John Sayers' Recording Studio Design Forum

Maybe the fuse was tripped............

Rod

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Ignore the man behind the curtain........

Well, almost total
I am very satisfied, now the wife can watch TV whilst I squeeze the life out of my Tele!

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IS IT LOUD ENOUGH YET?

Thanks for the graphic, Rod.

I have just one more question, unrelated to the ceiling of course.

Insulation: I read here often that the optimum density for insulation is about 2.5 - 3 PCF, but elsewhere I've seen a table (created by you, Rod) showing that Rockwool RW3, which has a density of 60 kg^3 (closer to 4 PCF) is good bang for the buck across the largest frequency range.

Can anyone chime in? There are a lot of products being touted around the UK these days - especially by Rockwool, etc. as there has been a lot of changes in the construction industry regarding sound isolation. The manufacturers have seized on this to have a field day advertising this product and that with all kinds of claims of benefit, but usually without any quantitative data to back it up. As such, even builders are a little bedazzled I think...

Anyway, is there any benefit in using one of the denser products being bandied about, or is the 2.5 - 3 guideline the only way to go?

This is what I used;

http://www.greenmakersupply.com/product ... page_id=66

lots cheaper and Green!

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IS IT LOUD ENOUGH YET?

Boom,

actually,

your mixing apples and oranges here - unless I went temporarily crazy at some point in time that table you are referring to was a comparison of products for room treatments.......... not for in wall insulation.

For insulation I recommend the standard fluffy fiberglass (roughly 1.2 pcf) you loose a little bit on the higher frequencies (as far as TL value goes - but you gain in the bottom end - check out IR-761 if you wish to verify this for yourself.

The more dense the insulation product - the lower the TL values will be in the LF range.

Rod

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Ignore the man behind the curtain........

Rod,

You're right, I went back and checked the post you'd made (on another forum) regarding insulation density and you were indeed talking about room treatments. In all the reading I've done on this, I got some wires crossed. Sorry to misquote you.

But I do find it interesting that you're suggesting a density as low as 1.2 PCF versus something like Rockwool between 2.5 - 3 PCF which has been touted elsewhere on this site.

So, the difference is in the low end?!? Oh boy....
I just finished agreeing to a quote from my builder using Rockwool RWA45 (40kg/m^3 or 2.5 PCF) and thought I was doing the right thing. Should I change that? I am trying to isolate drums, so low end is of great concern.

So far the construction is this:

Wall 1) Single layer brick - 2" Air - RwA45 - Wood Studwork - 2 x 15mm (5/8") Plasterboard

Wall 2) 4" Solid Concrete Block - 2" Air - RwA45 - Studs - 2 x 15mm plasterboard

Wall 3) 2 x 15mm plasterboard - Studs - RwA45 - 4" Air - RwA45 - Studs - 2 x 15mm plasterboard

Wall 4) 2 x 15mm plasterboard - Studs - RwA45 - 1" Air - RwA45 - Studs - 2 x 15mm plasterboard

Ceiling - Independent resting on inner stud wall, 2 x 15mm plasterboard and RwA45 - air - pitched roof (felt and tile)

Should I have him downgrade the insulation to something less rigid to help with low end?

Yes, you should - 20 million Canadians can't be wrong

Inside a wall, the main function of insulation (sound-wise) is panel damping and (to a lesser extent) absorption - you do NOT want anything between wall panels that will hard couple them, which higher density tends to do -

In any and all wall testing I've seen, higher density can improve TL at UPPER frequencies but HURTS it at LOWER frequencies - just a personal theory, but I tend to think this may be (in part) because the denser stuff might be causing the wall to act somewhat as a "3-leaf" construct. Warning - this is, at this time, just a "gut feel" on my part, but the FACT is that lower density INSIDE a wall helps low frequency TL.

Since it's MUCH harder to stop lows than highs, it only makes sense to build a wall for best LOW frequency TL - by doing this, you will automatically build enough HIGH frequency TL into the wall.

For acoustic TREATMENT inside a room, it's a whole different animal - and it's hard NOT to get confused at first since BOTH applications use "insulation", and NEITHER application is using the stuff as it was originally intended

HTH... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...

Heh... It's true, we Canucks are seldom wrong, though I sometimes question my relocation to the UK when I'm costing out my project!

Anyway, I changed my post above. The Rockwool product I'm looking at is somewhere in the range of 2.5 PCF (using the 40kg/16 calculation mentioned elsewhere on this board).

Do you suppose that's still too dense?

I hope my builder hasn't ordered the insulation, yet... I don't want him to think I'm messing him about...

you want material in the 1.2 to 1.6 pcf range.

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Ignore the man behind the curtain........

Alright then... So for those of us in the UK, somewhere between 19 and 26kg/m^3. I'll hunt for some specs on products available in the UK and make it so.

Though I'm a little embarrassed to be making this revision after being VERY specific with him about the insulation already, but such is life. Haha... I'm paying him, I guess.

Thanks Rod, and Knightfly, for your input.

This is something I gave alot of thought to. I really liked the benefit of NO weight being added to the deck with an independantly framed ceiling. I also liked the idea of the lack of contact - the reason it's the most effiecient ceiling frame...

To your question of utility line - Yes, you'd have to have a clear path or run an aditional beam across to bridge under utility.

To give an Idea of what I did (right or wrong, it's what I did and I think it worked.. ) -

Cross bracing for the existing deck:


crude drawing, but you get the idea - more space than an X if you're using 2x6 or greater.

Then run the joists to support the ceiling like so:

Those triangle braces are also in the middle of the ceiling joist against the drywall. If you're spanning greater than 10', I'd likely do something a bit more sturdy.

