sound proofing

[Oldad]

I am building a version of Ninegret and want to soundproof my engine compartment. I am sure that everybody is familiar with Ninegret but just in case it is a 22 foot picnic type boat with the outboard motor in an enclosed well. I want to sound proof the engine compartment. West Marine sells a kit with one inch foam sound deadening material that covers 12 sq ft for $139. I would need about 3 kits. Looking for an "outside the box solution. Any ideas?
Oldad

[wizbang 13]

remove the well and put the ob on the transom, or even better, 2' aft of the transom on a brackett.
sorry, that is not what you want to hear. but outboards in a well make more noise, vibration, weight, smell and cost.

[keyhavenpotterer]

Hi,

I've been making a campervan this winter and had to look at sound deadening and insulation.

It has to be multi layered. You can block sound with things like Dynamat, but its quite expensive depending on how much you need. A cheap alternative used here is thin lead flashband from builders merchants. It sticks on once the film is peeled off and comes in rolls. Pretty much same as dynamat by all acounts and alot cheaper.

Next is a usually closed cell foam with or without a rubber membrane attached to it. Lots of choice here too from audio sound insulation companies & builders use it between the walls of flats/ apartments to reduce sound transmission or under floors etc. Some people use closed cell foam camping mats as its on a roll and cheap too. A natural choice used by many campers here in the UK is Welsh mountain sheeps wool compressed into bats or a dense roll or wad. It thermally insulates but because of its density sound insulates well too. Its fireproof too. A wooden box will go along way too made from dense timber. Fire retardancy would have to be considered.

Modern four strokes are very very quiet though, that would help reduce any noise in the first place, you can barely tell their running.

Not so useful, but this company in the UK makes alot of stuff.

http://www.soundservice.co.uk/marine...reduction.html

http://www.soundservice.co.uk/soundproofing_walls.html

http://www.soundservice.co.uk/soundabsorber_walls.html

[Oldad]

Thanks Wiz but that ain't gonna happen. Hoping somebody can do better
Oldad

[Oldad]

The material that builders use between wall sounds interesting. My motor is a 4 stroke but the well acts like a megaphone and amplifies the sound. The well is plywood sheathed in glass so it is the worst possible I guess, maybe aluminum would be worse,a nice cedar box would be better. I wonder where I could find the closed cell foam with a rubber membrane you mentioned? Hmm, wool, now that is thinking outside the box.
Oldad.

[keyhavenpotterer]

Its this stuff

http://www.soundservice.co.uk/therma...nsulation.html

Its what all the eco types insulate their houses with and makes it really quiet.

This is the stuff with a rubber membrane that enhances sound insulation laminated inbetween both halves.

http://www.soundservice.co.uk/soundb...uilt-plus.html

Acoustic mineral wool. very dense.

http://www.soundservice.co.uk/acoust..._wool_AMW.html

You kind of need to do 3 things in 3 layers

1. Anti resonance dynamat or flash band on the panels (lead glued on stops it vibrating/ resonating). Its what they stick onto car panels. Only about 1/4 on the panel needs to be covered and stuck in the centre.

2. Sound blocking (lead or rubber or dense wood)

3. Sound absorption (closed cell foam, carpet)

And have no sound leaks, except it will need its air source.

I used dynamat on my panels, then alot of recyled plastic bottle insulation but compressed it quite hard into gaps to increase its density, then covered it with thin plywood with carpet facing into the van and its made my campervan much quieter. Definately worth the trouble. Only problem is usually these sort of products come in bigish quantities, and you only need a small bit for your engine.

If you want a cheap source of fire resistent sound insulation and don't mind geeing a bit dirty, most cars have a pad of it stuck under the bonnet, under the engine tray or against the bulkhead to absorb sound. You could vist a breakers yard and collect some pads pretty quick, then stuff it in a gap around you r engine? Recycled clothing is turned into sound absorbing felt. Its very dense and used in cars sound insulation. Can be found on Ebay too.


Ed

[Oldad]

Great stuff Ed, my neighbor suggested the car bonnet insulation too. i found some sponge neophrene 1/4 inch thick that might be interesting, not too expensive. Lots of good ideas.
Oldad

[richbeck]

Take a look at this site. If the claims about it are correct it is pretty amazing stuff http://silentcoating.com/
.

