sound insulation

[Guest]

hi, whats the best sound insulation for around the engine bay and where is it available. i want the best deal for my buck as well. cheers

[wheels 543]

Sound has been a big part of my proffesional life. So I am probably the most qualified to say that the world of sound insulation is a mine field of ideas and products and opinions.

So I am not going to say this following product is the best. it is one of many available. However, it is a product I have used and do consider very good and my personal opinion is that it is the or at least one of the best.

http://www.acoustop.com/ There are possibly other products of the same design out there, so Acoustop may not be the end all for this type of material.

This is what i believe you need to look for in a product.

First of all, there are two different ways of reducing sound and all products do this in one way or the other. Either Sound Isolation or Sound absorbtion. Yes there is a difference. Lets come back to those two points.

First of all, there are three essential points you need to cover for an engine room. Normal Engine Heat, Oil and Fire. So you need a product that has a reflective foil and in a decent thickness. This means the material below is protected from all three things. There are products with a thin mylar film I feel is useless an to the other extreme, products with heavy foil and fire retardent material below that, which means expensive.

The next point is the Frequency to be isolated. No one product treats all frequencies. Although some products cover a range that fits most of the problem ones, they don't do as well as the ones designed to cover a specific noise. You will find that the ones designed to cover a range tend to be physically thick and often difficult to fit in confined engine rooms. The thicker that product, the more sound that is absorbed. The products that are designed for specific noses are thinner more compact and have the greatest attenuation for that problem noise range. Acoustop has a product for Petrol engines and Diesel engines seperately.

Right, now back to the first point I made. Sound absorbtion is done by simply "muffeling" the sound. The thicker the product, the better the attentuation. Sound Isolation is a different thing completely and is engineered to take care of certain sounds. It works like this. Sound is a wave length. This wave travels through the surface material and into an acoustic foam of a specific thickness. This thickness is calculated for the wave length. Now wave lengths are measured in metres. But equal parts of a waves length forced back on themselvs can create cancellation. So the wave length travels through the first bit of foam and then hits a very dense barrier. Lead used to be used for this and it is possible that a product may still exist that still uses lead. Barrium Oxide was introduced many years ago as being a better material. The dense layer takes energy to make it move and the sound thus is spent trying to make the barrier move. The movement is then isolated from the wall by another foam layer on the other side of the dense layer. The layer vibrates in the foam and what is not absorbed in the dense layer gets reflected back into the foam and back against the sound wave and helps in reducing it also. The same thing happens on the other side of the layer. So the result is being able to reduce an enormous amount of sound power in a very thin material. But as you can imagine, it is expensive. If you want the best bang for buck, this is the way to go. It will cost more but give you the best result for the least amount of space taken up.

I hope that helps. Probably not as far as the wallet is concerned.

[Rhys 0]

Wow Wheels, that’s a pretty detailed answer! From a practical point of view it’s worth remembering that you’ve got a thumping great diesel engine banging away inside a drum so regardless of what remedial actions you go for, the engine will always be audible. It comes down to bang for buck. Acoustop (from Formans), Wavebar (from Volpower/Potters) are two good examples on products to line the engine bay with. They have a bit of density and some absorption but just as important they have a protective (shiny aluminium looking) surface in case of oil spills and they are quite ductile so they can be bent to fit the curve of the hull and in all nooks and crannies. (While the heavier 8kg/m2 is better for nosie, it can be difficult to bend about small radiuses so the lighter 4kg/m2 would be a better bet. This stuff ain’t cheap.

The other thing to consider is vibration isolation, ie reducing the amount of vibration that the engine is imparting into the hull (which then resonates) in a similar way to the engine mounts in your car. An engine supplier should be able to help with this. Remember that it’s not only the engine mounts that require isolation but also anything that’s rigidly attached to the engine and hull.

[ScottiE 174]

Rhys - you always told me concrete was best!

