Multi Leaf Wall Questions

[spencerc]

Hey Everyone,

So I have finished reading:

"Home Recording Studio: Build it Like the Pros"
"Master Handbook of Acoustics"

It clearly states in these books that anything over a two leaf wall system is 'bad'.

Now I am about 1/4 of the way through Phillip Newell's "Recording Studio Design" and he is using multi leaf wall systems all over the place (although not in the typical way the other two books described multi leaf walls).

Can anyone explain the discrepancies between these books?

Thanks!

-Spencer

[jayfrigo]

Originally Posted by spencerc

Hey Everyone,

So I have finished reading:

"Home Recording Studio: Build it Like the Pros"
"Master Handbook of Acoustics"

It clearly states in these books that anything over a two leaf wall system is 'bad'.

Now I am about 1/4 of the way through Phillip Newell's "Recording Studio Design" and he is using multi leaf wall systems all over the place (although not in the typical way the other two books described multi leaf walls).

Can anyone explain the discrepancies between these books?

What kind of specific construction is Newell suggesting, and in what application? Do you have a page reference? More than 2 leafs usually diminishes overall isolation performance, though if you do the calcs and measurements, it may improve in one area, while getting worse in some others. Therefore, on the whole you'd have to conclude that it's worse for generalized situations, but in a specialized application, use may be plausible. Without specific things to compare, I'm just flapping my gums.

[spencerc]

Thanks Jayfrigo!

Pages would be:

Page 7 (diagram which he references a lot)
Page 58 Diagram (although I'm not really sure how many leafs this would be)

And then mostly just Chapter 5 "Designing Neutral Rooms" when he is talking about setting up rooms.

Page 144 at the bottom has another diagram.

Now I think he is mostly using these extra layers as LF absorbers....but like you said, wouldn't that reduce the overall isolation?

I also remember reading somewhere (but I can't find the page number right now) that he is talking about using multiple M-A-M structures in the wall so that they all have different resonant frequencies and that they all should cover up each-other's resonances. If your using more than one M-A-M (or M-S-M if you wish) than that definitely means more than a 2 leaf wall. I'm pretty sure he references the page 7 diagram for this.

Note*** I have the 2nd edition of the book.

Any further explanation would be greatly appreciated

Thanks!

Spencer

[Northward]

There is a BIG difference between 3x the same "leaf" (= not recommended) and a complex wall built of different layers made of different materials.

In studios we design, more often than not walls can reach up to 1.2 meters thickness, and it's not just for the fun of it

[spencerc]

Is there any further/more in depth explanations on this?

[Northward]

There is a lot to play with in complex walls, but one of the obvious techniques is to create variations in structures to avoid common coincidental/resonance freq (heavy variations in mass, resilience, studying the stiffness of the different layers for ex)

You can have 66Hz / 31 Hz / 22 Hz / 76 Hz.

Most big studios which are built as a series of decoupled bunkers typically have at least 4 layers involved: 2x the structural concrete walls of each bunker, and an inner, lighter, structure whose role is double: give the room it's desired shape (RFZ, FTB, cockpit design etc) and enhance soundproofing.