In need of insulation advice!

Hi guys, I know this has been done before, I've been scouring the forums for a simple answer but somehow it has escaped me. Im building a small project studio in a double brick garage. Just isolating a corner of it, mainly for vocals but it's big enough to get a small band in. I just wanted to confirm the insulation that I needed in my stud walls. I'm hanging 4 broadband absobers from the ceiling, and I believe I've found the correct insulation to pack these with. A place called eureka insulation were offering me sonobatt 48kg density 50mm deep for $19 per square metre. This is fine for my bass traps and absorbers right? But for my in wall insulation, do I use the same? Or double it up to make it 100mm? It doesn't need to be perfect, it's more just to block out external noise, of which there is quite a bit. Sorry guys I'm very new to this and struggling through the un-ending pile of Internet genius' without much avail. Thanks very much, Jack.

Hi, Jack. First, please check the forum rules for posting. Second, your post isn't very clear about what you are trying to do: isolate or treat? Two different things. First you say that you are "Just isolating a corner of it," then "I just wanted to confirm the insulation that I needed in my stud walls". Sounds good so far: if you are isolating, you will indeed need to put insulation in the cavity between the two leaves. But then you confused me with this: "I'm hanging 4 broadband absobers from the ceiling,", well, that would be TREATMENT, not ISOALTION. Broadband absorbers will not help at all to isolate your room. They will help to treat it, yes, but not isolate.

A place called eureka insulation were offering me sonobatt 48kg density 50mm deep for $19 per square metre. This is fine for my bass traps and absorbers right?

You don't say what TYPE of insulation this is: mineral wool, fiberglass, or something else? If it is mineral wool then that's fine for wall cavities. If it is fiberglass, the it's a bit too dense: 32 kg/m3 would be more like it. Either way it's a bit dense for bass trapping. Lighter is better for bass, in general. Heavier is better for mids and highs.

But for my in wall insulation, do I use the same? Or double it up to make it 100mm?

So once again we are back to wall cavity insulation, which is for isolation, not treatment! Confusing... So how much room do yo have in your wall cavity, and how well is it decoupled? Theoretically, filling the entire cavity will give you maximum isolation, but you might not be allowed to do that, due to fire codes. You'll have to check your local codes to find out. However, you also should not "stuff" the insulation into the cavity: you lay it in without compressing it. Compress it too much and it will flank.

It doesn't need to be perfect, it's more just to block out external noise, of which there is quite a bit.

The isolation or the clouds or the bass traps???? Now I'm confused again!!!! :| In any event "not perfect, just to block out external noise" isn't a very good way of determining how to isolate your room, and even less of how to treat it! To isolate properly, you need to measure how loud you are, and how quite you need to be. To do that you just use a simple sound level meter, and measure both inside and outside the room when you are making as much noise as possible, then measure again when you are not making any noise at all, at the quietest time of day. The difference between the loudest reading and the quietest reading, is how much isolation you need: Based on that single number, you can then design the type of construction that will give you that level of isolation. when you have done that, then you can design the treatment to fix the problems that the isolation will cause. In other words, this is a process: you cannot just guess! If you guess in ignorance, then your results will be lousy, at best. If you measure and design based on the principles of acoustics, then you stand a much better chance of getting it right!

Sorry guys I'm very new to this and struggling through the un-ending pile of Internet genius' without much avail.

Well, at least you find the right place! You wont get any myths, legends or marketing hype on this forum. You'll just get solid, sound advice (excuse the pun!) based on real principles of acoustics and physics. Some of the smartest folks in the industry post here, and some of them have written books about designing and building studios. So if you stick around here, you'll certainly learn how to do this right. You might not like what you are told, but at least the advice will be solid! Anyway, please check the "Do not post until you read this" sticky, and provide more details about what you are trying to do! - Stuart -

First of all, thankyou so much. This is the greatest reply I've ever seen on a forum. Ok, the clarification. Please excuse me, Im writing this at work so i was a little hurried in the details. The idea is to build a tracking room on the corner of a garage. I have about a foot of concrete on both the ceiling, floor and brick walls of the space, so from those sides I am isolated well. My first priority is to isolate the space, by adequately insulating my two stud walls. The broadband absorbers and traps are just things I'm foreseeing the space will need, because of the nasty reflections of the hard surfaces. I am thinking 50mm thick insulation in my stud walls, with 16mm sheeting on either side. The thing I was trying to clarify was what insulation I need to adequately pack my stud walls with. Hope this makes sense! I'm obviously a little confused myself. The treatment is of course the next step, but the cavity insulation is all I'm trying to determine here. Thanks Stuart. Jack