Help Needed to Reduce Installed Generator Noise

[rockerbox]

Has anyone figured out a way to reduce the vibration and noise from a factory installed generator in a Class C RV? The generator is below the sleeping area and under the floor of the rear bedroom, but leaves a lot to be desired when needed overnight.

If there have been successful mods to reduce the transmitted vibration and noise into the sleeping area, I sure could use the help.

Thanks in advance for any suggestions.

Bill

[rockerbox]

I think I'll first try to install a new floor on the storage compartment floor including absorbent material plus a layer of plywood, That will be the easiest to do. It should stiffen the layer just above the generator and should reduce some of the noise propagation from below. Since the generator is supported from this floor structure, I suspect most of the vibration noise is transmitted from that surface. Thanks to DrewE and all for the suggestions.

[DrewE]

"Thin" and "sound absorbing" don't go together very well. Adding structure to stiffen the panels so they can't vibrate as much could help. That is blocking transmission, tather than absorbing sound. A laminated structure of rigid foam sandwiched between two sheets of plywood or similar sheet goods is quite rigid (and strong) for its weight and might be one decent possibility. More simple is just adding mass, say with dynamat.

[rockerbox]

My Chalet has a large storage area over the generator and the ceiling of the storage area is the floor of the bedroom. However, the bed is elevated above the floor and this space is where the water tank is located. So it is like sleeping on top of two drums ! The generator cover top is very close to the floor of the storage area and the support frame is suspended from this storage compartment floor. I'll need to find some thin sound absorbing material to slip in that narrow space, but I guess what ever I can find will help some.

I have already glued heat reflective material to line the storage area to keep heat in the RV. Perhaps if I glued a layer of sound absorbing material as a new storage compartment liner will help to absorb both vibration and noise. Does that sound reasonable?

[Gjac]

If your genset is under your bed like mine you probably have space between the top of your genset cover and the under side of your bed. I store blankets, pillows etc in this space and around the sides of the cover. The only reason I run the genset at night is to use the AC. The AC makes more noise than the genset now. I do feel a slight vibration but no noise. A layer of lead sheeting bonded to the inside of the genset compartment would be another way to reduce noise inside the bed room. 6 ins of blankets etc on top and 12 ins on the side of pillows will insulate sound more than 1/2- 1 in of acoustical foam. At least that is my experience.

[nayther]

Check that something is not grounding out the generator, meaning rigid connection between generator and MH. Low frequencies are attenuated with mass, higher frequencies can be reduced by insulation such as the Dynamat or duct liner or duct board.

[DrewE]

It may help to think about the difference between sound absorption and deadening, which are not (generally) the same thing. Dynamat and similar products work not by absorbing sound but by adding mass and possibly stiffness to the surface, so it absorbs and vibrates and transmits sound less. It's blocking sound, but not absorbing it to any great degree. Acoustic foam, on the other hand, absorbs the sound; it damps out the vibrations in the air.

If your noise is being transmitted mainly the generator vibrating the structure of the RV and then it vibrating and making noise, then sound absorption materials around the generator aren't going to have much effect at all. Deadening the walls etc. that are vibrating will help, as would improving the mounting so less vibration is transmitted.

If you do put foam or other materials around the generator compartment, make sure they are noncombustible, can take the heat, and are compatible with gasoline and similar chemicals. Many acoustic foams and similar products would not be prudent to use in such an application. Others are fine, of course.

For the coset walls, if they're constructed like the interior walls in my RV, stiffening them by adding some more framework inside or building a sandwich with rigid foam board would help a whole lot. Mine are just thin luan or something similar attached to studding, which can act something like a drum head or flapping tarp.

[rockerbox]

Vintage 465.

How did you use the duct liner - to surround the generator? I have two closet walls on either side of the head of the bed. I imagine that I could lower the vibration and noise transmitted through those structures with duct liner or other sound absorbing panels. At the moment, I think the closets are functioning like a musical drum when the generator is running.

[Vintage465]

As mentioned earlier, make sure it is isolated regarding the mounting. In reality it is likely isolated as far as mounting goes, but you may need to improve upon that. Also, I've used duct liner from Heating and A/C shops for many years to use as sound deadening. Comes in 1/2" and 1" thicknesses. HVAC shops will also likely have the stick on pins to help hold it in place til the contact cement sets. Another option, though possibly pricey-er would be to use the high density foam that is used to make "ergo-pads". That stuff would work great, though I'm not sure how you'd source enough of it in sizes large enough for the compartment that wouldn't leave your wallet hemorrhaging. Then there is always the possibility of different options to get thru the night w/o the unit running

[D_E_Bishop]

I don't know how large a inverter generator you can buy,but there are several 3kw inverters on the market, some even have electric start. Why not look into replacing the Onan with, say a Champion with electric start? If the size is compareable it would seem to be a win - win. Quieter, less vibration and can be rigged to use the coach's fuel tank. Then everybody would wonder how you got it to be so quiet.

[rockerbox]

I have used the foam ear plugs in the past and have had some success; depended on how fatigued I was.

Also, the extra battery is an option; The E450 supposedly has a chassis location to mount one near the V10 under the forward right side of the chassis. Designed for a second engine battery, but could be wired to run the DC fan circuit. The long wire run would probably require a larger gage to insure minimum voltage drop when powering the fan.

The A/C noise is more of an "air movement" noise and for me, not as annoying as the generator.

I checked the link provided by Joe for soundproof cow.com. That product includes a liquid material to coat structures and absorbs noise and vibration. I might coat the outer shell of the generator and see if that helps.

[camperdave]

You could buy a new battery so you can run the heater through the night without the generator.

Wouldn't help with AC, but the AC is usually louder than the generator anyway.

[JimBollman]

I find the wax style ear plugs that are very effective. I always keep a box of them in the camper by the bed. They come in handy for other peoples generators as well as our own and a wife that occasionally cuts logs wth a chain saw in her sleep.

[rockerbox]

Yesterday I did a Bing search for "noise cancelling ear plugs" and learned that several companies including Bose sell "noise masking" and "noise cancelling" ear buds that are practical for use when sleeping. I knew that aviation headsets had this technology but had no Idea that the technology is now small enough for ear plugs. These are "active" devices with miniature batteries.

This may be the simplest solution yet.

[DrewE]

4x4ord wrote:
Sell the generator and get a Honda 3000 that you carry on the back of your truck.

The OP has a class C motorhome. There likely is no truck involved to carry a Honda 3000 watt generator in...and even if there was, it would not be sipping fuel from the big motorhome tank but need filling more or less frequently.