If dealing with wood framing - if you're REALLY close as I was in the difference between the floor joist and ceiling joist (1'' or less), then pick your lumber carefully (no hockey sticks) and put drywall up right after you frame it up. This way the boards won't kick/warp on you. I had to sister one joist up with a 2x4 as the 2x6 length had lifted.

An update: builder and I have chatted and are both looking into insulation options. It was actually quite difficult to find the density information for many of the products as it isn't listed on the UK manufacturers websites, even under the technical specs. A few calls to the manufacturers themselves were met with an immediate reluctance to deal with a non-tradesman. Only after being rerouted through suppliers (who sent me back to the manufacturers) was I able to get to speak to anyone with useful information. Then, they would ask what I was doing and when I told them I was soundproofing, I would then have to go through explaining to them why I wanted lower density materials, because as far as they are concerned, their expensive, high-density acoustic insulations are the only way to go. Even after mentioning the Canadian government report, many thought that I was barking mad to use flimsy fibreglass for acoustic purposes. When I tried to circumvent that conversation with one bloke by telling him my purposes were "thermal" he retorted, "well why would you need to know the density, then?" Around the mulberry bush again....

Anyway, we all knew this before, but it's clear that even the materials suppliers don't have a full understanding (or have a willful blindness and greed) of the principles of sound isolation, in spite of the data (quite convincing to me) available out there. Heck, the builders are in on it, too. I had a guy come out to do a quote and I was very specific with him about using certain materials, like bog standard plasterboard as opposed to "acoustic" boards, etc. He had crazy ideas about how my concrete slab (isolated) was going to create so much flanking noise that I would need to put down rather expensive rubber matting, etc. and seemed genuinely shocked when I said that I didn't think a little rubber matting was going to make a difference at frequency levels low enough to rattle a concrete slab surrounded by tonnes and tonnes of dirt... By the time his (utterly extortionate) quote came back after nearly a month, he had filled it with so many unwanted and unnecessary products/techniques that his price was fully 3x higher than what I'm going to end up spending. And I'm not doing a DIY build but using a reputable qualified builder. I was quite lucky to find a conscientious guy who didn't have a lot of preconceived notions about sound isolation so when I started showing him diagrams and information gleaned from here, Rod's book, etc. he was open and receptive. I said "do this" and he asked "why" and once I explained the reasoning and showed him the research, he said, "okay". A huge contrast to some of the other know-it-all guys I've dealt with through the quote process.

Anyway, I just want to say thanks to all the forum members here, especially the heavyweights like Rod, and Knightfly. But not to forget all the people who have shared hundreds of pages of their designs and experiences. I've gotten more useful information from here than I did from months of hunting the web, talking to builders, suppliers, and manufacturers. This forum is an incredible resource. Cheers!

Construction has begun with the concrete block wall being built where the roll up garage door used to be.

However, a question about drywall has come up. 15mm plasterboard (5/8" for the folks in the colonies..) is not "standard" in the UK and can be quite a bit more expensive. To keep my original quote intact we're considering using a mixture of 12.5mm and 15mm boards. The builder's initial quote mistakenly used 12.5mm/0.5 inch boards because the measurements were lost in translation... And while that's not a conversion mistake on the scale of the Hubble, it is significant on my budget. My initial reaction (besides the fear of reduced LF isolation ) is to concentrate the heavier plasterboard closest to the sound source - i.e. on the inner wall rather than to mix the two thicknesses on each wall.

Can any of the gurus (or anyone else with relevant experience) chime in? Would that be the safest bet?

I'm in luck in the case that it doesn't turn out because I will still have access to the outside of the two plasterboard "outer" walls to add another layer of 12.5mm board if I need to add mass after the fact, when I've got a few more pounds in the bank again.
Any help would be much appreciated.

Great news, for me at least!

Construction is almost done on my drum studio. The two outer plasterboard walls need to be taped, muddied and caulked, insulation installed over the ceiling and the second of two doors hung. There may be some nooks and crannies in the outer garage shell that need to be plugged up as I caught sight of some daylight creeping in at one of the corners earlier today while crawling around in the ceiling joists. I'm definitely getting a lot of isolation loss through the doorway, which will be doubled-up tomorrow, hopefully cutting off a primary sound escape route.

But, here's the good news. In spite of being unfinished, I appear to be getting some good results. My wife kindly stood outside with a sound meter while I whacked a snare drum tonight. The drum was clocked at 116dB inside. She got readings at about 2 feet from the outside wall of 66dB. Closer to my nearest neighbour's house, she registered 56dB. We are about a 1/4 mile from a motorway and have a constant background noise of between 50-54 dB until very late in the evening. In other words, a little more work, and I should be able to blend into the background! She described the sound outside the studio as a quiet radio or footsteps. Now, I understand that's only an (mostly useless, I know) STC of around 50, and I figured I'd be doing better given my construction. However, I may have underestimated the porousness of the clay tiled pitched roof, and my ceiling is currently just 2 layers of 15mm plasterboard on an independent frame resting on my inner walls.


The real test will be my bass drum, but I'm happy with my results so far. I'm not really concerned with STC points, or decibel levels, as much as being able to blend into the noise of the neighbourhood and not be noticed.

Looking forward to being able to practice and teach again!

Boomka77,

As I'm also in the UK I am intersted in what type of insulating material you decided to use eventually to replace the RWA45.
The builder I've been talking to also recommended RWA45 so I need to give him an alternative.
I'm also struggling to find the density of many commercial insulating materials.

I'd appreciate any help you can give here.

Dave