Face it. Our Onan three propane air cooled generator is unacceptably noisy.
And, the worst part? The fan that forces air over the engine fins is what makes the most noise.
And don't say to replace the generator.
1. We don't use it all that much.
2. It doesn't have a whole lot of hours on it.
3. I did replace all the sound insulation.
4. I did check everything. It IS the fan making the noise!! On the intake, thru the louvered door.
I just would like it quieter when we do have to use it in a CG or RV park.
I installed a baffle box to cut down on the discharge noise from the fan.
I added a down turned elbow extension to the muffler exhaust.
I have even contemplated making a sound enclosure that I would attach to the louvered door to attenuate sound or direct /block straight line travel of the sound.
Our 10K water cooled is also way too loud and I hear your complaint on the air cooled as they are even louder. Think blocking the direct path may work a bit. How about down also? Possible electric fan?
Going all LED with an extra 8D and inverter could be a plan.
That's the biggest reason we went solar. I can't stand the generator noise.
Pierce
Amazon.com: DEI 050220 Boom Mat Spray-on Sound Deadening to Reduce Unwanted... (https://www.amazon.com/050220-Spray-Deadening-Unwanted-Vibration/dp/B001URKV0G)
Have used this on the inside of louvered panels on generator door, helped a little bit.
Stationary air cooled engines have the fan as part of the flywheel and I see no way to reduce that noise at the source. Containing the noise in the compartment should be possible. I am not sure why your fan noise is the highest decibel problem. I have the same engine on my Miller generator/welder on the crane and the exhaust is the biggest offender. I added a second muffler which you probably don't have the room for to quiet mine.
Simply leaning a piece of plywood against the door lowers the outside sound quite a bit. Adding a sheet of 1/2 in foam board to it and maybe some folding sides should reduce the noise escaping. I see this at race tracks and arts events quite often .
As far as internal noise, it will require some more layers above the unit .
Adding an old wool blanket and a sheet of foam under the couch, In my case , directly above the gen may help. Make sure that your exhaust pipe is tight , has a good muffler and is not rigidly attached to the coach.
I've had three Onans, the first two were terrible noisy. This one, a propane "Marquis" is whisper quiet, outside and inside. The compartment is insulated, but I think, mostly, it's the Marquis.
Inside the coach are all LED lighting and LED TVs.
I fabricated a baffle box that I attached to the underside of the compartment. It is about 1/8" steel, has two baffles so the fan discharge direction is changed three times. Theoretically sound reduction of 50% each change in direction.
My muffler isn't the loudest sound. I put an elbow on it to direct the sound downward.
The exhaust should be directed away from the coach as carbon monoxide may be able to get into the coach, especially up at altitude where the generator runs richer. CO is not a factor with diesels.
Piece
whatever you do, pay close attention to where the CO goes and how much more heat is retained - the CO will kill you, the heat will kill the Onan
Tim Fiedler
Sure Start Soft Start (http://www.gen-pro.biz)
TCER Direct (http://www.tcerdirect.com) generator-gas-prod (http://www.generatorgasproducts.com) 630 240-9139
Gen-Pro
Generator noise,in the late 1980's I was assigned to escort 2 contract sound engineers for a day.I drove one of every model over the same route, They recorded noise levels from as many places in coach. Last recording, checking the two gen sets from around 20ft outside, no noticeable difference.
With aircooled there is very little you can do. You already nailed down the primary culprit: that fan. Honda addressed that with the eu3000is by using a large, slow squirrel cage blower with an electric motor.
Your best bet is to construct a labrynth out of plywood with open cell foam that "catches" the noise by changing direction and absorbing the sound vs reflecting it. Not easy to travel with, but effective. I use fiberglass insulation around my honda eu2000i while camped in the "no generators" lot at music festivals and have never had anyone complain. You cannot hear it ten feet away.
These new harbor freight 2000w inverter generators are $399 and work amazingly well. You might consider carrying one of these, they will run everything in my rv, including one rooftop AC although its loud while running at full power.
there are 2 components to perceived fan noise, one is the sound at the discharge or inlet, and one is the sound radiated from the metal housing surrounding the fan which you might be able to blanket with some insulation. I will crawl under my coach tomorrow and take a closer look. I believe there is some oppertunity to attenuate the sound inside the fan housing or adding some external features to reduce the noise. 3-4 db may be easy to accomplish, anything more than that it gets really difficult. high frequencies are much easier to attenuate than low frequencies. I have not gotten out the specs for this generator but I will assume it runs at 3600 rpm and not 1800.
Phred is right about the metal housing, just like in a car with big speakers and heavy bass, the metal vibrates and creates noise. I have used this type of sound deadening on the outside of metal generator enclosures.
Auto Sound Deadening Materials | Dynamat Alternative | FatMat (https://www.fatmat.com/)
I am quite familiar with the effects of thin sheet metal when it comes to noise.
I used to specify thicker sheet metal for machine guarding to aid in noise reduction, when I was designing machines. When I worked at Mercury Marine I was charged with noise attenuation for our entire plant.
My generator noise is totally fan related, unfortunately.
Unfortunately, our coach would look a bit strange with anything permanently fastened on the outside of the louvered generator compartment door.
Nitehawks I think we can add features to fan housing itself and/or inside of the generator compartment. Hmm we got a truckload of leftover dense/flexible rubber matting about 1/2 thick that was made for horse stable floors rotting in the warehouse yard.
yep the matting has not been thrown away yet
Long ago we were in Phoenix in dec 23 as they were closing for Christmas Eve with a blown armature in our propane Onan in a 1988 ORED.
The manager gave us a tour and mentioned how they sound insulated their installed gen's.
They used a rubberized cork panel to mount their engines on. Cummins/onan 17th and McDowell.
As a CC dealer later we bought the paneling from the or their source and built wooden boxes around our early power tech 8k diesel gens. Hinged door for access.
Personally I would scrounge a marquis gen somewhere