The system they have is primarily for sound insulation between domestic dwellings - and I cannot find the specific frequencies where these specs relate to. 60dB is great for speech, but 60dB reduction on a kick drum may not be (edited by Moderator...)
This shows how a good reduction figure drops as the frequency goes down - and also has lots of useful stuff. These system walls are really just removing the timber element - the work being done by the layers on the more mass=more attenuation principal. The domestic standard doesn't seem very detailed - just average sound reduction. Your lack of drums makes it easier. A single layer of brick, a 80mm gap then 18mm of plasterboard and 18mm of MDF with rock wool cavity insulation means that outside, at night when it's quiet, I can just hear the bass drum.

Hmmm...it seems like perhaps these system walls are not the best choice for me then?

From what you are saying, I could get far better attenuation with your brick/rockwool/plasterboard solution, and that the total thickness would be <300mm?

I think the key feature with those is speed of erection. The old fashioned stud work wall is more complicated to build, but if it's DIY, maybe that isn't a real problem, and timber is easier to manage around odd structural features. The essential thing you need is mass. I've done quite a few of these projects in the past 20 years and none have been poor, and in most of them, I also have a layer of insertion board too. The ones here had a design problem - I needed a space between two walls that fitted some equipment, and to get the internal width, I had to reduce the wall thickness. It doesn't seem to have made the isolation worse but there is one thing the loss of the insulation board makes obvious. If you knock on the inside layers, the totally solid sandwich transmits the mechanical noise quite well - i spotted this when building it, compared to the previous one. The layer of insulation board helps with mechanical transmission.

In my earlier studios, the walls were all plasterboard and insulation board layers - but plasterboard isn't good at resisting impacts. Bringing amps and drums through from room to room caused a few 'collisions' and the plasterboard got tatty quickly. Other people don't seem to have this problem - but half of mine were used by students, not the most careful people. I now use plasterboard laid vertically, as normal, but with the MDF horizontally. This gives a join at 4ft, so I then cover this with a timber strip with rounded edges, and then fit an identical one below it - with the gap just big enough for electrical outlets.

If you are building in your basement, and the walls are brick or block then if I wanted the best performance, I'd build a two sided room within a room. On the outside, two layers of PB, then 75mm timber, then a PB layer, an IB layer and then a single layer of MDF. 18mm MDF on the inside is really strong - and has the benefit you can screw to it anywhere. I'd be happy with 12mm sheets for the others - giving you a total wall thickness of 143mm. Gap wise between the wall and the inner just enough to get some insulation in. I've done this with rock wool (expensive) and fibreglass - the modern thicker stiff, just compressed to fit the gap. I don't have test gear sufficiently accurate to determine a performance advantage.If you do this approach keep in mind that an inner room with plasterboard on the outside is difficult to physically do - so I do these ones in panels, on the floor, then erect them, bolts them together and then do the inner skin.

At first I got really hung up on the published specs, striving to get the performance figures the specs indicated, but I soon realised that the real limiting factor is the leaks around doors and windows, roof panels and of course ventilation. One layer less on the walls means the room 'leaks' more, but of course any windows might leak more. I've found the heavier solid fire doors work pretty well. I did discover my rather DIY standard of carpentry meant I did have gaps around doors where my frames were a little out of square. I solved this one by hanging the door to one stud and lining, then adjusting the other linings to be very tight to the door without binding, then install the next stud to that! Perfect door hanging. They get very hot and smelly/stuffy. If you fit ventilation, then you puncture your linings and create opportunity for sound to escape. So can you get by by opening the doors every now and again, or must you have an intake/exhaust? You can make labyrinths out of MDF, line them with insulation, and they work quite well, but simple things like sucking foul air out rather than pushing clean air in make big differences to the noise level inside. 8" duct fans running slowly are quieter than a 4" fan running flat out. The duct fan itself needs isolating from the room or you hear the rumble.

Last thing - don't be tempted by cheap patio style doors - they're good but they often leak. Not the glass - but the frames. UPVC ones are hollow, and the plastic thin - so sound leaks through. Some wooden ones seem to be made out of very light wood - they leak too. The solid mahogany ones are better, but even a triple glazed panel still leaks a little - the glass is too close to it's neighbour, but they are amazing heavy!

That's about as much as I can think of at the moment.

" I'd build a two sided room within a room."

Now right here when you instruct the poster to actually build a 3 leaf assembly do you have any information to help him to understand that this type of wall assembly will result in a decrease in transmission loss at low frequencies?

I am out of town and can not address this issue over a phone typing system....but I will when I get in.

Ramshackle...do not listen to what this person is saying and assume he knows something.

He knows something....he does not know enough to help in this issue and will cause you problems...do not let his long winded ness be confused with authority..it is all hack talk.

Well, all interesting replies. I still haven't got the answer to my original question...what do those numbers mean? Is it good enough for what I want to do, or is there not enough information there? (Or is it plain not good enough?)

I'm looking at these solutions because:
a) they are tried/tested and have published performance numbers...what ever they mean. If I can figure out how that relates to what I want to do, then I'm inclined to trust them more...
b) I know these wall assemblies are used in commercial buildings - cinemas, offices where sound insulation is important, radio stations etc... It's advertised on the british gypsum site. But I've not heard of them being used in recording studios...but I'm not building a 'full blown' recording studio. More a glorified rehearsal space with the capacity to do a bit of recording and mixing. No drums or amps (ever - we go elsewhere when we want amps. We would use some small percussion in this space).
c) The various materials to build these walls is readily obtainable here in the UK (B&Q, TravisPerkins and other places seem to carry most of it, even the more specialist plaster board types (the 'soundbloc' board for example)) and by my calculation would be cheaper than all the wood required for a staggered stud wall...

Reading the replies makes me think that perhaps go right ahead and start a new thread with the floor plan and what I want to do...

I checked the rules and there is nothing there to cover having different opinions, that have worked for me. Inappropriate comment? Wow, that's a stretch of the rules isn't it? Is it so inappropriate to detail techniques that have worked for me, even if they don't follow the acousticians rule book? Sensible discussion on parts of my post would have been helpful to others, but nope - just have a pop and cause me of long windedness? I tried to be helpful, and as detailed as I could to a fellow Brit. If the forum want short sound bite length posts that's a bit sad. Warning me in a message that I may be banned for the post is amazingly over the top as a response.

I didn't realise that one criterion for posting here was absolute adherence to science, and public stoning for diverting from the truth as known to acousticians! There really was no reason to be so rude. You could have contacted me privately to explain, but no let's just say he knows nothing. Nice!

I decided to go into more detail on what I am trying to do rather than just understand the stats for these wall systems. So I have created a new thread about my specific problem:
http://recording.org/index.php?threads/soundproofing-for-rehearsal-space-project-studio.57208/