Roofing lead used for soundproofing

I would use sonex.

Jim

It is overkill, but it will work just fine. Usually the soundproofing lead is 1/64 thick and about 1lb. per Sq.Ft.

Owens Corning makes something similar called 703 insulation board. I've used it and it works pretty well.

Steve.

Thank you. When you say overkill, in what sense is it an overkill? In terms of benefit per weight of lead shielding added? Am I not going to get better soundproofing from 2.5 times thicker lead?

I did a quick google search and found many types of sonex. Which one would you use? Do you have experience with it?

thanks

I would sure think the additional mass would help a lot at lower frequencies. Lead is used because it's "dead"; no flexural resonances because it's soft. If your roofing lead is soft (bends easily), it'll be a good sound barrier.

"Ignoramus1606" (clip) Am I not going to get better soundproofing from 2.5 times thicker lead? ^^^^^^^^^^^^^^^ Very likely yes. Much or most of the sound reduction comes from the mass. Your lead, being much thicker, will be much heavier. I don't know the compositions of the two types of lead being compared, but I would guess that soundproofing lead is unalloyed, in order to make it very soft, to maximize damping. Roofing lead could have something added to make it stiffer, or springier, so the damping would be less--which would make it less effective for sound deadening.

There must be a reason you are asking about roofing lead--you've got some to use up, maybe, or it's available as scrap. In that case "overkill" won't cost you anything. You can't really make a genset TOO quiet.

You may want to think about this for a minute. You are looking for transmission loss and vibration damping, properties for which Sonex is not noted. You want to look at how the noise is being coupled to the air. The big problem in this type of system is providing the combustion air while maintaing some acoustical isolation. Some time in the library may save your buying materials (lead, foam, or whatever)that don't do the job you had envisioned. You may want to try integrating the sound isolation properties into the structure instead of tacking up stuff and hoping for the best.

Kevin Gallimore

Don, I will check softness when I buy it at the roofing supply place tomorrow.

No, I will have to pay for it. $3.11 per square foot, I will need about 50.

If only it was about combustion air. This is an air cooled genset that requires a huge quantity of cooling air to cool the cylinder fins.

I have been reading about this stuff, it seems that there is not as much systematic knowledge available.

I've done alot of rebuild and repair of a similar gen set, DOD model MEP-018A which is about 10 KW, air cooled, gas engined. I am not optomistic about your *ever* getting the sound level low enough to be satisfied. Those things are noisy. The maintenance manual shows how to lessen the noise by locating the gen set far away and covering it with sand bags. This is my way of saying you have a real task ahead of you.

Jerry

MEP-018A is not at all the same. I am very familiar with MEP-017a, which I bought from the miitary and resold at a modest profit. With MEP-018A, cooling air exhaust cannot be ducted outside, whereas with my Onan, it can be. So, I made a duct out of some tinned ducting materials. I hope that it holds up.

Yeah, I remember that.

I completely agree. That's why I wonder if lead sheets are going to be a waste of time and effort, given the air requirements.

Oh boy. The usual treatment is a serpentine air path lined with absorbent material. You might try a box made of cement board with a serpentine path (lined with rigid fiberglass insulation) in the front and back for cooling air. I don't believe Sonex, Soundown or lead in an open box is going to buy you much. The fix may end up to be a larger piece of property and heavier electrical cable.

Kevin Gallimore

Thanks Kevin. I have some hopes that what I do will improve situation somewhat. Specifically what is going to be behind the generator is a high and wide deck. So, if I manage to redirect sound towards that, as opposed to towards the front of the genset, my situation will improve.

I feel that some experimenting is educational, although there is some point at which it will become more tiring than educational.

Sonex is basically anechoic foam. We use it because we have many very noisy vacuum pumps that run in our labs, and they would drive us nuts otherwise.

These are hp and up pumps that are electrically driven.

We build a large plywood box around them lined with sonex foam, and install one or two large muffin fans to circulate air through the box so the pumps don't overheat.

Once they're boxed, you can't tell they're running, except for the fan white noise.

Jim

As long as you are already familiar with the noise level and think you will ever be content with the level, I agree that a big, thick lead box is a good way to lower the noise. I dont think you could have choosen a better material.

Jerry

The nice thing about the sonex is it's relatively cheap and the shipping won't kill you. If you buy a few hundred pounds of sheet lead and find that it won't do, then you still have to dispose of it somehow. :(

Plywood box, lined with sonex. Labyrinth to allow cooling air and a big muffin fan, driven electrically.

Jim

Thanks Jerry. I feel that if a plywood box reduced noise by 5dB, then, making same box even more soundproofed and adding baffles can get me somewhere, especially considering the fact that the genset will be outside and I care about some directions of sound propagation more than others.