The bass player's Music Room

[Ray Growl]

Hello to all
I’m building a music room!
I'm a bass player and designer of bass cabinets living in Mexico City. The purpose of this space is to have a somewhat "neutral playground" for trying and testing new bass cabinets designs and also to rehearse with my rock band. Eventually it could serve as a one room studio to record song mockups and demos. Soundproofing will be a top priority because this is a very quiet residential area. However, I will allocate most of the resources (money, time etc.) to make this room a great sounding bass room.

Available space.
I am buying house refurbished from a 10 years old one. The general lay out of first and second floors won’t change so I have no other choice than the third floor to build my music room. In fact the room’s “shell” is already built. It was a better deal to just build a few more walls and a roof adding to the price of the house and pay for everything with the mortgage. I asked the constructor to just raise the walls with red (solid) brick as the rest of the house. No electrical wiring, no lightning just walls (Q1). The roof is light poured concrete (10 cms. approx. with 2 concrete and steel Beams running across) and the floor is the roof of the master bedroom below.
The entire house is in no physical contact with the neighbor’s at the right (the side the music room will be) but it touches the house at the left. Every building having their own wall obviously but they are adjacent.
Due to the old shape of the house and a large dome that gives natural light to the main stairs. I'm limited to a quasi-rectangular shape of about 40m2 (430 ft2). Height goes from 2.8 m to 3m (see attached images).

Soundproofing requirements.
How loud it is going to be inside? Well, for band practicing we have measured (sound meter with C weighting and slow reading) levels of about 100dB with drums, bass, two guitars and vocals. We are not teenagers anymore so we really fight ourselves to turn down the knobs. For bass cabinets testing, levels could go up to 120 dB. Maybe more for a few seconds. Everything from sweeps, bursts and pink noise to hard playing bass at top volume and speakers driven to blow up.
Outside the room in the open space things are very quiet, occasional dog barking but no trains or factories. The loudest noises I can expect will come from my daughters playing inside the house or in the garden. Sound coming in is not an issue. Real problem is the sound I’m going to be doing inside. Noise floor can go as low as 35 dB outside averaging 40 dB so that gives a huge gap of 80 dB to tame. For what I read in this forum that level of sound reduction would not be practically attainable. Regulations in México set the maximum noise emission from a fixed source to 68 dB from 6 AM to 10 PM and 65 dB from 10PM to 6 AM. So I will have to make the loudest noises at decent hours.
As I mentioned before, the walls are standard red brick rendered on the outside. (Q1 ) According to this STC chart http://johnlsayers.com/Recmanual/Pages/STC%20Chart.htm I already have STC of something between 39 and 45 assuming doors and window are perfect. After reading some comments from Stuart (soundman2020) in other posts I understood that STC has little to do with decibels so I will not try to subtract STC from SPL (Q2 ).
Let’s set a target of 60dB of sound reduction for now. That would take long band rehearsals down to tolerable levels for neighbors and wife. Also loudest bass cabinet testing would comply with local regulations.

Design / Construction stage:
Design is in a very early stage. We are planning to move in late October, then I will be able to actually measure things properly (if Q2 has a practical answer). First move will be the window and doors for the outer shell.

The hole for the Window is 1.1m x 1.65m. I’m considering an off the shell German style window with PVC frame. They come with single or double glass from 3 up to 35mm. I have used them in an apartment in a very noisy environment with great results. They are residential products, not designed for studios but at least you have the possibility to customize them. Manufacturer uses a sort of TL figure called “Indice de reducción Sonora” Rw showing a value of -33dB for a single glass 12mm (Q3 )

Door will be double also, 2 high mass solid door and frames, one directly against the existing vain (not sure that is the right word) and the other built in to the interior wall. I will provide more details on this later.

BUDGET: USD $15,000 for window, doors and interior floor walls and ceiling. My contractor gave me a number of about $5,000 for the walls and ceiling for a normal (with no acoustic knowledge or special care) construction. I will allocate more money as the project develops (according to my ability to raise more founds obviously).