[Gib Etheridge]

You say that your well acts as a megaphone. Would it be more accurate to say that it acts as a sounding board? If so you might try cutting away enough of the "transom" to allow space for the clamps so you can clamp the outboard to a second "inner transom" mounted aft of the forward wall of the well on 4 or 6 sound/vibration dampening shock mounts. You would have to add a little cover spaced out a little ways on the front of the well to stop water from coming over the front of the box in way of the cutaway. Here are some ideas for shock mounts. I like the second one down on the right.
http://www.google.ca/search?tbm=isch...w=1024&bih=596

[Breakaway]

Some FRB builders ( Sea Ray, Intrepid) now incorporate a material into their laminate schedule that converts sound-vibrations- into heat. ( DOnt ask me how). I handled a sample of the stuff and its got the feel and heft of Kraft paper--very thin; yet its silver. I heard some demos at the Miami Boat show and both audibly and via a sound meter, the boats with the stiff installed were way quieter.

Anecdotally, running large powerboats whose engine hatches are either balsa-cored or foam cored are much quieter than boats with solid FRP hatches with equivalent power. Talking big boats with a pair of big diesels. So Id say that maybe a simple lamination of Divnicell or Balsa on the outsides of your well would serve.

Kevin

[mcdenny]

Lowes sells a product used for roof flashing. It's about 1/8" thick rubbery tarry black stuff with an aluminum foil facing. Looks a lot like dynamat for a small fraction of the price. Foam factory.com sells noise suppression foam pretty reasonably.

[MN Dave]

Lowes sells a product a product used for roof flashing. It's about 1/8" thick rubbery tarry black stuff with an aluminum foil facing. Looks a lot like dynamat for a small fraction of the price. Foam factory.com sells noise suppression foam pretty reasonably.

Some FRB builders ( Sea Ray, Intrepid) now incorporate a material into their laminate schedule that converts sound-vibrations- into heat. ( DOnt ask me how). I handled a sample of the stuff and its got the feel and heft of Kraft paper--very thin; yet its silver. I heard some demos at the Miami Boat show and both audibly and via a sound meter, the boats with the stiff installed were way quieter.
Kevin

The silver side is aluminum foil and the adhesive is an acrylic viscoelastic damping material. Your hard drive probably has a small sheet of it on the outside to damp vibration. The Lowes flashing works very nicely too. I have an aluminum rain gutter outside my bedroom window that is now lined with the flashing stuff. It used to be really loud and now you can't hear the drips.

If I take you literally, (Looking for an "outside the box solution. Any ideas?) the damping tape can be applied to the outside of the box and painted if you are not fond of the old foil look. Inside the box, there is nothing like a layer of lead in the foam to kill noise, and a bit of the environment.

Gib has a good point about isolating the motor from the box. Structure born vibration is the hardest to get rid of. I like the wool felt idea too, since the open air spaces are effective as long as it is water repellant enough. Closed cell foam is not as effective as open cell for absorbing sound, except that in a motor well open cell foam is only good until you launch the boat, so closed cell is the best for this application.

[Lew Barrett]

Some FRB builders ( Sea Ray, Intrepid) now incorporate a material into their laminate schedule that converts sound-vibrations- into heat. ( DOnt ask me how).

When sound is "absorbed" the result is always heat, that is the physics of it. It's a transducer in reverse. Think of it this way: if you stopped a speaker cone to which you were passing an audio signal, the voice coil would very rapidly heat up as the energy being applied, being unable to move the cone or diaphragm, would have to be dissipated somehow. Essentially, when you block/interfere with the transmission of the "vibrations" what's created is heat.
Measuring the temperature rise is the problem, as the transfer (in most cases) is quite small.

Knowing that, you can see that whatever material does the best job of converting sound waves (energy) into heat is going to do the best job absorbing energy. One key element that has not been discussed so far (Keyhaven Potter does touch on this though) is the importance of making sure there are no leaks outside the box. Sound is somewhat like water; if there is a path, it will find the way.

"Rockwool" is the usual insulation in commercial structures (I can't remember who asked about that). For this job probably the most effective material from the point of view of cost and efficiency will be a dual or triple layer product with a barium (or similar...Ed mentioned lead, but barium is the more frequently used material) membrane/layer, I have used Dynamat (a trade name) and it is quite effective but better in automotive applications where weight and space are key considerations. It works well when wrapped around ducting in structures. Ducts are always a big problem in noise isolation; they are transmission paths.

Another trick/element of noise reduction is lowering/altering the resonant frequency of the boundary layer....another reason why, as a rule, mass matters. Gaining what sounds like a small number....say six or nine dB of isolation can be quite tricky. One important element of how noise/sound affects us is in respct to the spectrum we hear. As anybody can tell you, low frequency material is the hardest to mitigate against. But often enough, killing noise in the mid-band does the trick, which is good because that's where most of the effect will be in the techniques under discussion here. Controlling LF transmission is hard, costly and weighty.