[Guest]

hi, whats the best sound insulation for around the engine bay and where is it available. i want the best deal for my buck as well. cheers

 

Hall Spars

Sheldon Spars

North Sails

Fyfe Sails

 

A lot of choices really

[Guest]

That Acoustop stuff Wheels talked about is great stuff, had that fitted to an engine room some time back, (Barrier Wrap, had a foil sheet on one side) The only problem is the clown that installed it put the foil to the bulkhead This meant that when you were in your cabin sleeping the 2x 12V71 Gm's could not hear you snore.

 

By time it was all stripped out and done correctly, man what a difference

[wheels 543]

I have a dirty great Perkins 6.354 right under the Pilot House floor. I don't have the room completely insulated yet because it is so darn big. working on it in small affordable doeses. I had a Launch guy on board one day when I aws running the engine and he was stunned at how quite the thing was. The engine is solid mounted to the runners, so even though she's a large tank and directlky coupled, you can still have a quite conversation in the Pilot House while at full revs.

[tuffyluffy 76]

The Acoustop stuff is good, but a bit of a rip-off price-wise IMO - it was going to cost me $600+ to do my small engine bay.

 

So I re-lined in a commercial product from Autodec (http://www.autodec.co.nz) and its worked a treat and was 1/4 the price of Acoustop. Its the same stuff they line truck engine bays with, and its hushed my little Volvo down quite nicely.

[Young Entertainer 59]

have seen the autodec stuff in action and it is pretty good, especially as it doesn't have the word marine attached to to it so the price is reasonable

[wheels 543]

Acoustop is expensive because engeneerting wise, it is a complex product to make. The barium oxide is also expensive stuff. It just comes down to what result you want. Yes it is expensive. There is no other product better unless it is the same type of product. I believe someone may still be making the Lead one, but i don't know who.

Acoustop was never made just for the marine market. Their product range is huge. They make all kinds of sound absorbing linings and coverings and even a paint type coating designed to deaden Steel plate.

There is also a product that looks like Hollowfill fibre with a Foil covering. This also works OK, but the material is ranges from 50mm to 100mm thick and sometimes you don't have that kind of room spare. Plus I am not sure i like the idea of that stuff in an engine room in case of fire. But a friend of mine has just installed it in his. It is a fraction of the price. once again, not as good though.

By the way, we had a box lined with the stuff and a Radio set to 11 on the dial. The box was over the radio and you could hardly hear it. The customner would see hte box, we would give a brief discussion about it and then suggest they lift the box. The result was getting one hell of a fright.

Oh and also, if you get any material that requires gluing, do not use F2 glue. it will eventually fall off. Acoustop sell a glue for their product and the sheets come pre glued. You need to use a glue that can stand the heat and Oil fumes. Ados do make one, just can't remember number. Bostick also make one. Just make sure it is heat resistant.

[Noodles 0]

what about dynamat. seen it used on a harvester. works a treat so im told

[wheels 543]

What we are seeing in this thread is what I expected at the beginning. There is a huge variety of products and opinions. And it becomes even more so, opinion wise, once you start talking to suppliers. So to help make a decision, beyond the construction of the material, you need to understand a couple of key points.

If any material is worth a damn, then it should have some published specs. What you need to look for is two key hand un hand points. Watch for those that skew these two points. You need to know the Frequency range it is designed to reduce and you need to know by how much. That "how much" should be measured in dB (decibels). A note here, for every 3dB, our ears percieve that as double the sound. 6dB = double the power required to produce that sound. So if you have an engine that produces for say, 100dB (that's really loud) and you reduce that sound to 97dB, then you percieve that has half as loud. (97dB would stiull require Earmuffs) So you should be able to ask the supplier for a graph or some spec that say how much the sound is reduced by the material. But the other key point is the frequency that the material is good at reducing. No one material can reduce everything. Some materials are beter at certain sounds than others. Diesel's produce lots of low sounds, so you need a material that can take care of low sounds. It is very easy to reduce high freq sounds, but progressively harder to reduce low feq sounds. So don't get fooled by a spec that does not give you any numbers, only a squiggly looking line that shows a real dip somewhere, but does not tell you what the where is. Or that is may show a real big dip up the top end of a graph. But here is another little curly one. They may simply say, it gives you a sound reduction of -10dB. And that may well be true. But the -10dB may well be at some frequency that you are not trying to control anyway and the very freq. that you are may only have 3dB. Why am I saying all this?? because the materials are damn expensive and you want to get the best bang for your money and some materials are just not worth the money, even though they are cheap.