Next to design/think about/ask/buy/build:
- Flooring- Only thing decided by now is that a floated floor is out. May be just regular laminated floor of any kind over a layer of 19mm plywood or Particle board, resting on this 6mm acoustic foam http://www.aislantesmexico.com.mx/piso-acustico.html
- Interior Walls- Inside the room I will raise another leaf (15 cm apart from the outer wall) consisting of: wood or steel framing (undecided yet), insulation, ½” drywall, green glue, ¾” drywall. (Q4/Q5 )
- Electric installation and lightning
- Room Lay-out: drums, amps, Mini PA position for best possible sound inside the room
- Bass clarity focused Acoustic conditioning (Bass traps, Absorbers, etc) (Q6 )

I understand there is a huge amount of work ahead. By now I would like to receive your kind comments and suggestions about all above and the following (very basic) questions.

QUESTIONS

Q1.- Painting the interior of the brick walls is of any benefit? They will end hidden anyway but, Do you think the sealant effect of the paint could give any gain in STC? Almost 90m2 to cover. Worth the effort?

Q2.- How do you measure how much sound you are blocking with every step? I have an SPL meter, REW software, calibrated measurement mic etc. Should I just play loud pink noise inside, close the door and measure outside with an SPL meter? Any standard for this?

Q3.- So we don’t want to create a sound leaking window right? How do I calculate the minimum thickness of the glass to compare with the 15 cms solid brick wall?

Q4.- Are 15cm of air between leafs enough?

Q5 Should I rest the interior wall on the floor? Or directly against the concrete below? Which way is easier to build / Seal.

Q6.- What do you think about the shape of the room? There is no much to do in that regard because of the loading points distributed around the plants below. Is it better or worse than a rectangular room? Is it going to be a nightmare of acoustics? I have Everest’s “Master Handbook of Acoustics” and Gervais’s “Build it like the pros“ Waiting for some free time to be read. As of now, my limited knowledge on the subject only let me see more corners to put bass traps.

I really look forward to read your comments. I'm very excited and willing to go the extra mile with this project!

Ray

Music Room Ext Walls.jpg

[Soundman2020]

Hi Ray, and welcome again! Glad to see you starting your thread, y muy bienvenido al foro!

You have a nice sized room there, with good height, and a rally good outer leaf. You should be able to get quite decent isolation from that, and decent acoustics too. The strange shape doesn't matter too much, since this is just a music / rehearsal / cab testing room. The shape would be a problem if this were intended as a control room, but that isn't the case, so you are good.

so I have no other choice than the third floor to build my music room.

That's a bit of a problem, since upper floors are harder to isolate. Ground floor rooms have the benefit of having the slab damped by the entire planet, while upper floors are not damped at all. so your floor is going to need special attention...

we have measured (sound meter with C weighting and slow reading) levels of about 100dB with drums, bass, two guitars and vocals. We are not teenagers anymore so we really fight ourselves to turn down the knobs. For bass cabinets testing, levels could go up to 120 dB.

It's good to have realistic objective numbers to work with! Too many people just come up with "we are loud, how do we make it quiet?", and that's useless. So it's great to see your numbers.

Maybe more for a few seconds. Everything from sweeps, bursts and pink noise to hard playing bass at top volume and speakers driven to blow up.

"blow up"? Mmmm.... Wow! The actual explosion part might not be well isolated.... and I do hope there's nobody inside the room when that happens! I think this is a first for the forum: somebody actually wanting to intentionally blow up things in their studio... Cool! I love a challenge!

Noise floor can go as low as 35 dB outside averaging 40 dB so that gives a huge gap of 80 dB to tame.

80 dB is a tall order. Not impossible, but not easy, and not cheap.

For what I read in this forum that level of sound reduction would not be practically attainable.

On a limited budget, and an upper floor: correct. IT COULD be done, but the cost would be stratospheric.

Regulations in México set the maximum noise emission from a fixed source to 68 dB from 6 AM to 10 PM and 65 dB from 10PM to 6 AM.

