952 Studios Construction!

[Soundman2020]

Looks fine to me! Louden's first ratio is a good one. It's also not necessary to hit the numbers spot on. Rather, just get close, as you have.
Some people think they need to tweak the dimensions exactly, down to the nearest millimeter (1/32"), but it that's not needed. Room ratios are all about low frequencies, where the waves are many meters (dozens of feet) long, so tweak things to extremes isn't going to accomplish much. Also, there's no such things as a "perfect" ratio: just good ones and bad ones. The goal is to stay away from the bad ones, get close to one of the good ones, and you are done!
Your ratio is just fine. You are well inside the Bolt area (a useful indicator), your Schroeder frequency is 200 Hz, which isn't great but not much you can do about it (you'd need a huge room to get it down lower!), and your Bonello diagram is smooth (another useful indicator), so I'd say you are good to go!

- Stuart -

[eightamrock]

Source of the post Looks fine to me! Louden's first ratio is a good one. It's also not necessary to hit the numbers spot on. Rather, just get close, as you have.
Some people think they need to tweak the dimensions exactly, down to the nearest millimeter (1/32"), but it that's not needed. Room ratios are all about low frequencies, where the waves are many meters (dozens of feet) long, so tweak things to extremes isn't going to accomplish much. Also, there's no such things as a "perfect" ratio: just good ones and bad ones. The goal is to stay away from the bad ones, get close to one of the good ones, and you are done!
Your ratio is just fine. You are well inside the Bolt area (a useful indicator), your Schroeder frequency is 200 Hz, which isn't great but not much you can do about it (you'd need a huge room to get it down lower!), and your Bonello diagram is smooth (another useful indicator), so I'd say you are good to go!

- Stuart -

Thanks Stuart! I did my best when planning to do all the research but there is a lot to know. Im certainly going to be lightyears ahead of my last boxy studio with a 7ft ceiling and that will be fantastic.

Ill definitely be asking for some treatment advice for those sub 200hz modes when I get to that step. Im not really sure how to apply knowledge of the modes I need to treat with actual treatment...

[eightamrock]

A big fat stack of laminated glass for the exterior windows. 5/8” and 3/8” for each window. I’ll be using Stuart’s built on site method for installation.

[Soundman2020]

Cool! That's a lot of glass! Did you manage to find acoustic laminated, or is that just normal PVB laminate? Either way it looks plenty thick enough to get you substantial isolation.

- Stuart -

[eightamrock]

Ok guys, another quick question specifically on insulation.

I built the exterior walls with 2x6. In each cavity I now have 2 layers of 5/8" drywall (1.25" total) and 3" bats of rockwool safe and sound. This leaves about 1" of space in the 2x6's that is unfilled. I then laid out my inner leaf with 2x4's with a 1" air gap from the outer walls. This gave me 2" of free air between layers of insulation. The inner leaf having 3" bats of rockwool safe and sound as well.

I had thought this was the best way because my total air gap (between layers of rockwool) would be 2". Recently Glenn said I should/could put compressed pink fluffy cavities as well to improve isolation. I can do this, but I did not budget for it so it would be over and above what I am already over and above. Additionally, the only insulation I can find (r13-r19 is faced insulation. So 2 questions:

1. Is the cost/benefit worth it or will the improvements in isolation only be marginal with adding compressed fiberglass in the cavities?
2. If the benefit really is there, does it matter if there is a vapor/paper barrier in the middle of the wall attached to the face of the 2x6 studs? Wouldnt this actually decrease the resonance attenuation because it is a semi stiff surface?

Im really looking for someone to say "just do your 2 layers of rockwool everything is fine" but honestly if there is a huge benefit to be had I might want to make the additional investment in pink fluffy....

Thoughts?

[eightamrock]

Source of the post Cool! That's a lot of glass! Did you manage to find acoustic laminated, or is that just normal PVB laminate? Either way it looks plenty thick enough to get you substantial isolation.

- Stuart -

Just normal PVB! I didnt know there was such a thing as acoustic laminated... but I dont think I could have afforded it anyway. This stack of glass was already close to $5k.

[Soundman2020]

Just normal PVB! I didnt know there was such a thing as acoustic laminated...

There's different types of acoustic laminate, with different properties, but they all do add a bit to the cost! I paid about 12% more for acoustic laminate in some windows and sliders last year (as compared to normal PVB laminate), but there were other options too... with rather higher percentage ratings! So your 5k would have been more like 6k, or 7k, or... probably not justifiable, for the small improvement you might get!

