assumes each generator is the same type and produces the same noise level):
|
Number of Generators
|
Noise Level Increase
|
Perception
|
|
1
|
-
|
-
|
|
2
|
+ 3 dB
|
"just perceptible"
|
|
4
|
+ 6 dB
|
"clearly noticeable"
|
|
10
|
+ 10 dB
|
"twice as
loud"
|
NOISE REDUCTION
The following noise reduction options are offered as simply tips, considerations and rules-of-thumb. We highly recommend you seek the advice from an acoustical professional to assess the particulars of your specific project. To find an acoustical consultant to help predict the generator noise impact, help determine compliance with the applicable noise codes, or to help control the noise impact, click here.Generator manufacturers and third-party vendors offer noise attenuation options for both the generator itself and the exhaust system, such as enclosures and critical grade silencers.
(Contact us for more information on these types of products.)
Distance
Every time the distance from the generator is doubled, the noise level is reduced by 6 dB. (A 6 decibel reduction is defined as "clearly noticeable".) Note: You must double the total distance, not the original distance, to achieve additional 6 dB reductions. For example:
|
Distance from Generator
|
Noise Level Reduction
|
|
20 feet
|
-
|
|
40 feet
|
- 6 dB
|
|
80 feet
|
- 12 dB
|
|
160 feet
|
- 18 dB
|
|
320 feet
|
- 24 dB
|
Barrier Walls
Barrier walls (of sufficient height & material) can substantially reduce the generator noise. To be effective, a barrier wall must at least block the line-of-sight from the source to the receiver. Note: The source height of the generator can be fairly high, particularly if it is installed on the tanks. Also consider the height of the receiver. Is the impacted site multi-floors?
The wall must also be of solid construction, such as concrete block. ("Solid construction" does not necessarily imply that the cells be solid grouted. It implies that the wall should not have openings or penetrations.)
Administrative Controls
Stand-by generators are typically tested for 1-4 hours 1-2 times per month. Although no one can predict when a power outage will occur, the testing can be scheduled during a non- (or less) sensitive time and day.
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Acoustics.com