Those are VERY generous limits! I'm also surprised that there's only 3 dB difference between day and night? Strange. If your limit is 65 dB, and your peak is 120 dB, you'd only need 55 dB of isolation, which is entirely do-able. But 65 dB outside is still pretty loud...

I already have STC of something between 39 and 45 assuming doors and window are perfect.

Sounds about right for that construction, but "assuming doors and window are perfect" is a big assumption!

After reading some comments from Stuart (soundman2020) in other posts I understood that STC has little to do with decibels so I will not try to subtract STC from SPL

Yup! That's like subtracting 5 apples from 15 oranges, and deciding that the answer is 12 bananas and four grapes...

Let’s set a target of 60dB of sound reduction for now.

That's a reasonable goal, and do-able.

The hole for the Window is 1.1m x 1.65m. I’m considering an off the shell German style window with PVC frame.

PVC frames are usually hollow inside: it's just a thin "web" of PVC on each side, with some internal strengthening ribs, but there's not a lot of mass in there. So even though the glass itself might be great, the frame might not be. Are there any solid wood frame options available in México? If not, then you might have to build them yourself. It's not too hard, actually.

They come with single or double glass from 3 up to 35mm.

Get single-pane, nit double-pane. With double-pane glass in each of your two windows, you'd end up with a 4-leaf isolation system, which is not good for low frequencies (such as loud bass cabs!).

Manufacturer uses a sort of TL figure called “Indice de reducción Sonora” Rw showing a value of -33dB for a single glass 12mm (Q3 )

Rw is a valid way of measuring transmission loss. Similar to STC, it is a single-number rating system, and similar to STC it only takes into account the middle section of the audio spectrum. 33 for 12mm glass sounds about right, but it would be good if they would quote the Rw+Ctr numbers as well. The Ctr modifier taks into account some low-frequency sounds as well. In essence, it "punishes" the Rw number by subtracting another number from it, to give a more realistic overall number when low frequencies are involved. the "Ctr" factor might be about 5 to 15 points, depending on construction.

Door will be double also, 2 high mass solid door and frames, one directly against the existing vain (not sure that is the right word)

"leaf"?

May be just regular laminated floor of any kind over a layer of 19mm plywood or Particle board, resting on this 6mm acoustic foam

That's a reasonable plan for low to medium isolation, but I think you might need more than that for your case, as most of your sound energy is in low frequencies. You need to prevent those from getting into the building structure.

- Interior Walls- Inside the room I will raise another leaf (15 cm apart from the outer wall) consisting of: wood or steel framing (undecided yet), insulation, ½” drywall, green glue, ¾” drywall

It would be better to go with 3/4" + 3/4" drywall. There's no need to use different thicknesses: you need as much mass as possible in your walls, so go with 2 layers of the thickest stuff. Either wood or metal for your framing is fine. personally, I prefer wood.

Q1.- Painting the interior of the brick walls is of any benefit? They will end hidden anyway but, Do you think the sealant effect of the paint could give any gain in STC? Almost 90m2 to cover. Worth the effort?

Absolutely yes! Very much so. Brick and concrete are very porous, meaning that air can penetrate quiet a lot. Painting the surface seals all the tiny air "holes", creating a hermetic "air-proof" surface. One good option is to use "sellante de cal" if you can get it in México. If not, any good masonry sealer will work. You don't need an expensive paint: just something that seals up the pores really well, and won't peel or flake.

Q2.- How do you measure how much sound you are blocking with every step? I have an SPL meter, REW software, calibrated measurement mic etc. Should I just play loud pink noise inside, close the door and measure outside with an SPL meter? Any standard for this?