The benefit from acoustic PVB (or other acoustic interlayers), happens around the "coincidence dip", which likely isn't going to be much of an issue for you anyway. Coincidence is kind of hard to describe, but it basically means a reduction in isolation for a small range of frequencies where the wavelength of the sound in the air happens to match the wavelength of a bending wave in the glass, at certain angles of incidence. It's usually in the upper mid frequencies, or the low end of the "highs", depending on the characteristics of the panel (glass, in this case).

I've been meaning to write a bit out this for a while, so I'll just do it here, on your thread, then later post links to it.

This whole "coincidence dip" and "bending wave" things probably doesn't mean much to anyone, so let me explain a bit more:

Low frequencies sounds hitting a wall, ceiling, floor, or window, cause the entire panel to "wobble" in and out (as though you were pressing on the panel with your hand, then releasing it, repeatedly), but higher frequencies cause "ripples" that travel along the surface of the panel, sort of like the ripples you seen in a calm pond or lake, if you drop a stone in. There's another difference here: the speed of sound for normal compression waves (the ones that cause the "wobbling" at low frequency) is constant, regardless of the frequency, but for the "ripples" (bending waves), the speed of sound is different for each frequency. Or said another way: each bending wave-length (=frequency) causes waves that travel at a specific speed, so different frequencies cause "ripples" that travel at different speeds. And as a result, it turns out that, for every single frequency above the point where this effect starts happening, there will be one specific angle of incidence (the angle that the sound wave hits the wall) where one specific bending wave in the wall matches the wavelength of the incoming sound. So the panel will resonate at that frequency, and thus it does not isolate well for that frequency. That "lowest frequency where the effect can occur" happens when the incoming sound wave in the air is grazing along the panel, almost parallel to it (going in the same direction as the panel surface), and then for every angle of incidence above that, resonance will happen at a slightly higher frequency, until you get the highest frequency where the waves are arriving "head on" to the panel (perpendicular to the surface). That region, where the frequencies in air can line up with the various frequencies in the panel, is called the "coincidence dip", and is a somewhat broad region.

For most materials commonly used in building studios, the dip will occur somewhere between maybe 1 kHz to maybe 5 Hz, and will be a few hundred Hz wide. This region is usually well isolated anyway.

If you are interested, the equation for calculating this effect is:

Fc = c² / (1.8 * t * Vl * sin²(a))

where:
c = the speed of sound in air (m/s),
t = the panel thickness (m),
Vl = the longitudinal velocity of sound in the panel (m/s)
a = the angle of incidence.

The "longitudinal velocity" is different for different materials (wood, glass, drywall, etc.): you can find tables on-line that tell you what it is for each type of material.

Coincidence generally isn't too much of an issue for typical home studios if they are designed and built well, but it is something to be aware of of you need high isolation.

One interesting point here: If you make a floor (or wall, or ceiling, or whatever) from several layers of material, and you glue them all together, then that brings the coincidence dip DOWN in frequency, which could indeed create a problem for you (it reduces isolation)! Which is why you should not glue together layers of drywall in your wall! If you just leave the layers on top of each other (such as by using only nails or screws to attach them to the studs), then they are free to "slide" past each other when they vibrate, and that can create frictional losses, which improves isolation at the coincidence dip: the dip doesn't go so deep. If you then also add a resilient damping material in between those layers, then you can improve those losses even more (higher losses = better isolation), and if it happens to be a visco-elastic compound, then you can improve them more still, practically eliminating the dip entirely.

The PVB interlayer used in laminated glass, is, in fact, a resilient damping material, which helps to reduce the "coincidence dip". Normal PVB has a pretty decent effect in reducing the dip, but there are more expensive (and sometimes rather exotic!) interlayers that can do a better job at damping that resonance. As I said, it's usually not too much of an issue for home studios, since it is in a part of the spectrum that is already well isolated, usually. It only becomes significant for studios that are aiming for very high isolation, where each small improvement matters. Even them, there are things you can do to improve the situation, if you do have a coincidence dip problem.

Probably more than you needed to know! But interesting, nevertheless.


- Stuart -

[Soundman2020]

Source of the post Ok guys, another quick question specifically on insulation.

I built the exterior walls with 2x6. In each cavity I now have 2 layers of 5/8" drywall (1.25" total) and 3" bats of rockwool safe and sound. This leaves about 1" of space in the 2x6's that is unfilled. I then laid out my inner leaf with 2x4's with a 1" air gap from the outer walls. This gave me 2" of free air between layers of insulation. The inner leaf having 3" bats of rockwool safe and sound as well.