Anyway, I'd pay attention to making sure the box wasn't talking to the outside and use the multi-layer material approach.

Ed pretty much nails it in my opinion.

[Ron Williamson]

I saw this at the boat show;
http://ftna.ca/index.html
The aluminum foam,not the marble.
It seemed pretty interesting,but it was $120 for a 2'x4' panel.
R

[Oldad]

Take a look at this site. If the claims about it are correct it is pretty amazing stuff http://silentcoating.com/
.

Rich, I went to that site and watched the video, amazing stuff if it really works. Two coats of the paint, what could be simpler? Pricy at $150 per gallon, but if it does the job it would be great.
Oldad

[richbeck]

Oldad, I am using it on my build. I researched it as much as possible and by all accounts it works as advertised. I figure if it dosen,t work as well as advertised then I am only out the money and some labor. I can still use sound deadening panels etc. I bought mine at Fisheries for considerably less than 150 per gallon . It is easy to apply and is easily paintable. It will be a while before I will know if it actually works http://northseabuilder.blogspot.com/

Richard

[Mrleft8]

http://silentcoating.com/
Full disclosure: I know the guy who makes this stuff.
It works very well, and the other plus is.... The guy's a sailor. This is the same guy that Jim Ledger got his G-10 centerboard material from BTW.

[Oldad]

Richard, I am not familiar with Fisheries. Is it a chain? Are there any on the east coast? Just went to Google and found them,http://www.fisheriessupply.com/produ...silent+running Thanks to all for the help, I am going with the Silent Running especially since it is paintable and will get in all the nooks an crannies of my motor well without a lot of cutting and fitting and best of all it seems like it might just do the job.
Oldad

[Tom Lathrop]

Some good analysis and advice already offered.

I used the foam/lead/foam solution on the motor box of my boat and it work pretty well, mainly near the motor in the cockpit. Its costly, bulky and ugly. Further forward in the pilothouse steering station, noise is mainly transmited through the hull structure and is just as loud as talking across the motor box. In the 12 years since I built this boat, there have been some advances in sound isolation. Now, I would paint the hull panels near teh motor and not visible with "Silentcoating" to reduce noise transmission along the hull. $150 sounds very reasonable if it can deliver good results. If I remember correctly, the human ear can detect a change in sound level of about 3db which is a change in power of twice or half, depending on whether its less or more. 6 to 9 db reduction would be very nice.

Edited: Just watched the Silentcoating video and am very disappointed in the demo. Notice that the cavity in the control box is a bare metal shell. Then note that the cavity surfaces in the box coated with Silentcoatingis made very thick with something. This will certainly reduce vibrations and sound level, if only from the mass of the thick material. It is not clear what is going on here but it is not a clear demo of the effectiveness of the material as claimed. I'd still like to try some of this material but the results are muddled.

Can anyone help with an explanation of what they are doing?

[BriMac]

Thinking outside the box, I'm in the process of re-engining my old tow vehicle (an old ford van) and I've discovered that the new engine mounts are far far FAR better at reducing the vibration and hence noise generated inside the engine compartment. How about installing your engine bracket on one or more of these modern engine mounts?

[Tom Lathrop]

Thinking outside the box, I'm in the process of re-engining my old tow vehicle (an old ford van) and I've discovered that the new engine mounts are far far FAR better at reducing the vibration and hence noise generated inside the engine compartment. How about installing your engine bracket on one or more of these modern engine mounts?

This is the best way to reduce noise, but......Very few of these mounts are engineered for axial loads and those that are don't seem able to take the mass of typical outboards. It would take a new method of mounting to convert the horizontal loading to vertical loading and take advantage of typical engine mounts.

[Mrleft8]

Edited: Just watched the Silentcoating video and am very disappointed in the demo. Notice that the cavity in the control box is a bare metal shell. Then note that the cavity surfaces in the box coated with Silentcoatingis made very thick with something. This will certainly reduce vibrations and sound level, if only from the mass of the thick material. It is not clear what is going on here but it is not a clear demo of the effectiveness of the material as claimed. I'd still like to try some of this material but the results are muddled.

Can anyone help with an explanation of what they are doing?

Unless you're seeing a different video than I am, I think that you're mistaken about the "Made thick" part.... That's just the paint you're seeing.
I've seen the two boxes in real life, and they're the same construction.