Yes. No. Maybe. Sometimes. Always. Never... !!! Not very helpful, I know... But there are different aspects to it. What you need to measure to judge actual transmission loss for typical conditions is to play loud rock music on a full-range speaker system at the same level that you expect to have in the room, so roughly 100 to 120 dB, measured "C" weighted, slow response, at about 1m from the speakers. (Wear ear protection! Those levels are harmful....). Play several different songs like that, and measure the levels, both average and peak. Then play the same set of songs while you are outside the room, and measure about 1m from the wall, also "C" weighted, slow response. The difference between those two numbers is a tough estimation of how much transmission loss you are getting, and since "C" weighting is a good reflection of how humans perceive loud sounds, that shows you a good estimate of the subjective level that people would judge. It's the best way to get a realistic "real world" measure.

But that's not what the regulations measure! Most noise regulations specify "A" weighting, which is good for you because "A" is less sensitive to low frequencies than "C". For bass-heavy music, there can be a big difference. You can see this yourself by flipping the meter from "C" to "A": the reading will drop quite a bit for typical rock music, but won't change at all for typical voice conversations.

So if you want to keep a record of how well things are changing as you build, start out by measuring with both "A" and "C" using loud music with the room exactly as it is now, then measure again in the same way, using the same music, at each stage: after putting the window and outer-leaf door in, after sealing the outer leaf, after putting the first layer of drywall on the inner-leaf, after putting the second layer on, after putting the inner-leaf door and window in, after putting the HVAC silencer boxes in, after final sealing of the inner-leaf, etc. The big changes will be apparent as you completely seal the outer leaf. then again as you completely seal the inner leaf, with smaller changes for the other steps.

You cold also measure with sine sweeps at each stage using REW, which would give you a more "scientific" measurement of isolation, and would also highlight any resonances that might be happening in the isolation system. That would add an extra level of isolation checks, and it would give you more objective graphical representations of TL. This would be the most accurate measure.

Using pink noise is not that good, as it is hard to distinguish low-level pink noise from background noise...

Q3.- So we don’t want to create a sound leaking window right? How do I calculate the minimum thickness of the glass to compare with the 15 cms solid brick wall?

In theory, the glass needs to be the same surface density as the leaf it is in, but in reality there isn't much point going beyond about 25mm thickness in glass, as it gets to be way expensive, and the very high cost can't be justified by the small extra increases in isolation. So if you put in something like 12+12 laminated glass with acoustic PVB, or even 10+10 with acoustic PVB, you'd be doing really well. For the inner-leaf wall, you could use something a bit thinner, such as maybe 8+8, or 6+10, or something in that range.

Q4.- Are 15cm of air between leafs enough?

Enough for what? Theoretically, you'd get about 63 dB of isolation from that system, it would isolate from about 27 Hz upwards, and you'd have good isolation above about 39 Hz. That's pretty darn good!

Q5 Should I rest the interior wall on the floor? Or directly against the concrete below? Which way is easier to build / Seal.

The inner-leaf wall should rest directly on the concrete slab. Seal the sole plate to the slab with three beads of good-quality caulk: one bead down the middle of the sole plate, and one bead an inch to each side of that. Then add another bead under each layer of drywall: put a shim under the sheet of drywall to create a gap, then nail / screw the drywall in place, then pull out the shim and seal the gap with backer rod and caulk.

Q6.- What do you think about the shape of the room?

It's fine. It would not be good for a control room, but for what you want it is great.

- Stuart -

[Ray Growl]

Hi Ray, and welcome again! Glad to see you starting your thread, y muy bienvenido al foro!

Big Thanks Stuart, I really appreciate your time. I will address each one of the issues you pointed out in a sequence taking your previous post as reference. So let’s start with the window.

The hole for the Window is 1.1m x 1.65m. I’m considering an off the shell German style window with PVC frame.

PVC frames are usually hollow inside: it's just a thin "web" of PVC on each side, with some internal strengthening ribs, but there's not a lot of mass in there. So even though the glass itself might be great, the frame might not be. Are there any solid wood frame options available in México? If not, then you might have to build them yourself. It's not too hard, actually.

They come with single or double glass from 3 up to 35mm.

Get single-pane, nit double-pane. With double-pane glass in each of your two windows, you'd end up with a 4-leaf isolation system, which is not good for low frequencies (such as loud bass cabs!).

