Making an engine bay quieter

[DeanS]

Any ideas on the best way to quieten the engine space....

 

The ideas I'm playing with are:

 

1. Thick rubber matting on the stern area to stop the sound coming up through airgaps in the engine deck boards.

2. glue a 2" wall of soundproofing foam on the inside wall of the engine room which transmits sound into the boat living area.

 

Anyone done anything similar?

[Tonka]

turn the engine off

[Neil2]

It's amazing what can be done with proper soundproofing. We shared locks with a boat a few years back that had the same engine as ours, yet it was hardly audible by comparison. The owners had fitted a hospital silencer and some very heavy soundproofing under the cockpit deck - you need mass to absorb sound, so the heavier the material the better - the lead sandwich stuff is what you want but it is very expensive.

[DeanS]

I worked in a sound studio once...and it was all about air gaps. If you have one, sound gets out. What is "lead sandwich"?

[Ex- Member]

I like a noisy engine LOL It also lets people know i'm there LOL

[FredW]

Hi,

We gave some thought to soundproofing our engine bay & found this company. http://www.noisekiller.co.uk/

Spoke to them about delivery but in the end decided the noise wasn't too bad so didn't bother. Their product came highly recommended.

Fred.

[Kwacker]

I lined the engine bay with specialist soundproofing http://www.acoustafoam.com/eshop.php?productID=6099&licenseKey=f7879cdc8a03d7d226c6c0604f19de41 (fireproof, multi-layer, PU faced) then had an hospital silencer fitted.

All you can hear now is a bit of the diesel "clatter" and the sound of the water around the prop.

I'm working on killing the remaining high frequency noise ... I want electric motor quiet.

 

I'm still amazed when I have the engine cover lifted with the engine running just how much noise there is in there, but the foam does a really good job.

 

Most of the noise on the boat now is outside the engine bay, and caused by things resonating in sympathy with the engine's vibrations ..... and my guitar.

Edited September 7, 2013 by Kwacker

[Trento]

Dean,

By now you know what "lead sandwich" is/are.. But for cheapness, beg borrow, or steal as many egg trays as you can. Paint them with a fire proof paint(it also give rigidity to the tray) and fix them where you feel appropriate. I built a 3 sided box and a top around the engine.. Stuck the trays on the inside...Works a treat.

[Neil2]

I'm not an expert in this field, but there is a difference between cutting out resonance, which you can do with "soft" materials such as foam, egg boxes, whatever, and preventing sound from escaping which needs mass. Lead is still used in soundproofing because it is so dense, ie you don't need a huge thickness to create a lot of mass.

[nbfiresprite]

You could always replace the engine with a horse.

[Higgs]

A few hours of engine noise can start to wear you down. It does me, anyway. The BMC in my boat isn't a modern engine and I have fitted the acousta type foam to the boxing around the engine. Not complete yet, but it is doing the job. Getting jobs done these days is a lot harder now that I no longer work at a boatyard, with all the workshop at hand.

 

Don't see why everyone sitting at the front of the boat should have all the peace and quiet to hear the sounds around, especially in the countryside.

Edited September 8, 2013 by Higgs

[Psycloud]

Never even thought about this until this thread appeared but when we went out for 2 days cruising last weekend it did get a bit tiresome having to shout at each other over the noise, misunderstandings, not being able to hear other passing boaters and gongoozlers talking to us without dropping into neutral.

 

We have a cruise stern and the decking took pretty much 2 8x4 sheets of hexagrip to cover it so would need the same amount of acoustic foam. Question is: what thickness would be sufficient to reduce the noise from a Bukh Diesel engine enough to be able to talk at normal volume? Also, would I also need to stick it to the sides of the compartment or just under the deck boards?

[Higgs]

Never even thought about this until this thread appeared but when we went out for 2 days cruising last weekend it did get a bit tiresome having to shout at each other over the noise, misunderstandings, not being able to hear other passing boaters and gongoozlers talking to us without dropping into neutral.

 

We have a cruise stern and the decking took pretty much 2 8x4 sheets of hexagrip to cover it so would need the same amount of acoustic foam. Question is: what thickness would be sufficient to reduce the noise from a Bukh Diesel engine enough to be able to talk at normal volume? Also, would I also need to stick it to the sides of the compartment or just under the deck boards?

 

 

The Acousta foam I've seen and used is about 2" thick and is a sandwich of dense material and foam. Some of these types vary in density and weight, this may be a quality aspect. Some are foil-faced on the surface that faces outwards.

 

Any surface that you can deaden will be a gain in noise reduction, but in an engine room/space this might not be possible in some areas. Not sure how much you would need. Start with the deckboards and also soften the the contact points that the boards sit on to stop any rattling.

