Comparing Generator Set Noise Levels

by Visitor rosbor on ‎12-18-2014 04:56 AM - last edited on ‎03-10-2015 03:52 PM by Visitor Deb_EP

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Generator set sound levels vary greatly across the world because of different regulations regarding maximum noise levels. They can differ even further depending on other factors including the technology used by the generator set manufacturer, the measuring techniques and how the data is reported. This makes comparing noise levels from similar-sized generator sets confusing and in a lot of cases, imbalanced.


We’ve identified two major areas that make sound level comparisons easier. First, knowing where the generator set was tested is important because some countries require strict reporting standards while others do not. Secondly, testing techniques play a critical role in measuring sound accurately as the recording setup, equipment used and the amount of load applied to the generator set all impact the results.


Sound Levels by Location

In Europe, the Directive 2000/14/EC on noise must be implemented to provide an accurate sound power level (SWL or LWA) at a specified percentage of maximum load. Therefore, comparing generator set SWLs in Europe is fair because the measurements are taken from a standard production sample, and the measurement details are provided automatically. Additionally, the European directive requires three production units for certification, and periodic re-certification is required, which guarantees precise and up-to-date SWLs.

Non-European generator set manufacturers can also report SWLs, but they aren’t necessarily comparable because not all manufacturers are required to test generator sets with a standard production sample. Instead, the generator set manufacturer could report average noise levels that may not capture noise levels above the generator set where the exhaust effects can be significant. Additionally, manufacturers may report the noise levels at differing loads making comparisons between brands difficult.


Sound Power vs. Sound Pressure

Sound power is a measure of the energy that’s transferred constantly per second from the sound source in all directions and is independent of any external influences. Sound pressure is measured from a point near the sound source and varies by distance and is affected by external influences such as sound waves reflecting off walls.

An electric heater is a useful analogy for explaining sound power and sound pressure levels. The heater’s power is constant and just like sound power, the room conditions don’t matter. This means the heater will emit the same amount of power if the room is hot, windy, cold or damp. On the other hand, temperature will vary in the room and will generally increase as a thermometer is moved closer to the heater. Similarly, sound pressure will vary and increases as the recording equipment is moved closer to the generator set. This becomes especially significant when determining the optimum location for the generator set at a specific site.


Sound Testing Techniques

Noise levels are typically measured worldwide at 1m and 7m from the sound source. Noise should be measured using a sound level meter and an octave band filter set for a detailed analysis, but these tools are not always used. Advanced technologies including specially designed hemi-anechoic chambers for testing can increase accuracy, improve data analysis and provide clearer measurements, but not all generator set manufacturers have this luxury. The spectrum of recording equipment and test facilities is vast; therefore not all sound pressure levels are comparable.


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 Figure 1: Sound pressure tested at 1m.


Additionally, equipment configuration can have a large impact on noise testing. The number of microphones, the height from ground level and the load application all directly impact the results. For example, Figure 1 shows 11 microphones in various positions at 1m away from the generator set. Three overhead microphones are used to capture the noise from the roof/exhaust discharge, which may be significant, but some manufacturers may not measure there.


Caterpillar utilizes one of Europe’s largest anechoic chambers (Figure 2) located in the Larne Engineering Centre of Excellence in Northern Ireland. The chamber permits detailed analysis of generator set noise under free field conditions meaning there are no reflective surfaces above ground level to obscure measurements. The results are used to maximize product performance and reliability.


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 Figure 2: Hemi Anechoic Chamber, Caterpillar, Northern Ireland, UK.


All in all, sound level comparisons can be overwhelming for those trying to choose between different manufacturers. However, fair assessments can be made if the correct information is provided. It is important to ask where noise testing took place, which techniques were used to measure the sound and what equipment was used for recording. These three areas will help clarify what the noise levels really mean and how they can be applied to individual electric power system needs.


For more information, visit or contact your local Cat dealer.

  • When purchasing a generator set, what is the most important factor regarding noise levels for your operation?
  • How have noise testing techniques affected your generator set choices?

by Regular Contributor
on ‎01-30-2015 12:46 AM

I do not understand, there are small manufacturers grupppi who do not spend your money,, and unlike many super builders, have sold thousands of pieces, and are also within the EC Directive,

the noise is not an exact science, I saw so many facilities that according to the area, all in good standing near the car, but in kilometers had the noise of the exhaust in the house, or the cooling fan,

Now in reality ITALIAN, as when we have to carry out the tests sound with the appropriate bodies, usually use sound level meters on trestles as points in your numbers: 2,3,4,6,7,8, at a distance of one meter, then after the distance of 7 meters if you are outside, while for the machines but cofanate Installed above the roofs of makes only 7 meters away, cofanate machines in the basement, the same procedure of the exterior,
naturally peina power genratore I to use, being for the greater machines emergienza I small periods,

the permanent stations for the production (CHP) have diesel standards to the maximum of the restrictions, I personally have cases of noise level no more than you have 45 (40 + 5) decibels, and the request is normally not to exceed the background noise, which are three withdrawals nightlife of the area, the average over 5 decibels, (example 50 1 night, 2 night 56, 53 third night, the average reference diventoa the lesser of the three or 50 + 5)

