- in Generator , Power Tools by David Miller
How To Quiet A Generator
If you want to know how to make your generator quieter then you need to know where the noise is coming from to begin with.
The source of the generator noise is the small internal combustion engine. Essentially what you are hearing is the small gas explosions happening in the cylinders as well as the sound of the rotating parts that make up the rest of the engine.
Most of this sound moves from the inside of the engine and out through the exhaust. If you haven't bought your generator yet then check out our portable generator buying guide. If you've already bought the quietest generator on the market and want to quiet it even more then try the following.
Add Muffler and Extend Exhaust
The quietest generators will have a muffler attached to the exhaust which performs the same function as the one on your car. It reduces the intensity of the generator noise coming out of the exhaust. These are great if you want your generator to be super quiet.
Some people have added extensions to the generator exhaust. The longer the exhaust, the quieter the generator.
Of course, there’s a practical limit to how long you can make the exhaust. You could eventually end up with a really quiet generator that is no longer portable.
Also, increasing the length of the exhaust increases the back pressure and will strain the engine of the generator.
You can also cover the generator with a portable generator cover. This will make the generator quieter but you need to ensure that the cover is well ventilated. You could even make your own generator cover.
Just remember that the generator will produce heat and also needs oxygen to keep the engine running so ventilation is important. Your generator is air cooled so free flowing air is a must.
Quiet Generator Box
Using a quiet generator box or angled panels to surround the generator will also reduce the noise. Even if you decide to leave the top off for ventilation you will still be making it quieter. The sound will be deflected upwards and less of it will reach your ears.
Put It Further Away
For every doubling of the distance between you and the generator the sound intensity will be four times lower.
So, an inverter generator that is 20 feet away from you will have a sound intensity four times lower than if you stand 40 feet away.
This is a similar point we make in our quietest dehumidifier post. If you reduce the sound intensity by ten times then it will sound half as loud to you.
So, by moving it just over four times the distance away it’ll sound half as noisy. If you’re camping then make sure that when moving the generator you don’t end up putting it closer to your neighbours. Even a super quiet generator can be annoying over time.
Use Dampening Materials
Manufacturers of the quietest generators will use noise absorbing glass wool inside a moulded casing to reduce the generator noise. If you’ve bought a cheaper generator that doesn’t have this material inside the casing you could try adding some.
The problem with using noise absorbing glass wool or foam is that these also act as insulators. They keep the noise in but also stop the heat from escaping or air from getting into the air intake.
Check that any added sound dampening material doesn't blocking heat or air passages.
Put It On A Soft Surface
A generator on concrete will always sound louder than if it’s on grass. If the surface has some give in it then it will help to dissipate the sound vibrations. It also helps to have decent rubber vibration isolation feet under the generator.
Switch It Off
It may sound obvious but the quietest generator is one that is switched off. When you do run your generator make sure that in addition to powering your equipment, it also charges deep cycle batteries.
When you want extra peace and quiet rather run your equipment directly from the batteries or via an inverter for AC equipment.
This is also a more efficient way of maximizing your generator output. No excess generated power is wasted because you're storing it in your batteries. Also, consider purchasing more battery powered goods instead of externally powered appliances.
Battery powered devices have come a long way and perform as well, if not better, than a lot of externally powered products.
Generator Noise Level Measurement
You’ve probably heard people use the word “decibel” when comparing sound measurements.
In simple terms it’s a unit of measurement for how loud a sound wave is. A sound measuring 0dB is the lowest sound a healthy human ear can detect.
Our ears are more sensitive to some frequencies than others so to correct for this the measurement used for the best sound level comparison is dBA. This scale adjusts for how our ears experience lower frequency sound waves like the ones that come from your generator.
You don’t need to understand all the science behind decibel levels and sound level measurements. The important thing to remember is that a lower dBA figure means a quieter generator.
Also, every increase of 10 dB means a doubling in how loud the generator sounds to us. eg. A super quiet generator with a 51 dBA noise output sounds half as loud as a generator that puts out a 61 dBA sound level.
Some of the best quiet inverter generator manufacturers will give a single figure for the sound output while others will quote a range of decibel levels.
If a quiet generator is rated at say 53dBA this is the noise level at 25% load. If it is quoted as 53dBA - 57dBA then these are the levels at 25% and 100% load.
A generator naturally gets quieter the further you get from it. The noise levels that are used to compare quiet generators are measured about 21 feet (US standard) or 23 feet (European standard) away. These are generally measured at 25% load.
You can expect that when manufacturers test their own products they’re going to fiddle with these measurements as much as possible to have their product end up being the quietest on the market.
So take these figures with a pinch of salt. All kinds of things like air pressure or density, humidity, what it’s standing on and other factors can affect the readings so use them as a guide rather than absolute figures.
Quiet portable generators will normally be rated at a noise level just above 50dBA. It’s difficult to imagine exactly how loud that is so here’s a good Noise Level Chart that will help you get and idea of what that sounds like.
Most city ordinances or Home Owner’s Associations will specify that you need to keep any noise you make below 75 decibels so if you are running any one of the quiet generators we’ve reviewed here then you’ll be way below that.
Generator Noise vs Power Output - The Tradeoff
If you get a generator with a 1000W output it’s understandable that it’s going to be quieter than a 3000W generator. More Watts means more noise.
If you’re looking for a quiet generator but want the best bang for your buck then you could look at the Watts per dBA figure.
If you take the power output of a generator and divide it by the quoted output noise level you get the Watts per dBA. Let’s say you’re trying to decide between a 1800W generator with a noise level of 53dBA and a 2200W one rated at 55dBA.
The first provides 34 Watts per dBA (1800/53) while the latter provides 40 Watts per dBA (2200/55).
That means that for every increase in Watt of output power the 2200W generator actually has a smaller increase in noise than the 1800W generator does. Remember, output noise levels of generators are measured at 25% of load.
For these two generators that would be at 450W and 550W respectively. You might even find that when you’re running both of these at around 1500W that the 2200W generator could be the quietest of the two. Even though it has the higher “quoted” noise level.
If you need more power but want to keep the noise to a minimum then it would be better to buy two smaller quiet generators rather than one big one.
The best portable generators will be parallel ready. This means that they have outlets that allow for two of the same generators to be connected in parallel by means of a cable kit.
Fortunately for our ears, sound isn’t additive but power is. This means that connecting two quiet generators in parallel will give us double the power but not double the noise.
There will be an increase in how loud the generators sound but it won’t be significant. Using two 2000W generators will be a lot quieter than a single 4000W generator.
Of course, while the sound doesn’t double the purchase cost will. It's worth buying two smaller camping generators if you don't want to disturb other campers.
Generator Engine Capacity
There is a direct correlation between the size of the engine and the amount of power (and noise) the generator can put out. More cc’s means more Watts.
Some of the quietest generators are more efficient than others which means that for the same engine capacity they can squeeze a few more Watts out. If you’re looking to buy a low noise unit then you definitely don’t want the one with the biggest engine.
No generator is ever going to be completely silent but if you use some of the strategies above then you'll definitely lower the noise output. The best way to quiet a generator is to use a combination of these approaches all at once.