Manufacturer uses a sort of TL figure called “Indice de reducción Sonora” Rw showing a value of -33dB for a single glass 12mm (Q3 )

Rw is a valid way of measuring transmission loss. Similar to STC, it is a single-number rating system, and similar to STC it only takes into account the middle section of the audio spectrum. 33 for 12mm glass sounds about right, but it would be good if they would quote the Rw+Ctr numbers as well. The Ctr modifier taks into account some low-frequency sounds as well. In essence, it "punishes" the Rw number by subtracting another number from it, to give a more realistic overall number when low frequencies are involved. the "Ctr" factor might be about 5 to 15 points, depending on construction.

Q3.- So we don’t want to create a sound leaking window right? How do I calculate the minimum thickness of the glass to compare with the 15 cms solid brick wall?

In theory, the glass needs to be the same surface density as the leaf it is in, but in reality there isn't much point going beyond about 25mm thickness in glass, as it gets to be way expensive, and the very high cost can't be justified by the small extra increases in isolation. So if you put in something like 12+12 laminated glass with acoustic PVB, or even 10+10 with acoustic PVB, you'd be doing really well. For the inner-leaf wall, you could use something a bit thinner, such as maybe 8+8, or 6+10, or something in that range.

I talked to a few vendors of "soundproofing" windows here in Mexico. They all only seem to carry the standard products of the brand they represent. They all have their STC numbers and recommend by heart the double glazed PVC frames.
I will then have to take your suggestion and make the windows myself. Very simple design using hard ash, oak or Tzalam. For the glass I will be using a 12+12mm laminate with 1.5mm PVB. Completely sealed with neoprene it should be better than the ones I could have bought. I estimate a total of $300 USD for the hole window.

Ventana Music Room.png

I also found an acoustic caulk available:

USG Acoustic Sealant.jpg

I'll try to tight fit the frame to the wall. Secure it with screws and caulk all the perimeter. The only thing I need to find is good hinges to carry the heavy load.

That is all for now. Not much I know
I'll post again to show the window construction, If everything goes well, next step will be the door.

Ray

[Soundman2020]

I will then have to take your suggestion and make the windows myself. Very simple design using hard ash, oak or Tzalam. For the glass I will be using a 12+12mm laminate with 1.5mm PVB. Completely sealed with neoprene it should be better than the ones I could have bought.

Great! But your sketch seems to show it as an operable window (one that can open). Not allowed! it must be fully sealed, and non-openable.

I also found an acoustic caulk available:

Yup, that's the USG stuff. A sticky, mucky pain to work with, but it does the job!

The only thing I need to find is good hinges to carry the heavy load.

nope. No hinges, because it cannot open....

- Stuart -

[Ray Growl]

Great! But your sketch seems to show it as an operable window (one that can open). Not allowed! it must be fully sealed, and non-openable.

Stuart, I don't want to be a smart*ss but... What you think of this double sealed frame? I've seen that design used for doors. I supposed it would work for a window too.

Double seal frame widow.jpg

I'm aware of the importance of the "airtightness" of the room leafs but it would be really good to be able to operate that window because a proper HVAC is not in my near plans. I'm thinking that frequent pauses to open doors an window during rehearsals would renew the air inside. Door and window are on oppsite sides of the room and a strong air flow is created naturally. Cooling the room inside could be adressed with a mini split unit. Edit: not quite sure about the mini split after reading this: http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=644

The laminated glass is already paid and cut, I'm picking it up this coming saturday, So:

What are my options now?
1.- Adjust mi window plans to make it a sealed non operable one using the glass I allready paid and use a fan at the door during brakes to renew air.

2.- Number 1 + design and install all the pipes and "silencer boxes" that later could become a propper HVAC system. Kind of leaning to the proposed solution for a DIY HVAC posted on as a stickie (already linked above).

