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Old 09-16-2021, 12:27 AM   #1
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Generator noise cage re-insulation

The lining material on the inner face of the generator noise cage is completely gone/worn out. It has dried out and I find pieces of it throughout the engine room.

I was thinking of finding an appropriate replacement material and reconstituting that inner lining. I am looking for comments or advice of what might be a good replacement material. I find most of the available stuff also insulates heat which I think would not be ideal for the generator.. if any heat stays in, it might overheat the generator. Could something like Soundown undercarpet material be an option? I am planning to install the 1Ē standard soundown in the engine room but it does look to be too thick for lining the generator cage.

Any advice or comments would be much appreciated.

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Old 09-16-2021, 06:54 AM   #2
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Carpet underlayment should be used under carpeting. It is missing a component (absorption layer) to be a good generator enclosure insulation.

You should use a 1" thick vinyl/foam insulation with a 1lb sq ft vinyl barrier. For generator enclosures the peel and stick option really helps getting the insulation under the bent "lips" around the perimeter on the back of the panels. "Better" insulation will usually not contribute to an overall noise reduction. The air intake opening kind of sets the baseline for noise, and better/more baffling is the only way to improve this noise "leak."

All insulation either acoustic or thermal, will have a thermal component. Your generator is designed to accommodate an enclosure, the air intake baffle is at the generator end so "outside air" flows over the gen side before the intake manifold. The engine is water cooled and doesn't care.

There is better insulation, but for smaller generators like yours 1" 1lb is the best compromise. You probably don't have room for a thicker product, and a heavier (2lb sq ft) barrier makes the panels very heavy and create the need for mechanical fasteners. As I mentioned above, better performing insulation typically doesn't improve overall noise reduction.

Two other options that do work are secondary isolation and a gas/water separator in the exhaust run.

Secondary isolation calls for an additional set of mounts under the generator in addition to the factory mounts.

A gas/water separator will reduce exhaust noise

https://www.centekmarine.com/products/

Isolators need to be sized for weight properly, your generator most probably has the mounting holes placed to equally distribute the weight around the C/G, the manufacturer accounted for this option.

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Old 09-16-2021, 08:01 AM   #3
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We relined our generator enclosure with this and the difference was amazing!
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 09-16-2021, 08:36 AM   #4
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The product John used is what the marine industry calls acoustic foam. It is an absorber, but has no barrier. The description says 21 sq ft and the total weight 2.2 lbs.

Mass is what stops noise. Imagine having a conversation with someone, and a wall of this foam is installed between you. Now imagine an 8" concrete block wall instead of foam.

Foam absorbs noise, and will reduce noise inside the enclosure by reducing the increase in noise from reverberation against the solid panels of the enclosure. This reduces the noise outside the enclosure.

By incorporating a decoupled mass layer as a noise barrier you increase the performance of the noise reduction by a massive amount.

I will add that most generator manufacturers install acoustic foam in their smaller generators, say 50Kw and down. A vinyl/foam insulation will provide much better performance than the OEP product in most smaller generators.




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Originally Posted by JohnEasley View Post
We relined our generator enclosure with this and the difference was amazing!
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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Old 09-20-2021, 10:36 PM   #5
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Thank you all for the great information and comments. Armed with the above comments, I also spoke with Soundown. As stated above they recommended the 1” sound barrier fir the generator cage. And the 1.5 or 2” for the engine room ceiling. I am debating ordering Soundown material for the entire engine room and a lighter material for the generator cage. They recommended removing all sound/heat ceiling material in the ER and replacing what I have with their material. The installation would require screwing the Soundown into the exposed wood surface in the ERA ceiling. I am not keen on removing my current ceiling insulation..maybe I can glue the Soundown to my ceiling material and run their Mylar tape around the edges to hold it up just in case.

Thank you very much for the help.

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Old 09-20-2021, 10:47 PM   #6
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My order of Soundown 2Ē 2 pound insulation came a couple of days ago. I am using the PSA to help hold it on along with the glue on insulation hangers. I may also use some self tapping screws with large fender washers in some places. I am going to remove the existing insulation since it doesnít have any mass in the middle but is just foam. The loaded vinyl in the insulation is indeed the key to stopping the noise.
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