How can I make my generator less noisy : LUSENET : TimeBomb 2000 (Y2000) : One Thread

Had to use our new generator for the first time because of Floyd. Saved hundreds of dollars in food but was extremely noisy. I believe I saw an earlier post on how to baffle the noise of generators...can't find it now. Could someone please help.

-- (, September 20, 1999


Basically, you want to insulate the contact with the floor and to build a "dog house" with sound-deadening insulation inside. You do need to ensure that there is sufficient air circulation for cooling and "engine intake". You might also look at a better muffler.

-- Mad Monk (, September 20, 1999.

for some reason,-----and I don't know why!


-- David Butts (, September 20, 1999.

My husband put cement board on the walls, with the canned insulation in all the cracks of the room we built for the generator. Then he piped the exhust outside and he bought a 15 dollar car muffler that fit the pipes. We now hear the noise from the motor but not the exhust. We have a 1000 gal LP tank hooked up for it along with out other 1000 gal tank full. hope that helps. Jo

-- JO (TJ4261@GENESEO.NET), September 20, 1999.

here's a link:

Buffalo Bob's Silencer

-- BB (, September 20, 1999.

Fooled you didn't I? Try this:

Poor Man's Generator Noise Reduction

We all want a quiet genset, right? Here are the details of what I did to quiet down my small genset.

A small gas engine makes a lot of noise. I have read that the better engines such as Honda are inherently more quiet than cheaper ones. My engine is a cheap one and therefore the results are more significant. I have a 1000 watt generator powered by a used 3 1/2 HP Briggs & Stratton engine which just screams at full load.

First of all there are two distinct noises that an engine produces; exhaust noise and engine mechanical noise. Before I began this project, I thought that exhaust noise would be the greater of the two, now I am not so sure.

To reduce the exhaust noise I went to my local lawnmower repair facility. I highly recommend finding the one in your area and spending a little time getting to know the folks there. They are very helpful and there are always "jewels" to find out there in their graveyard. I talked to them about muffler options and quickly found that there are no "general" stock items for such an application. I did use the yellow pages and called a few generator places, including Honda, and found there are some new spark arrester mufflers, like the type used on Generac 4000 and 5500 XL's. These mufflers "promise" to be quiet but at a hefty price $85 plus. I have not heard anything operating with these type of mufflers, so I don't know how effective they are at noise reduction. If any of you have a genset with one of these then please share your experience.

Out in the lawnmower junkyard, I got a 100 cc moped muffler and mounting bracket for $6. A quick trip to Home Depot, some 1/2 inch galvanized pipe and fittings and, presto - a great super-low tone muffler.

Now that I got the exhaust noise greatly reduced, it was time to deal with the engine's mechanical noise. I got some free scrap 3/8" plywood from a construction site (amasing what they will let you have for free if you just ask). I built a 5 sided box shroud, 4 sides and a top, and lined the inside with fiberglass (also free from scrap).

I know what some of you are thinking, what about ventilation for the heat? This shroud sits over the engine portion of my verticle shaft genset, in such a way that allows plenty of room for the engine's forced air paths to exit. Most of the forced air is directed at the exhaust port and cylinder head. The top of the shroud has a 6" circular opening to draw cool air right into the engine's cooling fan.

I ran my genset for 5 hours under load and noticed it seemed to be no hotter than without the shroud. I am not saying it was not ANY hotter, just that I could tell no difference. The noise reduction, however is terrific! Before making the wooden shroud, I used a large cardboard box as a prototype. The wooden box was amasingly better, due to the fiberglass insulation no doubt.

With the engine's mechanical noise dramatically reduced, I found that the moped muffler I used was emitting more noise that I wanted. You know how a project can get once you get really into it. I went to my local auto parts store and bought the cheapest car muffler they had for $25. I installed the car muffler and WOW, one quiet genset! If there is ANY exhaust noise, I would need NASA scientists to come by with sensing equipment to show me, my ears hear none at all.

For comparative purposes; The Generac 4000XL's noise specs are 86 dB at 3 1/2 ft 73 dB at 23 1/2 ft

My Generator's noise specs are 88 dB at 3 1/2 ft 75 dB at 23 1/2 ft 70 dB at 33 ft

I was pleased to get such close sound specs to a new Generac. I think that if I started with a new engine the specs would be a little better. This engine burns 1/2 quart per 15 hours of use, so obviously there is some serious wear that's already taken place during its life.