 

If there's space, fit a hospital silencer.

[mrsmelly]

You could always replace the engine with a horse.

Dont think his engine room is big enough.

 

Tim

[Higgs]

You could always replace the engine with a horse.

 

Ah, you will need a horsepital silencer then.

[Kwacker]

They don't recommend the use of the heavier multi-layered foam on the deck underside as the spray glue they supply won't hold the weight, so I used a lighter 2" foam under the engine cover, and fitted rubber seals (from a dishwasher) to bed the cover to the deck. I couldn't put a seal all round, as the engine room is not ventilated, leaving air gaps so the engine can breath.

The heavier multi-layered foam was used on the larger vertical surfaces, especially the front bulkhead.

I haven't covered everything by any means, the floor is uncovered, as are the large areas around the silencer, weed hatch and batteries. I was going to cover everything, but it just didn't need it. The whole job took about an hour., and made conversation much easier.

The real difference was having the hospital silencer fitted though.

We can have a whispered conversation with the engine at 1600 revs underneath us, makes long distance cruising a joy, and the wildlife doesn't scarper before you arrive.

 

ps don't waste your time with egg cartons.

Edited September 8, 2013 by Kwacker

[Québec]

There's various products available, especially in the DIY/pimp your car/truck market. Some ridiculously expensive. From past experience of genuine sound-proofing experts - we were building sound studios and wood/metal working workshops in closer proximity than we would have liked - you've got to deal with high frequency and low frequency sounds, and also vibration both cause (note Kwacker's rubber seals) and effect i.e. loose anything.

[Neil2]

Interestingly I was on a boat recently (cruiser stern) that had a wet exhaust, and a huge amount of ballast, mostly concrete blocks, in the engine room. There was no soundproofing of any kind and the deck boards were a very loose fit, yet this was one of the quietest boats I've ever come across. I would like to have known which was the more telling factor, the wet exhaust or the extra material. I do remember coming across an old Springer with an air cooled Lister which was a lot quieter than I expected, that boat also had a lot of concrete in the stern.

 

Concrete blocks are a lot cheaper than lead lined soundproofing...

 

 

[Naughty Cal]

Our engine bay lid has a thick layer of sound deadening on it and it is surprising how much difference it really makes.

 

Obviously doesn't stop all of the noise and at high speeds the turbo whistle is very vocal. Dread to think how bad it would be without the sound deadening material!

[Biggles]

Have a look at my blog. Use the search for a link to sound proofing. On a mobile so can't do a search atm

[Guest]

I turn my hearing aids off when cruising, the effect is stunning. I can still faintly hear a whine from the transmission but nothing else. Electrically powered boats must be brilliant. I often wondered about a diesel genny at the front powering an electric motor at the back, or a hydraulic setup.

[ditchcrawler]

This is the stuff http://www.asap-supplies.com/marine/marine-soundproofing-and-noise-reduction-standard/quietlife-soundproofing-noise-insulation-and-noise-deadening-products-801434

[PaulD]

They don't recommend the use of the heavier multi-layered foam on the deck underside as the spray glue they supply won't hold the weight, so I used a lighter 2" foam under the engine cover, and fitted rubber seals (from a dishwasher) to bed the cover to the deck. I couldn't put a seal all round, as the engine room is not ventilated, leaving air gaps so the engine can breath.

The heavier multi-layered foam was used on the larger vertical surfaces, especially the front bulkhead.

I haven't covered everything by any means, the floor is uncovered, as are the large areas around the silencer, weed hatch and batteries. I was going to cover everything, but it just didn't need it. The whole job took about an hour., and made conversation much easier.

The real difference was having the hospital silencer fitted though.

We can have a whispered conversation with the engine at 1600 revs underneath us, makes long distance cruising a joy, and the wildlife doesn't scarper before you arrive.

 

ps don't waste your time with egg cartons.

Evo stik carpet adhesive spray is much better than the stuff supplied with my "Quietlife" foam. Evo stik is actually stronger than the foam which can delaminate if roughly handled. I added a few angle strips as belt and braces.

 

Insulating under the deck with proper multi layer foam is well worth the effort and it made a huge difference to noise levels on our semi trad deck.

 

Most of the noise in the cabin seems to be transmitted through the steelwork and insulating the bulkhead didn't make much difference. Any suggestions?

 

Paul

[Biggles]

I'm on a lappy now so here is the link to my sound proofing.

 

http://boatbuildblog.blogspot.co.uk/2012/08/a-kind-of-hush.html

[Ally]

We're building 'bisbigliando' currently, meaning whispering (harps) so mega hospital silencer & acoustic insulation throughout the engine bay