Peter’s Comments:
Stand-by electrical power generators have become almost commonplace in many retail commercial and residential properties. Along with this proliferation have come complaints of noise by adjacent property owners. Many municipalities have been unprepared to deal with this new type of noise complaint. Existing noise ordinances are frequently inadequate in their requirements for decibel levels lower than are achievable with this type of power equipment.
Generally the complaints centered not on generator use during emergency situations, but during non-emergency periods when generators are “exercised” which is usually on a weekly basis. These exercise periods may last up to several hours.
The purpose of this study was to consolidate all of the available information from the leading manufacturers of generators most commonly installed in the Town of Jupiter Fl and provide a cost benefit analysis regarding the additional cost incurred to provide quieter equipment.
NOISE LEVEL DATA FOR
STAND-BY ELECTRICAL POWER GENERATORS
400 Kw thru 1000 Kw
Prepared by:
Peter M Spirito
Town of Jupiter Building Department
Field Inspection Services
Wednesday October 3, 2007
Page1) Generator Noise Level at Full Load: Provides the maximum and average sound levels of various generator sizes
Page 2) Cummins Value Comparison: Provides a cost/value analysis of the added cost required to receive a reduction in noise level. The selected manufacturer, Cummins, represents approximately 50% of all generators in this size range installed in the town of Jupiter.
Page 3) Source Data: the original data as extracted from the manufacturers web sites.
Page 4) Understanding Decibels and Distance
Generator Noise Level at Full Load
|
Kw Size |
Cummins |
Koehler |
Caterpillar |
Max db(A) |
Average db(A) |
|
|
Weather Encl |
Weather Encl |
WP Enclosure |
|
Std Enclosure |
|
400 |
89.0 |
93.0 |
89.2 |
93.0 |
90.4 |
|
800 |
90.0 |
95.0 |
not available |
95.0 |
92.5 |
|
1000 |
90.0 |
98.0 |
not available |
98.0 |
94.0 |
|
|
|
|
|
|
|
|
Kw Size |
Cummins |
Koehler |
Caterpillar |
Max db(A) |
Average db(A) |
|
|
QuietSite-2 |
Level-2 Encl |
Critical Silencer |
|
Level-2 Enclosure |
|
400 |
73.0 |
68.0 |
86.3 |
86.3 |
75.8 |
|
800 |
76.0 |
70.0 |
not available |
76.0 |
73.0 |
|
1000 |
76.0 |
73.0 |
not available |
76.0 |
74.5 |
Caterpillar sound levels were not available on their web site and calls to Caterpillar distributors were not returned.
Cummins Value Comparison
|
|
Standard |
Quiet Site Level 2 |
Cost Increase From |
Percent of Increase
From |
|
|
Weatherproof |
Sound Attenuated |
Weatherproof to Level-2 |
Weatherproof to Level-2 |
|
1 |
2 |
3 |
4 |
5 |
|
400 Kw |
$112,884.00 |
$138,710.40 |
$25,826.40 |
22.88% |
|
800 Kw |
$261,484.80 |
$291,126.00 |
$29,641.20 |
11.34% |
|
1000 Kw |
$345,396.00 |
$372,734.40 |
$27,338.40 |
7.92% |
|
|
|
|
|
|
|
|
6 |
7 |
8 |
9 |
|
|
db(A) |
db(A) |
% of db(A) Decrease |
db(A) Reduction |
|
400 Kw |
89 |
73 |
-17.98% |
16 |
|
800 Kw |
90 |
76 |
-15.56% |
14 |
|
1000 Kw |
90 |
76 |
-15.56% |
14 |
|
|
Generator |
Standard |
Level 2 Sound |