3.- Continue with my plan ignoring your advice with the risk of not doing it right and getting no more help from this forum. (Insert your favorite adagio here)

Some very interesting threads under study in the following days:
http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=644
http://www.johnlsayers.com/phpBB2/viewt ... start=1365
http://www.johnlsayers.com/phpBB2/viewt ... 21&start=0

This forum is amazing!
Ray

[Soundman2020]

What you think of this double sealed frame? I've seen that design used for doors. I supposed it would work for a window too.

It's better than nothing, but still not as good as a fully-sealed window that is not operable.

because a proper HVAC is not in my near plans.

Then a proper studio is also not in your plans! Sorry to be so direct and harsh, but that's the simple truth. The HVAC system controls temperature, and also humidity. It is not a luxury: it is part of the basic design of a studio. You cannot have the windows open while you and your band is jamming in there, obviously, and I'm not sure if you have every been inside a small air-tight room with half a dozen hot, sweaty musicians that just ate pizza and drank beer, while the are jamming away happily.... It's not a nice place to be!

You need HVAC. It is not an optional extra. It is a requirement. Trying to ventilated and cool by just opening the windows is not only a bad, idea, it actually wont work!

I'm thinking that frequent pauses to open doors an window during rehearsals would renew the air inside.

You are thinking wrong! Don't think that way. Instead, think "small mini-split system, ducts, silencers, fans". That's the only realistic solution.

What are my options now?
1.- Adjust mi window plans to make it a sealed non operable one using the glass I allready paid and use a fan at the door during brakes to renew air.

Yep. Easy and cheap to do!

2.- Number 1 + design and install all the pipes and "silencer boxes" that later could become a propper HVAC system.

Correct. That plus a small mini-split will do the job.

3.- Continue with my plan ignoring your advice with the risk of not doing it right and getting no more help from this forum.

I wouldn't be worried about not getting more help from me! I'd be worried about spending a lot of money on a studio that doesn't work, and where nobody wants to play! A hot, stuffy, smelly, damp, room is not a place where musicians will like to be making music....


- Stuart -

[Ray Growl]

What you think of this double sealed frame? I've seen that design used for doors. I supposed it would work for a window too.

It's better than nothing, but still not as good as a fully-sealed window that is not operable.

because a proper HVAC is not in my near plans.

Then a proper studio is also not in your plans! Sorry to be so direct and harsh, but that's the simple truth. The HVAC system controls temperature, and also humidity. It is not a luxury: it is part of the basic design of a studio. You cannot have the windows open while you and your band is jamming in there, obviously, and I'm not sure if you have every been inside a small air-tight room with half a dozen hot, sweaty musicians that just ate pizza and drank beer, while the are jamming away happily.... It's not a nice place to be!

You need HVAC. It is not an optional extra. It is a requirement. Trying to ventilated and cool by just opening the windows is not only a bad, idea, it actually wont work!

I'm thinking that frequent pauses to open doors an window during rehearsals would renew the air inside.

You are thinking wrong! Don't think that way. Instead, think "small mini-split system, ducts, silencers, fans". That's the only realistic solution.

What are my options now?
1.- Adjust mi window plans to make it a sealed non operable one using the glass I allready paid and use a fan at the door during brakes to renew air.

Yep. Easy and cheap to do!

2.- Number 1 + design and install all the pipes and "silencer boxes" that later could become a propper HVAC system.

Correct. That plus a small mini-split will do the job.

3.- Continue with my plan ignoring your advice with the risk of not doing it right and getting no more help from this forum.

I wouldn't be worried about not getting more help from me! I'd be worried about spending a lot of money on a studio that doesn't work, and where nobody wants to play! A hot, stuffy, smelly, damp, room is not a place where musicians will like to be making music....


- Stuart -

Hi there!
Thanks again for your answer Stuart!
I can’t believe three months passed from my first post. We finally moved in to the new house. Everything is a mess obviously and my spare time has been used to unpack the essential survival goods, put washing machines to work and hang mirrors and pictures. This place is VERY QUIET!

Regarding the music room I have decided not to take any shortcut and do things right from the first time. I will do the sealed window and plan with the ventilation system and mini split in mind before I cut the first piece of wood. So let’s forget about the window and door for a moment and start to see what I actually have. The walls, ceiling and floor.

