Soundown again

[Mikey]

Just finished talking with Steve Moyer at Soundown and rereading all the Soundown posts. Those of you who responded to posts about Soundown talk about the thickness but not the weight of the stuff. You can get any of the thicknesses in any of the weights if I understand Steve. Weight is critical. So, my question after all of that (I felt like a reporter in the White House prefacing his question, hoping to get on the news as brilliant. See it works) is, which weight are any of you using and what is recommended? I like conversation and hearing that cheesy VHF radio speaker.

[Dug]

Mikey,

I think I have the 1 or 1.5 inch thick. I used the plastic barrier to save weight. It works great.

Dug

[CaptPatrick]

Mikey,

The heavier the material, the thicker the high density layer is. The foam doesn't do the main work of deadening the sound, the HD layer does. The weight per sheet will be dictated by the thickness of the HD layer.

Weight, from the boat's stand point isn't critical. From the standpoint of you lifting the box, well, eat more Wheaties if you want less noise...

Don't forget that just insulating the inide of the boxes themselves only gives you some sound deadening. The best results will come from also doing the forward bulkheads, lower panels, & hull facings. The more space you cover, the more sound deadening you'll realize.

Br,

Patrick

[Mikey]

Dug, What weight did you use?
Patrick, Am figuring the area of the entire box. Steve says under the engines ain't critical and the sides of the hull above the waterline to use acoustical foam not the expensive stuff. Because my Bride has a hearing deficit and loud noises hurt I want to dampen those beasts as best I can.

[JP Dalik]

Mikey
From experience Use the heaviest sound down you can lift. The engine boxes and the wings all the way to the hull should be done. The front bulkhead and the lower side panel are key noise leakers.
After all that use the 1/2" wide by as tall as is required foam camper tape to seal all the air leaks around the box and bulkhead.
Its amazing how much noise can come through a small gap in your sound down.
After all this work it will not be quiet like gas engines, but it will be alot better than no insulation at all. It takes alot of sound down to get rid of the turbo whine and valve rattle in these engines.
Bad news is they are noisey, good news is they should outlive you.

Good Luck

[Brewster Minton]

In barely lift my boxes but their quiet

[In Memory of Vicroy]

I used the 1" with the lead sheet - did the interior of the motor boxes on AJ, not the wings or bulkhead. Made a huge difference, mostly in the turbo whine, cut it all the way out. An added bonus is the heat trnasfer is all but eliminated, no burned butts sitting on the boxes. I don't think Soundown offered the hi density plastic core when I did mine some 15 years ago, but Steve says it works as well and is not as heavy, but I like lead.......adds about 25-30# per box is my guess. Mine got kinda ratty over the years, some of the mechanical glue on fasteners came loose, the edge tape came loose, and Steve sent me all the stuff to get it back like new.....he's a good guy and one of us.

UV

[nic]

Guys,

We used this product and found it to be very good, easy to install and extremely effective compared to the comparable Sound-Down/(type?) products I have seen, ie foam and lead sheeting.

http://www.acoustica.com.au/aquamarine.html

or this one from the same people:

http://www.acoustica.com.au/vybar.html

If you are interested I will track down the U.S. distributor for you.

Nic

[davidms]

Patrick,

Given your comments on insulating the engine compartment and boxes, will all that insulation affect air intake if your intake is in the cockpit?

How much difference would your air intake kits make in reducing noise in the cockpit?

Thanks, David S

[CaptPatrick]

David,

The sound material doesn't inhibit air flow as long as it's not covering a dedicated air source...

Sound transmission follows essentially the same path as air transmission. If air can get in, sound can get out. Any air source that is designed into the cockpit area, including the engine boxes themselves, will be an escape route for noise.

The side air vents give an alternative source of air that allows any noise to be dissipated outboard of the boat rather than introduced directly into the cockpit. So the side air vents don't directly reduce noise, they just re-locate the noise...

Br,

Patrick

[keysdisease]

Hello Gentlemen,

Thanks for all the kind words. I just want to address a few comments but first some 101:

Capt Patrick: The foam doesn't do the main work of deadening the sound, the HD layer does.

The Captain is correct. Almost all sound insulating material used in boats, regardless of the manufacturer, is based on a 3 component composite.

The first layer exposed to the noise is the absorption layer. This is faced with a vapor barrier (usually silver mylar) to protect the foam from absorbing nasty crankcase fumes and things like oil and water. These foams are open cell, they are supposed to absorb. The absorber layer keeps the noise from reverberating off a hard surface and increasing the noise level.

The next layer is the much discussed “barrier layer.” In the past it was almost exclusively lead, today we use “mass loaded vinyl.” This is just what it sounds like, a barrier to stop airborne noise transmission.

The third layer is the “decoupler” layer. This “decouples” noise from being transmitted to the surface it’s mounted on, bulkheads and overheads.


Mikey: which weight are any of you using and what is recommended?

This has more to do with frequency than anything else. A basic rule is that for higher frequencies you need more coverage and less mass. For lower frequencies you need less coverage and more mass.

A basic recommendation would be a 1 lb per sq ft barrier for gas engines and a 2lb per sq ft barrier for diesel because of the difference in frequency.


JP Dalik: It takes alot of sound down to get rid of the turbo whine

Turbo whine is a very high frequency. The above rule applies in that you don’t need mass, you need 100% coverage. High frequency noise will sneak through the tiniest of cracks, but just tape alone (or anything) will stop it.


Mikey: sides of the hull above the waterline to use acoustical foam not the expensive stuff.

This recommendation means is that you don’t need a barrier on hull sides because you don’t care if noise gets outside the boat. What it does is reduce reverberation by absorbing noise and taking away a hard surface from the noise source. Saves money and weight.


Dug: I used the plastic barrier to save weight

We use the mass loaded vinyl barrier in the same weights we used to use lead. A pound per sq ft of vinyl weighs the same as a pound per sq ft of lead. Performance is same same and the vinyl is cheaper, easier to use and not toxic.


Davidms: How much difference would your air intake kits make in reducing noise in the cockpit?

Great question. The answer is a lot. Capt Patrick is correct in that any direct air path into the cockpit will be a direct path for noise. Air intakes in the hull outside the boat will be much quieter than air intakes in the cockpit or especially on the boxes.


Capt Patrick: more Wheaties if you want less noise....

No comment, I just like it. :-D

Steve Moyer
Soundown Ft Lauderdale