Continuous has not exactly understand what your concern I fear for the control of noise from your products,
personalmento I've used several times the GC Series 800 and 900 both outside and inside of the place but shielded ultra protected area (hospice and senior center), replacing the previous installed inside iso containers super silenced, the best results we have had with the product cat almost standar, adding curved exhaust air fan motor bass muffler null having also added filters, and use in conditions CHP exchanger with vertical flue gas recovery,

have proved better than expected,

it is also true that many surely installer does not work with consciousness but is another issue, and not even make the site inspection of installation, just sell,

European directive least in all cases that I know and still follow at least 10 megs of diesel to vegetable oil that work continuously and trim CHP, with caterpillar included, and no, we are still in the rules, remember that the findings sound every two years we must give the ratio of the test to 'competent authority, and some areas every year,

greetings gordini


by Visitor rosbor
on ‎02-16-2015 05:22 AM

Thanks for your comments Gordini


At Caterpillar we are privileged to have the hemi anechoic chamber test facility. It means that we can test our products with confidence and can retest later and get the same results.  If we a test a upgraded version of the same product we can be confident in measuring the noise improvements accurately.

We have no concerns with additional noise sources which could be the case with testing outside or testing inside a test cell where reflective surfaces could obscure the measurements.

by Nicolette von Reiche
on ‎03-24-2016 07:51 AM

Hi Roger


Does caterpillar have a database of sound power or sound pressure levels for their diesel generator sets, with and without controls such as enclosures/exhaust mufflers etc. 

by New member Ciberopolis
on ‎04-21-2016 07:35 PM - last edited on ‎09-21-2017 12:47 PM by Administrator

I have no doubt thar CAT do their best job for creating the best enviroment for the employees in terms of noise levels...


by Aer Lingus
on ‎04-23-2016 02:35 AM

The absolute way to tell which is the quietest is to make all other factors equal.  That is, put them side by side and start them up one at a time.  By equal factors, I mean same surroundings, same thing plugged in (or nothing plugged in), standing the same distance away, EVERYTHING.  You can use a decibel (dB) meter if you need an actual measurement.


Chances are, the dB reading will differ from the one reported by the manufacturer.  Because conditions MATTER.

by Regular Contributor
on ‎04-24-2016 10:22 AM

the noise is not an exact science, the measurement can be considered an exact science, then the noise in the reality will always be different from the anechoic chamber, because it does not reflect the famous background noise that contrata with the sound level, and in certain areas the sound you perceive it to KM, while close to nothing, and I have thousands of similar cases, mountain valleys, enclosed places of ancient buildings,

but the quality of the materials the many cases makes the real difference does not count the sometimes thick, but the quality of the sound absorbing material is a good 60% of solve problem

Gordini greetings

by Regular Contributor
on ‎01-25-2017 12:59 AM

in India, I do not know, but around the world can not make a noise, but it is regulated by the authorities, according to zones, then it is also true the big cities suffer from noise, however, the installation of a generator can not It is carried out without taking account of the maximum allowed level of acoustic pressure, according to the minimum of perceived background noise,


Regards Gordini

by Alaa hussien
on ‎04-13-2017 03:00 PM
Please if I have a generator and I want to measure it's noise level, the generator now in villa basement and it's exhaust pipe is extended to the roof, this villa is 2 floors, roof and basement.
Now can I measure the noise level in basement with a 3 meters distance from the generator and how can I take my consideration the reflection in my measurements.


Best regards,

by Regular Contributor
on ‎04-14-2017 12:54 AM

then, enclosed spaces and installations between the houses, much is the wind or air currents, because carrying the sound, so you measure the noise level, but Misurale where it is believed to perceive more, the source often does not solve the problem, try to understand this, the engine exhaust shall be taller than the roofs of the houses if possible, the bass is the worst source, to eradicate


regards Gordini

by Karan m s
on ‎04-22-2017 12:28 PM

I need the decibels level for CAT generators  the rp3600 potable???


by New member amadorsurvey
on ‎04-22-2017 10:38 PM

I recently bought a 19 kw cat diesel generatorwith enclosure. I would like to be able to obtain information on buying the foam insulation used to further insulate the roof and side of the interior. Apparently it uses 2 types 1  has a protective coating for heat and the other does not. Does anyone know the MFG company that carries this material?

by New member OutlookGM
on ‎10-04-2018 06:51 AM

We are developing technology to reduce rpm on Diesel Gensets. Can you please provide noise level in dB for a 500kw genset running at 1500 rpm vs 1800 rpm, same load? If you have other info for larger gensets that would also be appreciated.

Kind regards,


by Regular Contributor
on ‎10-04-2018 08:43 AM

I do not understand the question, then ask you can answer is courtesy, however, ask qiu data that are on the web, without problems is a little strange,

however, the sound pressure of a machine in full power but with engine rpm difference, can not be the same

greetings gordini

by New member OutlookGM
on ‎10-04-2018 09:11 AM
Hello Giordini
I did not say it should be the same. Take a 500 kw genset. What is the db reading at 1500 rpm and what is the db reading at 1800 rpm. Thanks very much.
by Visitor Noman_akhtar
on ‎10-20-2018 04:44 AM


Good day


i want to ask you about caterpillar CSZ 1005 Kw gas engine its not taking load above 400 kw i have already checked compession, exhaust leakages, throttle position and feed back it is working properly but still i have accuring problem of underload 

please give me advice to fix the issue ASAP


Noman Akhtar

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