These are my first calculations.
The walls of my room are solid brickwall rendered one side. According to “empirical mass law” (posted here http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=20660 by Stuart) [L = 14.5 log (Ms * 0.205) + 23 dB] where Ms (surface density) is about 240 Kg/m2, the empirical TL for my walls would be 48dB aprox.
However, being this a BASS room, bass frequencies are a big concern.
Using the mass law (not empirical one) TL(dB)= 20log(W) + 20log(f) -47.2 I’m getting TL estimates of 42dB @ 125Hz, 36 @ 63Hz and 30dB @ 31 Hz. Not too much!

Mass-Air-Mass system:
According to the formulas in the previously linked post, I did the math for 6 different options for the double wall construction (I used this formula Fc=c[(m1+m2)/(m1m2d)]^.5 to calculate the resonance frequency with c=43 assuming the air gap is filled with the proper material).

Opt 0 Outer leaf (Do nothing).
Opt 1 One layer 12mm drywall Airgap=10cm
Opt 2 One layer 16mm drywall Airgap=15cm
Opt 3 2 layers 12mm drywall Airgap=15cm
Opt 4 2 layers 16mm drywall Airgap=15cm
Opt 5 1 layers 16mm drywall Airgap=25cm
Opt 6 2 layers 16mm drywall Airgap=25cm

first TL calcs.png

Figures in the lower chart are estimates just for comparison purposes. Cost are in Mexican pesos and include materials and labor only for the frames and walls.
It’s clear that having a lower resonance of the system is Key. 31 Hz is going to be hard in any situation. So I will focus in the much critical 63Hz -250Hz range for bass cabinets design and testing. Option 6 obviously is the best in terms of TL but, Loosing 10 m2 of usable space inside is not nice though. Also, I’m going to have a conversation with my architect to find out if this 3rd floor can handle 2.5 tons of additional weight!
Those were the calculations for walls only. Celling could be expected to have better TL because there is more mass in the outer leaf (20 cms concrete slab). So biggest concern would be… Yes the FLOOR!
Flor is a 30 cms concrete slab on a third floor (over my bedroom). Considering a surface density of 2,000 Kg/m3 (TBC). The empirical TL would be 53dB… BUT! TL values according to mass law are 50dB @ 125Hz, 44dB @ 63Hz and 38dB @ 31 Hz.
So if the lowest value wins when it comes to combine TL’s of the different surfaces and assuming I can do Option 6 (2 Layers of 16mm drywall With an airgap of 20 cms. My predicted TL curve would be the red one (with dots) in the graph below.

Minimun TL graphs.png

(sorry there is a typo in the legend of the chart, the red line with dots represents the minimun values for Floor and Option 6).

So here come the questions!!

1.- It seems that my floor is pulling down the curve from 63Hz and above. I’m 10dB short on the 60dB target at 125Hz. I’ve seen some “acoustic” foamy layers that are supposed to add 21dB of sound reduction when used between the slab and a regular laminated mdf flooring. But the manufacturer shows figures only from 250 Hz and above. ¿What can I do to improve TL of my floor between 63 and 125? Not thinking about floating the floor but I’ve seen some interesting drum platforms around here that can be used as amp stands also.
2.- Below 50Hz the wall is guilty of low levels of TL. What about green glue? Is there any benefit in this region? How can I incorporate than effect -if any- in the calculations?
3.- Am I aiming too high with the 60dB target for the low bass frequencies considering the limitations of this room being in a third floor?
4.- Flanking noise coming through the connection of the inner leaf walls directly to the outer leaf floor.

AirandFlankNoiseTransThFloor.jpg

¿Nothing to do about it?

Ray

[Soundman2020]

Regarding the music room I have decided not to take any shortcut and do things right from the first time.

I will do the sealed window and plan with the ventilation system and mini split in mind before I cut the first piece of wood.

Very smart move!

