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Lothlorian 12-19-2008 11:29 AM

Sound proofing my generator
I have a 3000 watt generator which is not as loud as most but not as quiet as the honda. I only use the generator when we go to our retirement property. I want to build a sound proof box or container to make it as quiet as possible when we are camping. I have it sitting in the grass when we camp. This box would stay at the property and will never leave. I want to make sure it will keep the generator quiet, cool and fire resistant. Does anybody have a good plan they have used to construct one, or a good picture


vinstream 12-19-2008 02:11 PM

Great question... You can build a box but two things to think about... The generator needs a good supply of cool freash air! And needs to also vent heat build up. The very best way to do this is to build a custom muffler that bolts onto the header. This custom muffler would do two things! Vent the heat out of what ever box you build and second (your main goal) reduce the noise as much as all of it if built correctly! So the box would mainly hide and protect the Generator. The best way to keep the box cool is to add an exhaust fan that sucks out the heat (not blow air it into the box)! The custom exhaust can run up to $100 and will reduce 80% the noise and the box will reduce the rest of the engines noise (keep in mind that these engines were never desinged to be quite!).... Vin

P.S. the best muffler for this that I have found is OEM motor cycle mufflers...

dbradhstream 12-19-2008 03:16 PM

There are some manufacturers you can find online that make boxes for generators that include an exhaust fan. I went the "homemade" route and built a plywood box with vent holes, etc. - even went to a muffler shop and had an exhaust extension custom made (cost about $50) to route the exhaust out of the box. I thought I had practically invented the wheel I was so proud of my box.

BUT, the generators (I have two Honda eu2000s) generated more heat than I thought, and it's blazing hot here (in Fla) in the summer, and I didn't install a fan, so my generators overheated and shut down repeatedly when I tried to use them in the box. I spent several hundred bucks on materials to build a beautiful, non-functional, generator box that now takes up a lot of room in our garage and that my wife and I just refer to as "The Box", as in, "when are you going to move The Box out of here?"

The Box would work if I bothered to put in a fan, but after all that I decided my Hondas were quiet enough without The Box so I don't even mess with it any more.

SO, lessons I learned: (1) Don't try to reinvent the wheel - there are already some really nice generator boxes on the market that won't cost you much more than you'll spend anyway on materials and time and effort and, oh yeah, they'll probably actually work, and (2) If you do build a box, put in more vents than you think you need and install a very good exhaust fan that will move a lot of air b/c that generator will get really hot, really fast, without it.

Wayne&Sam 12-19-2008 03:26 PM


Originally Posted by Lothlorian (Post 649171)
I only use the generator when we go to our retirement property.

If you are only trying to keep the noise away from you and you don't have neighbors, you only have to screen the sound from your side. You don't need a complete box, one or two sides could be open and you wouldn't have the heat problems.

dbradhstream 12-19-2008 03:31 PM

Now that is a pretty da#* smart observation - nice work W&S!

Fyrzowt 12-19-2008 03:31 PM

Some good points made, I have a couple of observations:

The box needs to be lined with an acoustic absorbing material.

The box needs venting for the Genny to get rid of heat. The fan idea is probably the way to go, this would reduce the amount of vent square inches needed. The more vents you have, the more sound is going to escape.

Direct the exhaust directly out of the box to reduce internal heat. This will require a modified muffler such as suggested above. Make sure that the muffler is fully supported by brackets - if you don't, the vibration will either break the muffler, or pull the mounting threads out of the engine head.

Let us know what you do and how effective it is.

Lothlorian 12-19-2008 06:57 PM

The screen sounds like the best way for me to go. I do not have neighbors. If I can just keep the sound away from the trailer then I am good.


Fyrzowt 12-19-2008 08:10 PM

In that case, I would shape it something like a baseball backstop to direct the sound away. And line the interior of the screen with acoustic panels.

Mikethefixit 12-19-2008 11:54 PM

I dont think U indicated what brand engine your geni has but there is a mfgr that makes a muffler for small engines CALLED a SUPER TRAP .I have heard it helps. I know I have a 3500 watt Briggs powered Geni and its loud.

imeynstein 12-20-2008 12:09 AM

I have another question!!! I am thinking of replacing my univolt--the hummer--with an intellivolt---for two reasons---My univolt is original to my 1974 AS sovereign and now my interior front and rear lights do not come on...If I replace my univolt with an intellivolt, will there still be that loud humm???? Also, I am hoping that by replacing my univolt that my lighting will return....Perhaps I am hoping for too much... BTW, I am trying to do everything myself as my husband is not helping me....He told me it was 'my project'...I am sure that when it is deer season, and once I get everything fixed, he will be more than happy to take my AS with us.....