 

Now.....If you want to go real cheap, here is a real cheap alternative, that works not toooo bad. Go to your local M10/mega or Supercheap or similar and buy an arm full of Car windshield Sun visors that have the silver foil on them. You usually pay $3-$5 bucks for them. Now see if you can get hold of some fibreglass bats from a biulder mate. The sound ones are even better. Or, you can also use the Foam carpet underlay. Staple or glue that around you engine box and then the same with the Sunshields to insulate and protect from oil and heat. To maintian the thickness, you can also use a longish screw and washer and just screw in part way, so as the thickness of the material is maintained, but the screw holds the material. It works as well if not better than some of the other cheaper end products available.

[Atom Ant 0]

Wheels you're bloody brilliant m8! Love that last one. I may not use it but I love hearing about ingenious ways to do stuff. It confirms my opinion that I don't need to know anything, I just need to know how to get hold of you! The insulation spend is gonna depend on the boat too I guess. If you have a nice flash high end boat then doing the batts and windscreen shield thing would be a no no, but if you have an ... ahem ... older and lower valued vessel then this sort of thing is just the ducks nuts!

[Guest]

Someone was raving to me about the sound deadening properties of the rockboard fire insulation panel that you put round the back of the wood burner to stop the Gib catching fire.

Not a lightweight option though.

[wheels 543]

It confirms my opinion that I don't need to know anything, I just need to know how to get hold of you!

Arrr, but what if I'm wrong. You will never know

 

When I was in sound, I was part of a top Proffesional Live Audio BB. It was common to have people you had never heard of put in their two cents as if they were Gods gift to live sound and had been there and done everything. One the the top guys had a caption at the bottom of his posts, "no one can here you mix on the internet". And that summed it up. You could have guy's spout on about all their achievement, but in the end it comes down to, "can they really do it??? and "Well none of us can never really know because we won't get to hear them, so take all comments with a grain of salt unless you really know them". Hmm, that's a big nustsehll.

Of course the ones that really had been there and done everything new the real truth and it wouldn't be long before these newb's got shot down.

But the same applies here, you can ones like me spout on and sound like they know everything, but the reader will never really ever get to know. So you do have to weigh up all advise with other posts and take a common theme, unless a poster can back up what they say. And eventually a poster of long standing can biuld up some credibility because the ones that really do know, will eventually shoot the teller oif the tall tales down.

Please note: I hope I never become pompous enough to never stand for correction. I may share my own knowledge, but I will always stand for correction if someone has a better way, idea or knowledge.

[Atom Ant 0]

Don't worry Wheels, U da Man

[Guest]

Please note: I hope I never become pompous enough to never stand for correction.

Or in an election

 

but I will always stand for correction if someone has a better way, idea or knowledge.

Ah, so even if you did you'd be no good at it :)

[wheels 543]

I'm way too hinest to make a politician. And I can't stand Kissing Babies, nor do I like Sweets all that much, so I wouldn't steal from them either.

[Guest]

thanks guys, awesome feedback wisdom and humour. saves me having to listen to some bullshiting sales rep.

[Rhys 0]

Someone was raving to me about the sound deadening properties of the rockboard fire insulation panel that you put round the back of the wood burner to stop the Gib catching fire.

Not a lightweight option though.

 

Slacko

 

The reason that this performs so well is its density, which is great for controlling the transmission of noise, say between the engine room and saloon. While it’ll outperform the Acoustop in that respect, it would be a mission to fit retrospectively, which is where the Acoustop wins hands down. What it doesn’t do is absorb noise in the engine room (reducing noise at source reduces noise at receiver). The Acoustop has a foam layer bonded to the vinyl, which while an average absorber, is robust enough for an engine room and way better than a lump of fire board.

 

Dynamat is relatively light compared to the loaded vinyls so it wouldn’t be a great substitution. As it’s so thin, it wouldn’t be a great absorber either.