Best soundproofing material for engine compartment?

[ferrailleur]

Is there anything fireproof rather thin and easy to work with?
Thanks

[GordMay]

No.
Marine engine noise level tends to concentrate in the low to mid frequency range, typically 125Hz to 2,000Hz. In addition, there is low frequency structure vibration related noise.
The ratings for classifying and comparing the various sound-proofing materials are:
- NRC, the noise reduction coefficient, which is for absorbers. The NRC rating is between 0 and 1 and its an average of how absorptive a material can be at these four frequencies - 250, 500, 1000 and 2000. NRC measures how well materials stop sound from reflecting, as a percentage of sound that a surface absorbs.
and
- STC, the sound transmission class, which is for blockers. STC is a measure of how well a material blocks sound. The higher the rating the better. You can improve the STC of a wall by building it from a more dense material (sound insulation improves by about 5 decibels for every doubling of mass), by adding an air gap, or by adding sound absorbing material.
In countries outside the North America, SRI (Sound Reduction Index), describing an improvement of so many decibels (dB) sound reduction, is a more common measurement.

[WSMFP]

Yes, this company makes a number of sound deadening and machinery space insulation.

https://soundown.com/application-sys...space-systems/

[Sailmonkey]

Define “thin” and “easy to work with”.

[ferrailleur]

Originally Posted by Sailmonkey

Define “thin” and “easy to work with”.

one inch thick and easy to cut to size and apply on...

[Sailmonkey]

Originally Posted by ferrailleur

one inch thick and easy to cut to size and apply on...

This is among my favorite stuff.

Wipes clean, cuts with a knife. Glue and screw installation.

https://www.defender.com/product.jsp...105&id=3018333

[Lepke]

Lead sheets. Not cheap but stop sound well and not flammable.

[Montanan]

Originally Posted by Lepke

Lead sheets. Not cheap but stop sound well and not flammable.

You will find this used in many sound studios and is readily available from many sources. Although you may wish to pick it up from the retailer as it is heavy as lead and thus tends to be pricey to ship via UPS or FedEx or postal service. Lead can also be integrated as a mass loading to vinyl in rolls or sheets.

It is often layered with other sound transmission loss [STC] materials as adhevise bonded laminates, e.g., between sheetrock, or plywood.

"Sheet Lead as a Barrier – The effectiveness of any barrier to noise transmission is established by three factors.
1. Mass – The greater the weight per square foot of barrier, the more sound it can block.

2. Limpness – A limp material blocks sound over a wider range than a rigid material, which can radiate the sound.

3. Integrity – There must not be a path through or around a barrier.

Sheet lead is heavy. Its high surface density (59 lb./sq. ft. per inch of thickness) will provide more of a sound barrier than a considerably thicker layer of plaster, glass or concrete. There is a point at which these other materials will gain stiffness that negates the effectiveness of their density.

Because of its inherent limpness, or softness, lead cannot be easily set in vibration. It does not resonate or “ring,” hence it cannot radiate sound.

Being a metal, sheet lead has an advantage over various aggregate materials, since it is more uniform in density throughout. Also, its softness allows it to be easily cut, folded, formed or crimped. This allows sheet lead to have the flexibility required to insure the integrity of the barrier system.

Thus, sheet lead meets all the criteria for a good barrier. This, coupled with the fact that it can be readily adhered or fastened to other materials for structural or sound absorption purposes, facilitates the development of effective noise control systems.



"Lead has a high surface density and is correspondingly heavy. It can provide a very effective sound barrier compared to plaster, glass, concrete or many other materials. Also many other materials tend to become more rigid as they become thicker, rigid materials do not make good sound insulators since they can retransmit sound though vibration and resonances.

Lead, on the other hand, is soft and malleable. This makes it impossible to radiate sound and very difficult to be set into vibration, and has the flexibility needed to make a good sound barrier. Since lead is a metal it has a uniform density compared with wood and other materials and finally it is easy to attach lead sheets to other materials to produce structurally sound walls.

In addition to sheet lead, it can also be used as an effective sound barrier in leaded plastics or in lead sheet rock, to block airborne noise or to dampen the ringing of metal structures such as steel decking or panels.

An absorbing material such as lead sheet absorbs sound by spontaneously converting part of the sound energy to a very small amount of heat in the lead.

Lead sheet’s effectiveness as a soundproofing material can be seen in the table below. Lead sheets provide noise absorption over 10 times more glass or concrete and up to a 100 times more absorbent than wood."

Just don't eat off of it!

Also good for absorbing radiation and you could melt it to add to your keel weight.

[model 10]

Aircraft are crazy about weight but some small aircraft have lead firewall blankets. It's so loud inside, it's worth the weight.

I think somebody should sell a noise cancelling speaker set up for a sailboat. I don't need to hear the damn engine. I have alarms etc.

[Montanan]

References:

https://www.practical-sailor.com/blog/-10720-1.html

https://www.nkgroup.co.uk/file/2014/...YM-article.pdf

[SailRedemption]

We used 1'x1'x1" square tiles from Sailor Solutions. Simple to cut, peel and stick adhesive backed tiles. They work pretty well on our boat. Engine is pretty quiet when we motor. Just need to stop rattles around the boat now.

https://sailorssolutions.com/index.a...ategory=Engine