Building cloud: twice as much is twice as good?

AS the title indicates, I'm building a cloud in my tracking room to reduce floor to ceiling flutter. I came to wonder: the standard fiber glass (rockwool) is 45 mm thick here in Denmark. Would putting up two layers of fiber glass make the cloud double as effective or would one layer actually be enough? Two layers would of course be better to some degree, but enough to justify the extra weight, labor and money?

No. Assuming the rockwool is exposed to the sound waves on the room side, then the double thickness will only improve the low frequency absorption (relative to the single thickness). How much depends on frequency. At higher frequencies, the improvement will be negligible.

Ah, yes. That makes sence. Thanks for putting that in perspective!

Lasso wrote:

Would putting up two layers of fiber glass make the cloud double as effective or would one layer actually be enough?

Jeff is correct (as usual), but don't underestimate the value in having a cloud absorb bass frequencies. The more bass absorption you have in a room, the closer you'll get to a flat response. If the cloud is four inches thick and spaced four inches below the ceiling, you'll get much better results overall. --Ethan

Hi Ethan - yes I see - the cloud has been put up and it has helped tremendously as expected, but I might put a second layer of rockwool up later. Still some bass trapping to go and a little very hi freq. flutter left, otherwise happy :D

Much more important than the thickness is the air cavity beneath that cloud. I presume that have left plenty of air space no ?

and a little very hi freq. flutter left

sound from walls ? part of the ceiling that was not cover ? what density did you use on the rockwool ?

@ andrebrito: Yes - I'm aware of that :D I've just finished the studio and the cloud in the tracking room was the first, most crucial part of the acoustic treatment. The room actually sounds quite nice allready w/o bass trapping, but it will be added later on. So will broad band absorbtion on the walls as needed. Thanks for chiming in!