Lothlorian 12-20-2008 04:17 AM

I used the fuse panel from my univolt and connected it to an intel. There is not any sound.


GStephens 12-20-2008 07:11 AM

The act of changing out the Univolt is not likely in and of itself to repair your lights. Check your 12 volt fuses.

jdalrymple 12-20-2008 07:57 AM

I made a screen from 1/4 plywood ripped via a table saw into 3 pieces 4 foot tall and 18" wide. I connected them along the edge with cheap hinges to create a japanese screen, so to speak. I then bonded, with construction glue, 1" of the pink foam board to the screen. It all folds flat, hauls easy, and works like a champ. It deflects the noise away from the trailer well. I do have a Honda invertor generator.

A muffler change on a standard altenator type gen set will make some difference, but most of the noise is due the fact the engine must run high rpms to make 60 hz 120/220 volt current. It is still going to sound like a lawn mower running.

Invertor type sets use electronics to adjust voltage and freqency, and operate a lower speeds.

Best Regards,

Wayne&Sam 12-20-2008 09:09 AM

That's the ticket, Jeff. For Lothlorian's application, it wouldn't have to be portable so I'd add a roof so the gen can be run in the rain without getting wet.

Lothlorian 12-21-2008 03:05 PM


Great idea! I think that is what I will do. I have left over pink board, hinges, and liquid nails.


ROBERT CROSS 01-06-2013 11:14 AM

We use a tent and a tree....out of sight out of min 'er....ear.;)


Inland RV Center, In 01-06-2013 11:46 AM

Loud noise from a generator, is cause by the heat expansion from the gas exhaust.

An easy fix, is to cool the exhaust before it hits the atmosphere.

Simply extending the exhaust pipe, makes a large reduction in the noise.

Try it with just a junk piece of pipe and you will quickly hear the different.

Once you do that, then you can design an exhaust pipe system that takes up a small space.

The cooler the exhaust, the less the noise.

In fact, on a larger generator, you will probably hear more noise from the working parts of the generator, than you would hear from the exhaust

Easy, cheap but effective fix.


Alphonse 01-15-2013 04:20 PM

Andy is correct about the heat and given enough volume and surface area for heat transfer that is a possible solution. I am reminded though of a school bus that I used to ride as a kid that had a 40 foot long exhaust pipe that sounded like a machine gun. It is the size of the pipe that matters isn’t it?

Seriously another big aspect of the noise for an IC engine is pulsing of the exhaust gas. It is this pulsing and the pressure waves that cause much of the racket that annoys the neighbors. This noise is generated by the exhaust valve opening and the corresponding pulsing of the exhaust gas expanding as part of the blow-down process. It is this pulsing that a good silencer (muffler) system dampens and thereby reduces noise. For example, the exhaust on a small Honda generator is not cooling the exhaust gas to any great extent simply because of space and layout constraints. They are cleverly removing the pulsing of the exhaust through an elaborate exhaust/silencing system. On a well-made system such as the Hondas and I assume the Yamahas, you will find they are able package a silencer in a very small space and therefore the cooling of the gas is likely quite marginal. But with their designs, they are able to dampen and smooth the pulses thereby reducing noise.

The trick used by Honda is to dampen this pulsing blow-down is through a very elaborate silencer. I once saw photos of an exhaust silencer from a Honda generator that had been purposely cut open for evaluation of its cross section and it was more elaborate than one might expect. They are obviously quite cleaver as to how and the extent they are able to dampen, isolate, and smooth the pulsing thereby eliminating noise. Again, no significant heat transfer but pulse dampening and smoothing. They are trying to achieve constant flow from the exhaust tip vs. something that pulses like a beloved Harley exhaust!

By the way, an even more efficient silencer is a turbo charger which reduces heat by creating work from the flow and smoothing the flow throw the vanes of the rotor. So another solution would be to turbocharge that Briggs to take some of the noise out.

These muffler/silencer designs, employed by Honda and others, drive the cost up. You gets what you pay for, sometimes!

mlts22 01-21-2013 09:33 PM

One thing I've heard about from people coming back from desert countries, is for dealing with a loud open-framed generator that usually sits in one location, is to use sandbags. You pile sandbags around the generator (giving proper air space) in a square "Q" shape. You pile them up about a foot or two higher than the generator. The tail of the "Q" is bent and where the exhaust goes. Because the noise then goes upwards, it should help immensely with quieting it. Digging and shoring up a hole also does similar, except one has to be careful about drainage.

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