The end result is for a $ 35-40 investment, both mufflers (who knew) the galvanized fittings and all, and a few hours of labor I ended up with an very quiet genset. I wish now that I had also taken dB readings before starting this project. I can tell you, it was a LOT louder. I think I'll bring it all down and show the guys at the lawnmower repair shop, they'll get a kick out of it.

If anyone has any suggestions or comments I would appreciate them. We're all here to learn from each other and to share what we find. I hope the information I have presented here helps another Y2K'r out.

-- Buffalo Bob (, January 11, 1999

-- BB (, September 20, 1999.

Try this:

generator muffler

-- BB (, September 20, 1999.

Don't try that

-- BB (, September 20, 1999.

You could use this...

A 1' long, 3" dia, pipe nipple. Cap one end of the nipple with a 3"

galvanized threaded cap. Either cut slots, or drill holes into the

pipe nipple. Stuff the end of the nipple with steel wool, and next add

bb', don't worry I'm not headed THERE....LOL... next, stuff the

rest of the pipe nipple with chore boy(tm) dish scrubbing pads (metal

pot scrubbers), bell reducer to reduce to fit as described by BB, and voila.

The chore boy (tm) will muffle the initial blast from the exhaust, the bb's will disperse heat, and the steel wool will finish the job. It will reduce the noise to an acceptable level, but not with the efficiency of BBs' contraception. It will just cost a lot less for those that find pennies regaining popularity again.

Steel wool alone will burn up. In fact it is my favorite wet weather fire starting aid. Ergo, the bb's. They will insulate the steel wool from enough heat while letting the offending vibrations pass through to be muffled by the steel wool.

Total cost about six bucks. If I am close enough to ppl to be worried about more noise than this, the situation is realy bad, and I haven't bugged out far enough.

-- Michael (, September 21, 1999.


I believe the set-up you have described will increase the back-pressure on the engine to unsafe levels. The life of the engine will be dramatically reduced. Try something less restrictive.

-- Pinkrock (, September 21, 1999.

After adding a car muffler to my generator, I still found it a little too noisy, so I stacked some ordinary concrete blocks (at 45 degrees) a couple of feet in front to the muffler's exhaust pipe to deflect the noise away from the direction of the road and into the bush.

-- John (, September 21, 1999.

Three of us bought the same Winco Dyna 9000. We all are experimenting with mufflers. A welder friend of mine told me when you add to your stock pipe, you need to make sure it is lighter. If it is heavier, it will cause cracks from the vibrations.

What we are doing is soldering a piece of copper to the stock pipe, adding a flex pipe, so it will go with the vibes and then our muffler affixed to whatever you want. b

-- BB (, September 21, 1999.

If you are trying to muffle a generator, I think you are doomed before you start. First, no matter how well muffled, there will be some vibration, some noise, picked up by some person who has good hearing. Some can hear an idling boat from miles away, just depends on conditions.

And you are facing a situation where you cannot afford to have ANYONE hear you at all. That's what you're trying to do, right? But even after muffling it, you'll never know who heard or how close they're getting as they track down the noise. They're out there in the dark and you're not going to know where they are.

I suggest you either team up with enough people that you can share and protect your generator, or don't use one.

Think low tech, or avoid internal combustion. Use solar, use hand-crank. Don't freeze or cool food - eat what you cook. Preserve by drying. Cook on wood or charcoal. Do you really need that generator? We looked at our requirements, at the fuel problems, at our personal limitations, and decided to skip it. It might take a little adjustment, but maybe you could solve a lot of problems by not using one.

-- bw (home@puget.sound), September 21, 1999.

Or a high-tech solution: buy one of the new Honda ultra-quiet inverter/generators.

They have a built-in, clean-power, sine-wave inverter, and are hardly louder than normal conversation (although a different sound, of course). dBs are about 52-57...

I got one of the little EU1000i ones (~1000 watts) to recharge my battery bank and it's amazingly quiet. With it sitting in my garage, I can't hear it above ambient outdoors noise when I stand 50 feet away (my closest neighbors are 2-3 times that far away).

Oh, and they little one weighs only 26 pounds. Honest. You can pick it up with just 2 fingers.