|
|
Components |
Enclosure |
Enclosure |
|
|
400 Kw genset |
$73,056.00 |
$73,056.00 |
|
|
Weatherproof
Enclosure |
$8,500.00 |
|
|
|
Sound Enclosure
Level-1 |
|
|
|
|
Sound Enclosure
Level-2 |
|
$29,171.00 |
|
|
400 gallon fuel tank |
$7,428.00 |
$7,428.00 |
|
|
400 amp circuit
breaker |
$1,315.00 |
$1,315.00 |
|
|
|
$1,347.00 |
$1,347.00 |
|
|
|
$1,055.00 |
$1,055.00 |
|
|
150 |
$268.00 |
$268.00 |
|
|
Rain Hood Cooling
Air Inlet |
$530.00 |
$815.00 |
|
|
Industrial Muffler |
$571.00 |
|
|
|
Critical Muffler |
|
$1,137.00 |
|
|
|
|
|
|
|
total |
$94,070.00 |
$115,592.00 |
|
|
|
|
|
|
400 Kw |
Sell price with mark
up 20% |
$112,884.00 |
$138,710.40 |
|
|
|
|
|
|
|
800 Kw genset |
$157,190.00 |
$157,190.00 |
|
|
Weatherproof
Enclosure |
$41,100.00 |
|
|
|
Sound Enclosure
Level-1 |
|
|
|
|
Sound Enclosure
Level-2 |
|
$62,900.00 |
|
|
1000 Gallon Fuel
Tank |
$13,050.00 |
$13,050.00 |
|
|
800 Amp Circuit
Breaker |
$3,600.00 |
$3,600.00 |
|
|
|
$985.00 |
$985.00 |
|
|
|
$1,055.00 |
$1,055.00 |
|
|
Industrial Muffler |
$924.00 |
|
|
|
Critical Muffler |
|
|
|
|
Super Critical
Muffler |
|
$3,825.00 |
|
|
|
|
|
|
|
total |
$217,904.00 |
$242,605.00 |
|
|
|
|
|
|
800 Kw |
Sell price with mark
up 20% |
$261,484.80 |
$291,126.00 |
|
|
1000 Kw Genset |
$219,169.00 |
$219,969.00 |
|
|
Weatherproof
Enclosure |
$41,100.00 |
|
|
|
Sound Enclosure
Level-1 |
|
|
|
|
Sound Enclosure
Level-2 |
|
$62,900.00 |
|
|
2400 Gallon Fuel
Tank |
$20,700.00 |
$20,700.00 |
|
|
1000 Amp Circuit
Breaker |
$4,250.00 |
$4,250.00 |
|
|
|
$985.00 |
$985.00 |
|
|
|
$1,055.00 |
$1,055.00 |
|
|
Industrial Muffler |
$571.00 |
|
|
|
Critical Muffler |
|
$753.00 |
|
|
|
|
|
|
|
total |
$287,830.00 |
$310,612.00 |
|
|
|
|
|
|
1000 Kw |
Sell price with mark
up 20% |
$345,396.00 |
$372,734.40 |
http://www.cumminspower.com/na/technical/documents
Understanding decibels and distance
The intensity of a sound wave decreases with the increasing distance from the source. The farther away you are from the noise source the quieter it sounds.
The mathematical relationship between the sound intensity and the distance from the source is referred to as an inverse square relationship.
In essence when the distance from the source is doubled, (increased by a factor of 2), then the intensity will be quartered (decreased by a factor of 4). Similarly, if the distance from the source is quadrupled, then the intensity is decreased by a factor of 16.
The db(A) sound values used in the report were taken at 23 feet (7 meters) and that is the standard distance from the source used in all db(A) testing for all of the generator that were researched.
Having an understanding of the sound to distance relationship we are able to develop the following chart.
| Distance from source (feet) | Sound intensity in db (A) |
| 23 | 99.0 |
| 46 | 22.0 |
| 92 | 5.63 |
For more information on this subject refer to:
The Physics Classroom Tutorial, Lesson 2:
Sound Properties and Their Perception
http://www.glenbrook.k12.il.us/gbssci/Phys/Class/sound/u11l2b.html
If you have any questions please contact Peter Spirito at 561-718-7537