I'm not sure I have the picture right here: What is the total depth of the air cavity? In other words, if you could put a tape measure inside the wall and measure between the faces of the inner leaf and outer leaf, what distance would that be? If I'm understanding right, you have two 2x6 stud frame separated by an inch, so the total possible depth was 5.5 + 1 + 5.5 = 11". Then you "beefed up" between the studs, using up 1.25" on each side, total 2.5 reduction, so now you have 11 - 2.5 = 8.5" depth for the cavity. Is that correct? Then you have 2 layers of 3" thick batts, so there's 8.5 - 3 - 3 = 2.5" or empty air in there?

Did I get that correct?

If so, then putting more insulation in that empty air would help with isolation, yes.

Here's a graph that shows the effect of different amounts of cavity fill. It's for Isover fiberglass wool, not your mineral wool, so the effects are not going to be the same, but the principle still holds.

As you can see, there's a difference of maybe 16 dB in isolation between a wall that has no insulation, and one that is completely filled. Each additional inch improves the isolation.

There are several things that the insualtion does, all at once, to improve isolation.

1. It lowers the MSM resonant frequency of the entire wall.
2. It damps sound waves traveling through the wall
3. It damps resonance inside the cavity (standing waves in the vertical and horizontal planes)
4. It reduces the speed of sound inside the wall

All of those are good for isolation, so the more you can get in there, the better it will be.

However, do not compress your insulation! Just lay it in to its natural depth. Compressing it a little is OK, but don't overdo it. If you compress it, you run the risk of maybe creating flanking paths through the insinuation itself. Compressing it also changes the density (obviously!), and higher density insulation is WORSE for low frequency isolation (beyond a certain point, of course).

... put pink fluffy cavities as well to improve isolation. I can do this, but I did not budget for it so it would be over and above what I am already over and above. Additionally, the only insulation I can find (r13-r19 is faced insulation.

You can't get ordinary pink fluffy, or equivalent where you live? Pretty much any type of light weight fiberglass wool insulation will do here.

2. If the benefit really is there, does it matter if there is a vapor/paper barrier in the middle of the wall attached to the face of the 2x6 studs? Wouldnt this actually decrease the resonance attenuation because it is a semi stiff surface?

It might change the acoustic characteristics, yes, but more importantly you should never have two vapor barriers in your wall! Only one. I'd suggest looking around more, to see what other insulation you can find. Pink-fluffy type insulation is fairly common.

- Stuart -

[eightamrock]

Source of the post

Source of the post Ok guys, another quick question specifically on insulation.

I built the exterior walls with 2x6. In each cavity I now have 2 layers of 5/8" drywall (1.25" total) and 3" bats of rockwool safe and sound. This leaves about 1" of space in the 2x6's that is unfilled. I then laid out my inner leaf with 2x4's with a 1" air gap from the outer walls. This gave me 2" of free air between layers of insulation. The inner leaf having 3" bats of rockwool safe and sound as well.

I'm not sure I have the picture right here: What is the total depth of the air cavity? In other words, if you could put a tape measure inside the wall and measure between the faces of the inner leaf and outer leaf, what distance would that be? If I'm understanding right, you have two 2x6 stud frame separated by an inch, so the total possible depth was 5.5 + 1 + 5.5 = 11". Then you "beefed up" between the studs, using up 1.25" on each side, total 2.5 reduction, so now you have 11 - 2.5 = 8.5" depth for the cavity. Is that correct? Then you have 2 layers of 3" thick batts, so there's 8.5 - 3 - 3 = 2.5" or empty air in there?

Did I get that correct?

If so, then putting more insulation in that empty air would help with isolation, yes.

Here's a graph that shows the effect of different amounts of cavity fill. It's for Isover fiberglass wool, not your mineral wool, so the effects are not going to be the same, but the principle still holds. effect-of-various-wall-cavity-insulation-fill-percentages.png As you can see, there's a difference of maybe 16 dB in isolation between a wall that has no insulation, and one that is completely filled. Each additional inch improves the isolation.

There are several things that the insualtion does, all at once, to improve isolation.

1. It lowers the MSM resonant frequency of the entire wall.
2. It damps sound waves traveling through the wall
3. It damps resonance inside the cavity (standing waves in the vertical and horizontal planes)
4. It reduces the speed of sound inside the wall

All of those are good for isolation, so the more you can get in there, the better it will be.