[Duncan S]

You probably have this in mind but would first off look for and spend the money on the quietest outboard you can find. Cheep 2 strokes can be very loud

[Oldad]

I have a 4 stroke and the shape of the motor well is like a megaphone, that is, very narrow down near the prop (just enough for the shaft to turn) and widens out up by the motor (just enough for the motor to turn) creating a funnel that channels all of the noise upward. The 3/8 ply sides of the well are glassed so there is little to absorb the sound. It is a little better with the motorwell cover in place but not much. I was startled at first by the noise and then realized the motor well itself creates the problem. Hoping for the best withSilent Running and really appreciate all of the help. It will be weeks before I know the results but I surely will post when I do.
Oldad

[mcdenny]

I read on another forum about mounting the motor on a approx 1/4" thich rubber pad. I believe these are available for O/B mounting commercially. The guy posting bought a truck mud flap and cut it to the correct dimensions. He reported it making a noticible noise reduction.

[Lew Barrett]

Some good analysis and advice already offered.



Can anyone help with an explanation of what they are doing?

From what I can see, which is limited, they are lowering the resonant frequency of the surrounding structure's panels by painting on a heavy damping material. The fact that they use a thin metal structure suggests that much of the noise (vibration) they are dealing with is the result of sympathetic resonances ( imbalances?) in the fan motor structure which is causing the thin, un-reinforced metal structure to vibrate in sympathy. I too find the video somewhat uni-dimensional and unenlightening on it's own. Some of the explanations in the cover literature is also simplified to the point of uselessness, and uses terms that would not satisfy an acoustical engineer. I didn't dig deeper into the website (time constrain) but the cover page offers little (actually, none I could find) by way of useful specs.

My comments are not meant to be a wholesale discount of the product, but there is no science evident in the demonstration, and I would agree that it raises some questions of authenticity. I suppose we will find our answer after the product is used and reported on here.

Vibration is the enemy; mitigating it at the source is the most effective method. The usual rule is that there is no real substitute for mass coupled with (or, decoupled....that's a pun) isolation, including the creation of multiple barriers and floating whatever structure can be managed. Usually, effective noise and vibration isolation comes about from the use of a number of known techniques employed in tandem.
I too remain interested/curious but mildly skeptical of the efficacy of any substance that can be put on with a paint brush versus the usual run of techniques required to achieve meaningful isolation, but being hopeful and open, one must admit there's always room for innovation. The truth eventually outs!

I found this quote typical:

The old way of removing unwanted noise was to add heavy asphalt mats to the body metal. Believe it or not, this is still done today. What these heavy mats do is add mass to the body panel, often as much as the panel itself. This doesn't remove the vibration; it just lowers the intensity.

I could pick this apart ten ways, but without further explanation from the company, I might be guessing on three of them, but just to start: when was the last time you saw a late model car supplied with asphalt coating?

[Welding Rod]

Earplugs are the cheapest solution.

[Mrleft8]

Earplugs are the cheapest solution.

If you have to buy ear plugs for everyone in a 1 mile radius of your boat, it becomes a little more expensive....

[Gib Etheridge]

I expect that the best that can be done is to seperate the outboard from the hull with the vibration deadening shock mounts and paint the inside and outside of the well with the "silent coating". Some dead air space in the cover, much like a thermal break, would be a big help too.

As an interesting aside, I understand that modern submarines are coated with a rubber membrane which serves to deaden the boats own generated noise as well as absorb rather than reflect active sonar from other sources. Just about everything that makes noise in a submarine is mounted on vibration deadening shock absorbers, even the crew. We were encouraged to wear rubber soled running shoes. I'd sure like to check out a state of the art fast attack, they must have come a long way since the '60s.

[Tom Lathrop]

After viewing the video a couple more times with my old eyes, I don't think there are any thick panels added to the chamber. Fooled by light reflecton and poor quality video. Anyway, I really hope that "Silentcoating" delivers what they claim since it could be a real breakthrough for boats. Hope we get some feedback soon.

[Oldad]

I just ordered a gallon of SR1000 Silent Running from Defender, great price at $109 plus $10 shipping. Hoping for the best but still probably a week or two away from results.
Ol

[Lew Barrett]

In the name of science, it would be very informative if you had a way of measuring the before and after results. You can do this using an app for your smart phone, or by buying a dedicated meter like this one.

Then you (and we) will know with certainty how effective your approach was. In the course of the project, it would be a small but useful investment, and is the only real way to know just what you accomplished.

