Sound Proofing

[jonathan 4]

I want to re sound proofing a few things, anyone got a good source of sound proofing engine bay safe materials?

 

[Island Time 1,235]

Last time I did it I bought it from Forman Insulation - that was in Wellington, but they have branches all over...

[FlyingBiscuit 0]

I used this stuff: http://www.acoustica.com.au/vybar.html

 

It came from SoPac marine in Albany. 

 

I liked it because apart from being much lighter (the 48F type) it claims to not absorb moisture or disintegrate into millions of little bits like the stuff I was replacing. 

Their little test / demo sound box thing is pretty impressive too. 

 

I found them very helpful, however I was a little to enthusiastic and brought two sheets when I only needed one. 

I will create a classified for the other unused sheet in case it is of use.

[wheels 543]

I have not come across the Acoustica product, so can't comment. But being a Sound

engineer in a past life, I can say that there figure of upto a 30dB reduction is very

impressive. However, it is also slightly misleading, because certain information is not

given, that makes the figure more accurate and informative. Still, it's a good figure and should not be ruled out.

I have used the stuff that Burnsco's sell. It is cheap, easy to install and pretty much useless.

I have also used to a great extent, the stuff Forman insulation sell and it is amazing stuff.

It has a Barium Oxide layer that is dense like Lead and is set between two layers of Acoustic Foam.

It absorbs Sound energy and the Foam acts as mechanical isolation. It is heavy stuff though.

So if weight is of concern, the Acoustica could be worth a look. It is also very expensive and I

got the best deal directly from Forman Insulation.

[jonathan 4]

Weight is not an issue at all, I am after thick insulation (current is about 30mm... but if its good stuff thinner would do, the unit I am doing first is a 5kw genset and I will be measuring it up this week but think its going to be about 5sq m all up....after a good source of general purpose engine mounts as well.

 

I don't expect it to be cheap....  I have used forman for homebrew mashtun insulation may go see them as often better deal direct

[marinheiro 352]

I have just installed some Vybar and certainly pleased with the results - it was recommended by a launch builder who needs to silence very large engines.

Apart from its acoustic performance it does not fall apart after a few years, which the Forman and Pyrotek products tend to do.

It is about 30% more expensive.

[jonathan 4]

you guys just keep raising the $$ bar  

 

will research i am willing to pay for quiet of genset....the main engine doesnt worry me so much

 

how muck is Vybar  per sq m ?

[tuffyluffy 76]

We used the stuff that the car restorers/petrol-heads use for under car bonnets and firewalls etc, its about 1/10 the price of the 'marine' equivalent.

 

I cant remember where we got it but Repco/Supercheap would point you in the right direction. 

 

Its a black foam matt about an inch thick

[Bad Kitty 252]

The Vybar stuff is great, talk to Technical Equipment in Glenfield. The Foreman stuff is rubbish, just ripped a whole lot out that after 9 years is falling to bits & dropping the lead stuff everywhere. 

[Fish 0]

I recently got a job lot of sorber-barrier (foam with a sound barrier and de-coupling layer) and a roll of wavebar directly from Pyrotek. Haven't finished installing it yet so can't say how effective it is. Forman Insulation are Pyrotek's retailer.

 

Also got topshelf cushy float engine mounts from Hancook industries. They were good to deal with, the guy there used to have a Supertanker 34

http://www.hancock.net.nz/

[jonathan 4]

This is a good looking product and the Aussie military use for genset noise reduction.

 

http://www.megasorber.com/soundproofing-solutions/marine.html

 

i think maybe Nexus foams are the nz agent

[Guest 000]

I've tried a few products over the years without too much success. I think the products I tried were OK but the difficulty, for a propulsive engine anyway, is to get a complete insulation seal. Any gaps and the noise will just come right out. I don't know then how you envelop the engine in sound insulation but still provide adequate air flow for the engine to run on and for heat dissipation.

We have solved the engine noise issue by becoming better sailors with a good light weather sail wardrobe - don't motor much at all anymore, and also becoming older and deafer has helped a lot!

[Black Panther 1,584]

I wondered about the air thing as well, don't diesels suck a bit of air and need ventilation? Any of the gurus out there?

[Fish 0]

I wondered about the air thing as well, don't diesels suck a bit of air and need ventilation? Any of the gurus out there?

I'm fitting a blower fan and ducting via a baffle box. Fairly easy to determine the air consumption requirement of the engine, either from first principles, or google search, then basically double it for cooling and ventilation requirements. My 37 hp Izuzu 3 cylinder requires about 30 l/s. The cheapest Burnsco blower, 3 inch, wont do less than about 100 l/s, so its an easy set up.

 

I'm using the wavebar, which is a heavy metal impregnated vinyl, to seal up all of the little gaps and corners in the engine box. its 4 mm thick, so good for making gaskets and flange type thingies for pipes and protrusions into the engine box.