And the cost is only ~$600-$700 (i.e., about 1.5 times what a cheapo Coleman, Wal-mart unit costs). The lifespan (dunno if it's total lifespan or mean-time-between-failures lifespan) is about 500 hours on a Briggs-Stratton or Tecumseh engine, but on a Honda it's about 10,000 hours (these figures are from memory - your mileage may vary).

The bigger model (I believe EU3000is) is more normal-sized/weighted, but is just as quiet. More expensive (~$1300) but is about 3K watts. Not huge output, granted, but it IS awfully stealthy...

I can't wait to cobble together a muffler/enclosure to see how quiet it can really be.

I got mine at Mayberry's, but I've also seen them in the usual catalogs (Northern, etc.).

Sorry for gushing, but I love this little thing - I've begun using it around my mini-farm instead of running long extension cords. If you don't already have a generator, get one during the lull in sales we're seeing now.

-- Hugh (, September 21, 1999.


You certainly have a right to your opinion, but the math doesn't support it. In fact, as an example, as kids we pumped 8 big bore pistons, at 12:1 compression, pushing 375 horsepower through a six inch muffler. True, it wasn't quiet, but back pressure wasn't a problem, unless of course some AH put a potato(e) in the end of the tail pipe.

Here, we're talking about a 196 cubic centimeter single lung (piston) engine, with a 85.5 mm exhaust port ( as measured with my vernier caliper) conducted to a tank ( 1' long x 3" dia) 84.7 cubic inches/(1.061 * 84.7 =89.86 cc) or approx. 45% of the displacement of the engine. To transpose these numbers to a dream machine of eons past, the muffler on my GTO would have to measure roughly the size of three Mack truck, full size, exhaust stacks ( chrome preferred ) to equal the example of a muffler I described above. Besides...

Pressure is a. not static, b. omnidirectional, c. easily relieved ( see; cut slots or drill holes in the pipe nipple (above) While sound/vibrations/waves/noise tend to be a. a static effect relating to a function, b. directional c. easily commandeered and absorbed (example; when building a sound proof room, simply stagger the wall studs between rooms with enough space between the wall surfaces to allow insulation to be woven in an out of the studs, creating a disruptive surface for the sound waves entering the wall and changing it's through path to the adjacent surface and beyond.) [See also egg cartons][g.]

So this cheapy muffler redirects/confuses/absorbs the waves/vibrations to quiet the scream of my Tecumseh, while disarming pressure and heat. I'll wait to unbox the Generac 5500XL until circumstances warrant, by which time I will be far less worried about prying ears.

Aside; Remember to store some various oils and lubricants for the long haul. Cheap insurance.

-- Michael (, September 22, 1999.

Saw a couple ideas on other boards that might help. I haven't tried them yet, but will soon. 1) muffle the exhaust, and vent it into water. Bubbles make less noise apparently. 2) use sount absorbent tiling on the inside of the plywood enclosure.

I've set up a solar system that should do the trick, and the generator is for natural disasters/long cloudy stretches.

-- Bill (, September 22, 1999.

Get two large 'jello' seats from the local bike shop, like the ones for indoor exercycles. Cut each in two with roughly the same square area. Get a pc of 3/4 plywood big enough to support the genset. Place the jello pads where the corners of the plywood will rest. Place the plywood on top and then the genset on top of that. You should be able to wiggle the genset an inch in any direction with your pinkie finger.

That should isolate the genset from a floor surface which might act like a 'loudspeaker'.

Also did the muffler thing and surround with fiberglass insulation at a safe distance. Now it sounds like a very small japanese car. Will tinker with this some more.

This on a 6.5 Kw diesel genset. Was very noisy before.

-- ..- (dit@dot.dash), September 22, 1999.

get 4 20' sticks of 2" diameter pipe, threaded each end, and 3 pipe couplings of the same diameter. Connect all the pipe together and bury it about 24" below grade, with an upright length at each end to allow you to connect to the exhaust port on one end, and to simply stick out of the ground a few inches (down the street-in your neighbor's yard.) The looters and vandals will terrorize yer neighbor, not you!!

-- Jay Urban (, September 22, 1999.

Hooray for Jay! LOL With all the "don't worry" to worry about today, I needed a good old fashion belly roller!

-- michael (, September 22, 1999.

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