[Oldad]

I do not have one of those exotic electronic devices but my neighbor does and I emailed him the link to the app. Purely in the interest of science. I will know if it is quieter with it, but it will not be measurable with out some kind of device, I agree. According to the instructions it takes about a week for the stuff to fully cure and should be applied at 60 degrees or better. Since it is snowing here today in Vermont I will not plan on doing it soon although Defender promised it for monday.
Ol

[Oldad]

Happy to report that neighbor just emailed and said the 99 cent dB app is installed on his i thingy. Now all we need is the magic paint and a week or so of good weather.
Oldad

[Lew Barrett]

Don' forget the "before" measurements! Otherwise, we've got bupkis to compare with. I probably shouldn't have said that, but.........:-o

[Howard Sharp]

Yes the engine noise is amplified inside the well, and closed cell foam will help that, but it's getting out through the gaps. I think the single most effective thing you can do is to make sure the seal between the motorwell cover and the well is completely airtight with some kind of soft rubber weatherstripping - automotive stores stores sell it, or McMasterCarr sells a top bulb edge grip seal. The engine is getting air through the cutout in the transom. And a piece cut out of a simple rubber car floormat can be used to mount the motor on - helps to cut some of the vibration transmission. And if you can buy a Yamaha most of the work is already done for you. The cost of all this stuff mounts up.

[Phil Westendorf]

Rubber backed carpet glued to the inside of the compartment. Cheap and easily gotten!

phil w

[Oldad]

Yes, there will be before and after measurements. Weather stripping will be next if the paint does not mitigate the noise sufficiently. Yes, it is a Yamaha 4 stroke but the space it is in has become an echo chamber. The space in the motor well is tight. The motor just touches on each side when full turn. I considered the carpet bit but rejected it when I imagined what it would look and smell like after a season at the dock not to mention cutting and fitting bits here and there in the oddly shaped compartment. If the paint works it will be a blessing. My neighbor got the improved app for the dB meter, cost 1.99 rather than .99. What a bargain. When he opens the app, there is a virtual meter fully adjustable for range and extremely sensitive so we should get good results. The paint came yesterday but I still need to get a few things out of the way before I can do a "before". Hard to wait as I am very curious.
Oldad

[Lew Barrett]

Use the "A" weighting scale, which is intended to approximate the way humans hear.
The flat scale (Z or zero) is actually more accurate and those measurements could be annotated alongside the A weighted ones. A weighting is not for ultra high level noise, is intended for environmental measurements. If your motor is super noisy, it will not be as accurate at the high end of the readings.

But it'll do!

[Oldad]

Here are some reviews. After reading them I am convinced that the product works best in metal structures but I am going to give it a try. It will work to some degree I am sure.
http://www.fishtheclassic.net/forums...p/t-18276.html

[Oldad]

Quick question, can anyone see any reason why I could not paint the inside of my cowl with Silent Running? It supposedly dries to a hard finish, not affected by oil or gas and is fire proof. I may be able to give it the unpainted test as early as friday.
Oldad

[Ron Williamson]

I thought that was your intention in the first place.
R

[Lew Barrett]

The reviews you linked to were not shining endorsements. A couple of guys on that forum expressed the same reservations I have. However, as Ron has said, haven't you decided to go forward in the name of science?

[Oldad]

Oh yes, I am going to do it alright. I did not plan to do the inside of the cowling, just the inside of the motorwell. Someone suggested painting the inside of the cowl and that sounded like it might help, however, I might be wrong, could it hurt to paint it there as well?

[Breakaway]

I'd do it in stages. Paint the well, see how she goes. If you get good results, decide from there whether more attenuation is needed.

kevin

[Ron Williamson]

The engine cowl.
I get it now.
I thought you meant the cowl over the well.
Sure,why not?
In stages,for science.
R

[Mrleft8]

It may void any warranty on the engine if you paint the inside of the cowl.

[Oldad]

In stages it will be, good advice. One of the examples of how it works was on a video from Jamestown Distributors showing a steel plate that sounded like a bell when struck but made only a dull thud after painted and that is what prompted the idea of painting the cowling. I figured why not stop the noise right at its source. I wish I could proceed at a quicker pace but the weather and temp here in Vermont is not cooperating. For science!

[eastern270]

http://nida-core.com/english/
http://nida-core.com/pdfs/pds/nidaco...-H11PP-8HP.pdf
I have used Nida-Core before to make light weight door panels and cabinets in some previous boats. I was told that it's excellent for engine covers because of its light weight and ability to deaden sound. Maybe you can find more info on the link I supplied. Good luck.

[Lew Barrett]

The engine cowl.
I get it now.

I had the same confusion even though I've been following this thread from the start. Nobody's fault but my own. I'm still a skeptic about this material as an ultimate abatement solution in the same sense that multi-layer acoustic materials are, but from the beginning I suggested that this stuff might have it's best application in damping the vibes of sheet metal. Nothing revolutionary there; a heavy coating of flocking or (heaven forbid....it used to be made from asbestos!!) spray on acoustic damping material ("cottage cheese") would do the same thing....alter or lower the resonant frequency of the panel and provide a bit of absorption.