We are then using the sorber barrier, which is he 32 mm thick foam, to adsorb the sound. This stops it reflecting and rattling around until it comes out and sounds noisy.

 

The logic is the engine box should be water tight, one leak, and water will leak out, same with sound energy, hence we are using the heavy vinyl to seal everything.

 

Baffle boxes are also easy to make, given the air flow, max desired velocity, this gives the cross sectional area, and away you go with some nice ply and the adsorber foam.

[Fish 0]

The biggest single improvement we made to engine noise was fitting a silencer on the air intake (air filter).

This removed the deep boom boom caused by the pistons drawing air in. This is the deep low frequency noise that really sounds like a bad hangover headache. Being low frequency, all of the soundproofing materials are least effective at this frequency.

 

Now I can hear all of the other noises like noisy tappets and piston slap etc etc, but the sound proofing will take care of that...

 

I got the silencer from the Beta Engine suppliers, the Engine Room. They were good, and sponsor the Weiti Boating Club, so good to support them back.

http://theengineroom.co.nz/

[wheels 543]

Yes the air intake can be very noisy. But it is important to make sure you get the correct design of intake. Things like length and diameter of intake can end up only "tuning" the intake and make it a specific "note" or even louder. A proper baffle can make a major difference.

When it comes to insulation of sound, it is important to understand several key points.
You have two means of sound travel. Mechanical and Air pressure. They are two very different animals and need to be treated in two very different ways of course.
When it come to sound through Air, it is important to understand that Sound is pressure. Any hole will allow sound out of it. But it can also be a little complex than that, because Holes can sometimes allow only certain frequencies to get through. Mechanical can be a right pain, because a sound can transmit along a pathway for some distance and then a panel can radiate it out into an area some distance away from the engine.

When it comes to frequencies that products will attenuate, many products are specific to the engine type or where the product is intended to be used. A Diesel engine produces a very different Sound that a Petrol does. Some materials are designed to be more frequency specific and thus you need to ensure you are using the right product in the right way.

Fish, the noise you are now likely hearing will Diesel injector pump, if you have an inline unit. Rotary pumps are not as noisy. The inline units are the single most noisiest component, making that loud clattering sound that everyone thinks is the engine itself. Diesel being a slow burning fuel actually is a very quite form of combustion. Another clattery sound can come from bad injectors. If they are old and the spray pattern is more a squirt pattern and the direction of the squirt can lead to a dose of fuel being sprayed onto a very hot component in the cylinder, such as the exhaust valve. When this happens, the cylinder does not fire correctly and allow the fuel to burn in a controlled manner and can cause detonation.

When it comes to Air and a Diesel, yes they need plenty of cool air. A Hot engine room/compartment can rob your engine of a lot of Hp. The hotter the air, the less dense it is and the less gets sucked into the cylinder. This results in loss of power and possible black smoke. One of the biggest tell tale signs of not enough air, is to look at carpet if you have it, over the engine compartment. Anywhere there is a slight gap such as a hatch cover etc, where air can slowly suck through, will leave a slight line of black soot on the carpet. Of course tends to be easy on a launch to spot if engine is under floor. But it simply means the engine compartment has a vacuum because the intake vent is not able to supply enough free air. Blowing air into a compartment is a great idea, but sadly those inline fans can be noisy suckers.

[Fish 0]

Thanks Wheels,

Our injector pump is a Bosch unit circa 30 years old (as is the engine), and I would assume inline due to its shape.

The injectors and tappets are on the list to do, but a wee way down the list after more pressing priorities. I'm hoping the injectors will be the final nice little refinement at the end of the project.

 

So far we have dealt with vibration be replacing very old engine mounts and the drive damper plate. That deals with the torsional vibration from the engine / prop shaft. While we were doing that we also identified a broken engine bracket, which clearly would not have helped the vibration. Next on the list is replacing the Cutless bearing, and then re-confirming alignment of everything.

 

Then we will complete the sound insulation and ventilation of the engine box. Hoping by the time I finish this, our 30 yr old 3 cylinder Izuzu will be so quiet I won't be able to tell if it's running accept by looking at the rev counter

[rigger 47]

Gotta say resiliently mounting the generator would be worth doing if not already done.

[wheels 543]

Gotta say resiliently mounting the generator would be worth doing if not already done.

 

Agreed. In fact, there is a difference in the design of engine mounts that cause there to be two types. Marine and lets just call them Land based. Marine mounts are captive, in that the boat could suffer a total roll over and the mount will not pull apart. Which can be a tad useful. I could imagine there being nothing more Day making than to be at the top of a Roll and having the engine or genset and batteries for that matter, let go and then fall the distance to the coach roof, now floor and most likely carry on through. The newly acquired hole fails miserably at letting the water out.