Noise abatement

[dhmeissner]

Whilst I'm in the engine room updating various other systems and access is optimal at this time it seems to me that adding some additional sound deadening would be wise. What do the skippers here do?

What say you?
Sound Insulation - Vinyl Foam Barrier Composite - Soundtec | Fisheries Supply

 

[O C Diver]

Have added some of that in spots on the refit. That new stuff either has no lead or fragments in the center layer. The old stuff was a sheet of lead with foam on either side. Waiting to see how the new compares to the old.

Ted

 

[Keysdisease]

Some of the best "bang for the buck" in noise reduction is hatch gaskets and engine room penetrations being sealed up. These small details can add up to significant noise. Insulation will reduce noise, more insulation (thicker/heavier) will reduce more.

As to what diver said, mass is what reduces noise. The foam or fiberglass on either side of the mass layer absorb and decouple enhancing the performance of the mass layer. Lead or vinyl, pretty much same same as long as same lb sq ft to lb sq ft. If your insulation isn't heavy, it probably isn't too effective.

There are also some very good products for under flooring, especially carpeting like acoustic carpet underlayments.

 

[Capt.Bill11]

If your boat has engine space access hatches in the salon putting down carpet and padding can make a huge difference in noise levels.

 

[FlyWright]

I'll probably go the carpet underlayment approach, but haven't placed enough priority to it to dedicate my precious boat funds to it. If and when I do, I'll look hard and long at SounDown.

Since I have carpet already and could use more padding, it seems like the simplest and most cost-effective method for establishing an effective passive accoustic barrier between me and engines. Another approach that I'm very interested in is the active noise cancellation (ANC) systems. Last month, the same week I bought Twistedtree's Kahlenberg horns, my wife received her Bose ANC headset...the perfect offset purchase!! She intends to use them on airline flights. I'd like to see one designed for salon use with mics and a black box connected as an input to the stereo. I've got 5 Bose speakers in the cabin and should be able to provide noise cancellation and music, just like the headsets do.

The headset is extremely effective for background noises. I may wear on my next trip to see how it works. Of course, the Admiral will use them during the horn demonstrations, but they're not really designed for that type of noise burst cancellation. I hear they work well for baby noises, though.

 

[dhmeissner]

Thanks for the suggestions. The "holy place" is below the pilothouse with bulkheads between the salon and the aft cabin.

This is the before picture:

I've taken out the 3 4d's and am re-wiring the whole mess. I have new battery boxes and will be installing 4 6v gcb's and a group 31 start. Also adding a magnum charger/inverter. I may replace the old Torrid water heater now also if I can stretch the budget. Cleaning up the bilge and painting, then add the sound insulation.

 

[markpierce]

The floor section above the engine compartment under the pilothouse is thick and there are rubber gaskets at the hatches. It's fairly effective. One hears the engine of course, but one can hold a normal conversation.

 

[Brooksie]

I second what has been said.
Small leaks let out a lot of sound so step one: close all openings around wires, hoses, & so on. Fit good hatch gaskets. Baffle all air intakes.
Lots of good information on SoundDown's site. With diesel, don't bother with anything thinner than 1" and 2" is better. Buying a roll from SoundDown may be better than from marine supply.
You certainly should do areas behind where you removing / refitting it's your best chance to easily get at them.
I have less HP than you but from my bridge, all you can hear is water, just like on a sailboat. In the cabin you can carry on a conversation in a normal voice.

 

[Ski in NC]

I built my boat from scratch, and while getting it running I started doing things to quiet the salon down. Like most here, my motor is right under the deck in the center of the salon.

First thing: Added sound down to underside of deck between deck frames. Result, slight improvement.

Next: Carpet over deck, including big motor hatch, but not over little access hatch. Result, big improvement.

Next: Weather strip on hatch covers. Result, big improvement.

Next: Seal up penetrations from engine room to salon/cabin environment. Results, improvement in stateroom, but no change in salon. Salon has basically no holes between ER and salon by design.

Next: And this is a strange one!!! Engine throttle cable was zip tied to cable saddles screwed to deck frames. Strange noise came through deck. Added rubber bushings to saddles, noise gone. Same noise I hear at the throttle lever. Injection pump has some wicked vibes that run all the way up the cable.

I think the biggest thing is sealing holes between ER and people spaces. Easier on some boats than others. The sound down was expensive and hard to install, and did less than the carpet and weatherstrips.

Some diesels make lots of noise at air intake, that can be handled at the source.

Now if I can get rid of my prop noise over 23kts without buying a $2500 prop.

 

[FlyWright]

While we're on the subject, what's the typical frequency range of a Perkins, Lehman, John Deere, Cat diesel engine at normal cruise power?

 

[AusCan]

Dave,
I'm going through the same process. A few points I've learned.-

A lot of sound can escape through a small hole or crack. Climb in your engine room and close the hatch. Look for daylight coming in. Thats where the noise is coming out.

Aim for making the engine room as airtight as possible with insulation, other than dedicated air intake and outlet points of the required size.

Sound will reverberate off fuel tanks (and hot water tanks) if they are next to the engine. If you are going to replace your h/w tank in may be worth relocating it, or wrapping insulation around it to absorb the sound rather than reflect it.

I agree totally regarding the heavy weight acoustic insulation. A floating heavy mass is required in the centre of the foam insulation. The cheap lightweight stuff is a waste of money.

 

[Ski in NC]

The stuff I used has the mid- lead layer. Still did not do that much.

 

[FlyWright]

What was the density, Ski?

 

[Ski in NC]

I don't know. I've still got some in the shop, I'll look at it.

 

[Datenight]

Dave and Al,

You can't go wrong with SounDown. I don't have numbers for sound reduction but went from almost unberable at the lower station to being able to converse in normal voice.

It was part of a major (which we did almost all ourselves) refit. We removed the sole to the framing and put down Silomar a SounDown product over the framing to isolate it from the sole. Plywood 3/4 thick next then teak and holly plywood. Two inch SounDown with vinyl decoupler went under it all. The company said vinyl or lead no difference.

As has been noted, sealing all holes makes a more of difference than you would think. The Silomar did double duty as hatch gaskets.

Hope this helps,

Rob

p.s. This was on our old boat.

 

[Insequent]

Whilst I'm in the engine room updating various other systems and access is optimal at this time it seems to me that adding some additional sound deadening would be wise. What do the skippers here do?

What say you?
Sound Insulation - Vinyl Foam Barrier Composite - Soundtec | Fisheries Supply

I have this stuff, and am quite happy with it. Mine is attached with screws and fender washers, we did not use the adhesive version. I would happily use it again.