Sound deadening material

On one the refits i was involved in, we completely covered the interior of the engine room in lead faced plywood as a means to reduce engine room noise from twin open valve type Deutz diesels. This was very effective, but heavy solution, and 30 years ago.

Any new high tech materials in light foams with as good acoustic performance as lead shielding to be had?

 

Tell more about this lead faced plywood . Thicknesses ?

 

We had our own press for laminating whatever face veneers we wanted when it came to wood species, but that stuff was ordered in special. Basically a half inch 7 ply marine ply with 1/8 th inch lead sheet adhered on the face. I only lifted one sheet solo, once.

 

Some european engine manufacturer or assembler utilize water jacketed engine cover. Use of water on the water sounds resonable.

 

We use the soundown style sheets a fair bit on engine covers and the wall to the cabin. I've never done acoustic surveys but it appears make a difference. Several different companies make various versions of foam/tin/lead rubber. Locally we have a couple different trade names that make different thickness or foam to rubber arraignment. Seems like for our diesels and hydraulics the only way to knock down those low end noise is with density that's often correlated to weigh.

 

Short answer is no, and low weight to high stiffness materials basically do nothing. As both you a montero seem to note, it is high mass with low stiffness that deadens sound, you need something that absorbs the energy in the fluid, not just pass it on.

EDIT: Xpost with comfisherman.

 

I believe Vetus started doing that.

This is an old 3-banger Perkins, as used in tractors. The exhaust note is acceptable, the general noise, not so much.

 

I was thinking possibly along the lines of a clam-shell housing similar to many generator sets. That would use the least amount of material if it has to be heavy, rather than facing two bulkheads and the overhead.

I thought i would ask first before heading down the hole of sales literature, if any brands stand out as effective.

 

Basic Sound Isolation Concepts | Soundproof Methods https://isostore.com/research/basic-sound-isolation-concepts/

 

I remember those Perkins .Long time ago friend of mine swap this engine into old Aro 4x4 .Gaz-like old 4x4 . 60km/h average and tractor sound .
Engine compartment size ? Hull material ?

 

Almost walk around access, chest high compartment under a wheelhouse. Old oak boat. I suggested noise cancelling earphones might be the cheaper option....

 

We did a fast repower on a skiff and straight piped it... with headset for muffling.

Skiffman volunteered his salary to go towards thr biggest muffler and insulation we could swing....

Sometimes it's the totality of the assault to the senses not just the auditory component.


I'd probably start looking at a high density sheet like a killmat or similar. Then maybe one of the soundown type foams on that.

 

We used a Sound Down product on the inside engine covers on our inboard aluminum jets which tend to be noisy pumping out 350 - 450 hp.
I had quite a discussion with one of the engineers at SD and he said that the problem that most boat manufacturers make is that they do not end up sound insulating all of the surfaces and openings. In the case of an inboard you obviously need an intake in which is hard to mitigate the sound. Also below the engine is difficult to insulate so he suggested to form a bulkhead between the stringers ahead of the engine to reduce the noise. We would run a 3/4 inch Pex on the floor at the lowest point through this bulkhead to allow water to drain to the bilge pumps. We built our own mufflers, having tried a few on the market place. Just behind the riser ( I cannot remember the size) say 10 x 10 x 5 inch, with 4 inch inlet and exhaust and stuff them full with stainless mesh. Similar to a stainless pan scouring pad. ( not SOS pads, the larger mesh scouring pads) The air intake got the same treatment.

Evidently even a small opening from the noise source will can nullify much of the improvement. He likened it to being in a room with the door closed with loud music on one side and then cracking it a 1/2 inch open and observing a significant increase in sound.

The Sound Down that we used had mylar on one side, faced the engine, a 1 inch prox foam then a heavy decoupler then another 1 1/2 inch of foam. This was glued to the inside of the engine
cover. It made quite a difference. Especially as aluminum transmits sound easily.

We had considered a brush/roller product as well. I could not find the product on the internet that met coast guard volatility guidelines but it is out there. They had several You Tube
videos that illustrated the sound deadening effectiveness. There are lots of deadening paint on products but not many are marine approved as they will burn if they catch on fire.

 

Noise canceling technology is high-tech, but have no idea of this would be of any help. It seems to help with the engine noise from an airliner, when using headphones but I have no idea if adaptations could be made for diesel motors. Maybe if blasted through open air speakers to the outlying cabins, or within the engine room itself? When partially sealed room insulation is used, does the engine room have to be cooled, seems like a lot of heat might build up even using water cooled engines?

 

Air in and extraction is outside on deck and outside the wheelhouse. I do not expect the engine room ambient temperature to differ much/if any, when lined.
He has been gifted some aluminium faced (heavy foil) foam sheets, and some foam blankets that look like they have some light lead jackets from an old trawler, and he intends to do a temporary install and test, before spending any money on any specialst acoustic foams. Im hoping to get some more info on what he calls these "lagging jackets".