I need a definitive answer on INSULATION... PLEASE HELP!

[mike1512]

Hi all,

I've searched the forum including looking through the reference section and I can't find anything definitive to answer my question (without searching through hundreds of posts).

I'm a drummer building a ‘soundproof’ practice room from scratch, and I'm trying to find out the best type of insulation to use in the walls and ceiling to reduce low frequency transmission.

The confusing part is, some websites claim that I need a denser insulation and others say I need a low density insulation with more air in it.

I'm also confused about R values - I'm not sure if they are different between countries, but I've seen recommendations on ‘acoustic’ insulation with values ranging from 2 to 38 or higher.

If someone can give me a clear explanation of this so I know what to look for… that would be greatly appreciated

Mike

[Gregwor]

Great question. I've been confused on it myself as I've read so many contradicting posts about it. John has stated that more density = lower frequency performance.

70x performance.png

You can see that the lower density insulation (701) performs better at 250Hz but at 125Hz, 703 was the best..

The best I can offer is this info which I've compiled over the years.
(NOTE: I've had John tell me this is wrong)

Fiberglass in kg/m^3
High Freq = around 40 (others say 60-80)
Mid Freq = around 35
Low Freq = 20-25

Mineral Wool in kg/m^3
High Freq = around 65 (others say 90-120)
Mid Freq = around 55
Low Freq = around 30 (others say 40-45)

Now, for in the cavity of your walls, it makes sense to use insulation that perform the best at the resonant frequency of the cavity. So, typically you would want an insulation that performs well at low frequencies. Personally I ended up getting the most dense pink fluffy fiberglass I could get as the others had a density that was too low.

Greg

[DanDan]

My take is that at best the fibre damps the air void, but also damps the actual plasterboard against bending waves, by lightly touching it. So damping of multiple and interacting resonances I reckon.
A dense batt will not do that, unless an absolutely precise fit.
I have some pretty definitive test publication from Isover. I'll post it if I can find it. They found no difference at all over a range of densitie inside the void.
They also found that a full fill was optimum. I recommend buying the for purpose Acoustic Rolls or Partition Rolls and fully filling the void but ensuring real but not squeezed in contact with the boards.

Air borne sound insulation.ppt

[Gregwor]

DanDan,

Great slideshow! For anyone who doesn't want to download and open the slideshow file, here is a picture addressing the initial thread question:

Insulation Density In MSM Cavities.jpg

Greg