Flanking sound around joist/ceiling

  • Thread starter Thread starter DrFrankencopter
  • Start date Start date
D

DrFrankencopter

New member
Hi Guys,

I'm wondering if anyone here has taken any steps to prevent flanking sound from bringing their wall isolation down. Specifically, I was wondering about the empty space in the joists above the top plate of the wall.

I'm particularly concerned with this, as I live in a townhouse (end unit), and see the area between the joists as the weakest link in the existing wall construction. I realize that with good ceiling construction the sound transmission will be low, but I really want to prevent the sound from flanking over the wall.

Here's my proposed idea. I plan on installing MDF panels in between the joists at the top of the wall. Installation will be a moderate pain, but I'm hoping that it'll be worth it in terms of reducing flanking sound.

So, what do you guys think? Do you have other ideas for reducing flanking sound?

Cheers

Kris
 
I'm not sure what you mean by Flanking sound - you couldn't post a pic???

I'm currently working on a plan to eliminate sound from a basement getting upstairs but with a low ceiling height in the basement 7' 7"

cheers
john
 
John,

My interpretation is..........in normal construction, there are joists (either approx., 4X2 for a ceiling or maybe 8X2 for a floor in 2 storey buildings) that sit on the top plate of the wall structure.
Now we may give the wall itself all the correct treatment, (internal insulation, multiple layers of sheeting, etc), but I think what Dr.Frank is getting at, is that "void" at the top of the wall between the joists which may create a passage for sound passing through the ceiling to travel into the wall cavity and beyond.

I recently came across some info booklets from CSR, dealing with various construction options for creating "quiet areas" in buildings, obviously using their products:) ...........they strongly advocate the use of Resilient Mounts and channel as well as multiple layers of "correct" plasterboard. The basic principles were much the same as I had learnt from your writings, so that much wasn't really new BUT they do have some great illustrations for those of us who look at the pictures before reading the text:D

Regards :cool:
 
Yeah - I thought that's what he had in mind and your solution is the obvious one, so I figured there might be something else he was refering to. :)

cheers
john
 
Flanking and drawing....

I'd love to post a picture....but I can't use those fance drawing tools. I tried smartdraw, but found it frustrating. I'm much better with paper and pencil.

At any rate, by flanking sound I mean that if you imagine two rooms side by side in a basement. A wall between these rooms has a top plate (say a 2X6) that is attached to the bottom of the joists. For convenience, lets say that this top plate runs perpendicular to the joists. Now, once the double drywall ceiling goes up (on resilient channel, or resilient hangars), there exists a path for the sound to travel up, through the double drywall ceiling, and over the top plate of the wall, and down through the ceiling on the other side of the wall.

My plan to address this involves putting up MDF boards in between the joists, above the top plate of the wall. Imagine it as a wall that doesn't just stop at the top plate, but has fingers that extend up between the joists.

The reason for my concern about this mode of sound transfer is that my future studio is located in the basement of a townhouse. The outer surrounding walls are poured concrete, as is the common wall. But this is only in the basement. The first floor and up are wood. The concrete wall has a high STC, but the joists sit on top of it, and there are just cheezy/sloppy drywall bits covering up the area along the common wall, between the joists. I can actually hear my neighbours due to the low STC of this type of construction. The first thing I address during construction will be strengthening this area, but it has made me aware of flanking sound.

Cheers,

Kris
 
I'm with you now - remember the double ceiling in both rooms means a double (detatched) wall to the other room. (Not enough??)

cheers
john
 
You must log in or register to reply here.
Back
Top