Run the exhaust from a generator into a bucket of water.
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This is not a direct answer to your question. LOL

I found on my Honda 2000 that the engine noise was louder than the exhaust noise.

This was just done by ear.

Bill K

I read some where that you should not make ajustments to original generator mufler systems. I don,t know why.

My sailboat runs it's gas motor exhaust (basically an old tractor motor) through water. And it runs poorly without the water. Water adds quite a bit of back pressure and the engine needs to be tuned to run that way. I suspect the generator would run poorly.

It is generally the carburator/engine of a generator that make the most noise. However some do have loud mufflers. Look at the housing of a Honda or Yamaha inverter generator and see how they have muffled the noise. Basically you need foam for the noise and a fan to exhaust the engine heat.

I think it will sound like a motorboat. Budda Bladda bladda buda bladda.

I read once where a person made a box that went over the gen and used it for additional sound dampening. They installed a fan in one end so it would get enough freash air and ofcourse kept the exhaust end away from flamable stuff so it would not catch on fire.

Not a real good idea unless a check valve is added in the system. When the engine is shut off cold water could be drawn back up into the engine with disastrous results.

I'd buy a quieter Gen..........Bruce

Given the photo posted, he already HAS possibly the quietest generator on the market, so that doesn't seem probable.

I have seen quite noisy generators placed in open-topped boxes about 50 lined inside with 3" or 4" thick foam and the noise level (except almost directly ABOVE the unit) is incredibly quieter.

The box in reality only needs to be 4 sides, with no top OR bottom, and the sides can be carried as a stack, and assembled on-site for easy transport.

Just leave about a foot in all directions from the generator so it can "breathe" and get cooling air.

This works with most all modern 3600rpm generators that are moderately muffled to begin with, the final result being that they are almost as quiet as the inverter Hondas for a small fraction of the price. I have a Honda 2000ui, but my "boxed" 6.5hp 3500watt Chinese generator is darned near as quiet from 25ft as is my "un-boxed" Honda.

Bob

BTW, I don't think you'd hurt your Honda by directing the exhaust into a bucket as shown. Just make sure the generator exhaust is above the water level, and drill a small hole (1/8" or so) in the vertical portion of the tubing above the water level to preclude developing negative pressure that could cause water being drawn back into the engine. Very little exhaust or sound will come from the hole, BTW.

The box idea sounds PERFECT.

Please understand that marine exhaust systems are designed for marine engines. If you apply any backpressure to a small engine (such as those commonly found on gen-sets, lawnmowers, etc.), you will cause incomplete combustion, more pollution (from the incomplete combustion), fouled spark plugs, dirty cylinders, and you also risk burning up your exhaust valves.

The best solution has already been mentioned above...shielding with sound proof or sound dampening insulation. Be careful also when shielding your gen-set that you provide adequate ventilation (engines need to breathe in just like we do, so don't starve it for air) and don't put your insulation too close to the muffler/exhaust components as this could become a fire hazard.