I question the density of tar paper anyway
Hello Dan. Its not the density, it's the mass. If the tarpaper was as thick as 1/2" drywall, my guess is it STILL wouldn't match the drywalls mass.
What are your thoughts on drywall depth – ½ or 5/8?
The more mass, the better. There are people who are using as much as TWELVE layers(thats on TWO leaves) of drywall, to lower the Transmission Loss frequency to equal that of a concrete floating floor. Use as many layers as you need to meet your transmission loss target. Which is usually the problem, as most Homerecording people's budget are usually much less than it really takes to isolate low frequency. This is the concept. IF you build to isolate low frequency, you've already taken care of High frequency transmission. But determining what it takes to achive Low Frequency Transmission Loss(LFTL) is extremely difficult, not to mention the actual construction. This is why homestudios are usually a LFTL compromise. However, if late night drums, high SPL guitars/bass, and cranky neighbors or household members are not compatible, then you will fail if you don't bite the bullet.
Not only does mass contribute to TL, but the depth of airgap will too. If high SPL is what you are trying to isolate, I would consider DOUBLE WALLS instead of staggered stud, with as much airgap depth as you can afford to loose in the rooms. And then there is the matter of the connections between the wall framing and the existing floor joists above. Direct fastening will negate any isolation attempt at the ceiling. Wall framing needs to be de-coupled by use of "sway" brackets with resiliant material between the bracket and the wall. Here is a design one member here used. See the drawing below. This was a SINGLE wall between studio and sound lock. Double walls or staggered stud would be similar. This one happened to have a beam in line with the wall, so the bracket design was fairly easy and straightforward.
I don’t plan to do this on the walls that face concrete.
What are you planning here? If it were me, I'd attatch 1 1/2" thick furring strips, fill the voids between the strips with rigid insuation and then fasten Resiliant Channel to the furring for decoupling a couple of layers of drywall over it. Not only will this give you better isolation, it will provide insulation as well as built in absorption if the voids between the furring are caulked well. I'd seal this concrete prior to doing anything though.
I’m going to be using Owens Corning #703 in places, and a couple of other products to try to reduce some of the plumbing and duct work noise at the source. Your thoughts here would be greatly appreciated
If you have plumbing exposed in the areas for the studio, personally, I would
frame for enclosing them with drywall. But without seeing what you are up against, it's hard to say. If these are in the floor joist cavity above, see below. As far as HVAC, if the basement SHARES ducting with rooms above, I would plan on changing these. Flanking through these ducts could totally negate any isolation attempt between upper and lower areas. Studio areas should be on their OWN supply and return ducts, with at least one 90 degree bend. However, studio HVAC is a specialty, needing HIGH VOLUME DELIVERY
at LOW VELOCITY, which is opposite of most residential installs. Again though, without knowing the particulars of your existing conditions and planned alterations, not to mention budget and skills, it's hard to say what is
feasable. Compromise is at hand here probably. Especially if the ducts to other rooms above are below the joists. That is another matter to deal with entirely.
Also, the use of rigid fiberglass for isolation is a waste of time. Yes, it will absorb but because of the way resistance absorbers work, it does NOTHING for isolation. Mass and decoupling are your friend. I would suggest if budget is your main concern, save yourself some money by NOT using foam products for treatment. 703 or mineral wool products covered with fabric are your friend in this application. Especially if you have concrete walls in a space. This creates the possibility for specular reflection with no absorption, which translates into MUCHO BASS TRAPPING!! Normal two leaf walls built with drywall provide built in bass trapping to a degree, as they act as membrane absorbers. With concrete, there is virtually no absorption, so extra bass trapping is the only solution, especially in small rooms. I would suggest the use of CORNER SUPERCHUNKS of 703. Do a search here as I have already posted drawings and illustrations of SUPERCHUNKS. These work superb for modal absorption as room modes terminate in corners. ALL of them, even at the wall ceiling/floor intersections, not just wall/wall intersections. Patchwork layouts of 703 panels on the walls and ceiling also provide extra absorption as diffraction around the panel edges and reflective boundarys create an "impedence" difference, which is beyond the scope of this post to explain. Even patchwork use of throwrugs on the floor will contribute to this effect, which gives you a good start at diffusion as well.
I’m using a drop ceiling that supposedly reduces sound by 55%. I’ll be using insulation/acoustic batts between the floor joists to help there as well.
Hmmm, 55% huh? So they say. At what frequency? Usually, these kind of statements are a joke. Yea, maybe 55% at the speech range, but check their spec's at 125 hz. You will see. I've already told you, MASS is your friend. People try to avert this fact by believing their projects are not subject to physics
IF you want to keep sound from transmitting to the upper floors, BITE THE BULLET! DECOUPLED MASS is the ONLY WAY!! Otherwise, suffer the compromise consequence, PERIOD. Hope this doesn't appear as negative. On the contrary, truth is hard to swallow sometimes. But better to be informed PRIOR to a decision, than disappointment in ones power to outwit physics.
fitZ