However, do not compress your insulation! Just lay it in to its natural depth. Compressing it a little is OK, but don't overdo it. If you compress it, you run the risk of maybe creating flanking paths through the insinuation itself. Compressing it also changes the density (obviously!), and higher density insulation is WORSE for low frequency isolation (beyond a certain point, of course).

... put pink fluffy cavities as well to improve isolation. I can do this, but I did not budget for it so it would be over and above what I am already over and above. Additionally, the only insulation I can find (r13-r19 is faced insulation.

You can't get ordinary pink fluffy, or equivalent where you live? Pretty much any type of light weight fiberglass wool insulation will do here.

2. If the benefit really is there, does it matter if there is a vapor/paper barrier in the middle of the wall attached to the face of the 2x6 studs? Wouldnt this actually decrease the resonance attenuation because it is a semi stiff surface?

It might change the acoustic characteristics, yes, but more importantly you should never have two vapor barriers in your wall! Only one. I'd suggest looking around more, to see what other insulation you can find. Pink-fluffy type insulation is fairly common.

- Stuart -

Thanks Stuart, let me clarify.

My wall assembly is 2x4 inner leaf, 2x6 outer leaf (exterior wall) separated by 1” of air gap.

In the 2x6 wall, the outer face has 1/2” ply wood, tyvek, and vinyl siding. In 2x6 wall cavities pressed against the 1/2” outer sheathing is 2 layers of 5/8” drywall. Pressed against that is 3” thick rockwool.

5.5” - 3” - 1.25” = 1.25” of depth left to fill in the 2x6 cavity.

Then there is my 1” air gap, and a 2x4 wall assembly for the inner leaf. This will have only the 3” rockwool in the cavities and 2 layers of 5/8” on the face.

3.5 - 3 = .5”

So .5” + 1” + 1.25” = 2.75” of space I could try to fill.

My mass to mass measurement is 3.5 + 1 + 4.25 = 8.75”.

So is it worth it to try and compress some R 13 in that 2.75” gap?

Also I can get pink fluffy, I just need to special order it unfaced. They only sell it with the paper backing around here.

In total I have 2.5” of mass, green glue, 6” of rockwool Im my wall assembly with a total air gap of 8.75”

[gullfo]

i would try to get the unfaced R-13 in there.

[eightamrock]

Source of the post i would try to get the unfaced R-13 in there.

Is there a benefit to buying R-19 and using that on the 2x4 wall instead of rockwool? This way the vapor barrier is in the right place, and I get another 6”inches of insulation. It would poke through the 2x4 frame and touch the 2x6 frame.

[gullfo]

depending on the rockwool product density - you might even put a layer of the rockwool into that air space. you have 8-3/4" air, and 9" of rockwool.

[Soundman2020]

Source of the post you might even put a layer of the rockwool into that air space. you have 8-3/4" air, and 9" of rockwool.

Yup. That's only very slight compression: not gonna cause any flanking. That would work fine.

- Stuart -

[eightamrock]

Edit: I tool the pictures in portrait and the site is converting them to landscape... not sure how to fix that. Sorry.

Windows update, sealed sealed and sealed again.

The window stops are actually 1x1 that are dado'd into the 1x8's so a 1/2" in revealed. I then glued and nailed the 1x1's into the frames. SO there is no air that can pass directly through anywhere on this. I also dado'd the edges 1/4" and inset the corners.

I then primed with exterior primer, painted 2 coats of benjamin moore exterior aura paint.

The windows were made 1/4" short of the width and length of the frames. This gave me 1/8" all the way around to add a nice thick bead of silicon under the outer stops.

First, I added the glazing tape. (This stuff is sticky and hard to work with) I used 3/8" x 1/16" all the way around the stops. Using 1/8" tile spacers around the edge made sure I placed the window exactly center of the frame. Also these huge suction cup handles from amazon really helped. They were $30 and well worth what I paid.... I placed the window in the frame and applied pressure around the outside to make sure it really set into the glazing tape.

Second, I caulked a bead of exterior window and door caulk into the 1/8" gap all the way around the window. I made sure that this was overflowing a bit so when I set the exterior stops in (1/2" vinyl quarter round) it made a nice third water and air barrier for the window.

Lastly, after tacking the out stops in place I put another bead of caulk around the edge of the outer stops, and then another clear bead on inner edge against the glass.... Lots and lots of work. 1 down 5 to go.

[eightamrock]

Better upright photos.