The walls of my room are solid brickwall rendered one side. According to “empirical mass law” (posted here viewtopic.php?f=2&t=20660 by Stuart) [L = 14.5 log (Ms * 0.205) + 23 dB] where Ms (surface density) is about 240 Kg/m2, the empirical TL for my walls would be 48dB aprox.

Right. That's a pretty good starting point.

Using the mass law (not empirical one) TL(dB)= 20log(W) + 20log(f) -47.2 I’m getting TL estimates of 42dB @ 125Hz, 36 @ 63Hz and 30dB @ 31 Hz. Not too much!

It's not too bad, actually. Compare that against the Fletcher-Munson curves, and you'll see that human perception of that would not be too problematic.

Mass-Air-Mass system:
According to the formulas in the previously linked post, I did the math for 6 different options for the double wall construction (I used this formula Fc=c[(m1+m2)/(m1m2d)]^.5 to calculate the resonance frequency with c=43 assuming the air gap is filled with the proper material).

I assume you are using the figure of 240 kg/m2 for m1, and the relevant numbers in each case for m2?

When you say "air gap of 15cm", how are you considering that "air gap"? It should be from the surface of the brick wall across the entire cavity, and up to the surface of the drywall, regardless of the insulation. Is that what you did?

31 Hz is going to be hard in any situation. So I will focus in the much critical 63Hz -250Hz range

Right! And there not much happening at 31 Hz in any case.

Option 6 obviously is the best in terms of TL but, Loosing 10 m2 of usable space inside is not nice though.

Then use higher-density materials! And use Green Glue! As a test case, see what happens if you try a sandwich of 16mm OSB on the studs, then 16mm of fiber-cement board with Green Glue, an finally 16mm of drywall, with a 15cm air gap, completely filled with fiberglass insulation...

Also, I’m going to have a conversation with my architect to find out if this 3rd floor can handle 2.5 tons of additional weight!

Yep...

Flor is a 30 cms concrete slab on a third floor (over my bedroom). Considering a surface density of 2,000 Kg/m3 (TBC). The empirical TL would be 53dB… BUT! TL values according to mass law are 50dB @ 125Hz, 44dB @ 63Hz and 38dB @ 31 Hz.

Yes, but that's for airborne sound transmission, which is walls and ceilings, windows and doors. Floors have that too, but the also have the added issue of impact noise... so total isolation is lower.

You might want to consider doing a "drum riser" style of floor.

I’m 10dB short on the 60dB target at 125Hz.

Why do you want 60 dB at 125 HZ? That's a pretty steep goal to be aiming for!!! That would probably be something like 80 dB overal, which is VERY high isolation!

I’ve seen some “acoustic” foamy layers that are supposed to add 21dB of sound reduction

I've seen those too! And I've also seen multi-vitamins that are supposed to make me live in perfect health until I'm 150 years old, and light bulbs that are supposed to last for twenty years without burning out, and clothes that never wear out and never need washing... I'd classify all those things in the same category...

But the manufacturer shows figures only from 250 Hz and above.

Strange, isn't it? I wonder why? I'm sure it has nothing at all to do with the fact that it's dead easy to isolate about 250 Hz, and damn hard to do it from 200 Hz down! Nahh, that can't be the reason... I'm sure it's just a typo!

Not thinking about floating the floor but I’ve seen some interesting drum platforms around here that can be used as amp stands also.

It is also possible to expand the concept to cover the entire floor, if you do ti carefully, and if your building code allows it.

2.- Below 50Hz the wall is guilty of low levels of TL. What about green glue? Is there any benefit in this region?

Definitely! It works. And the low frequency part of the spectrum is where ti shows the most benefit.

How can I incorporate than effect -if any- in the calculations?

Green Glue themselves say that there product is roughly equivalent to adding an extra layer of drywall, but it's actually a bit better than that, since there¿'s real damping going on in the low end. So when you do your math, pretend that you have one extra layer of drywall in there, then add 1 or 2 dB in addition, for the lowest end.

3.- Am I aiming too high with the 60dB target for the low bass frequencies considering the limitations of this room being in a third floor?

As I mentioned above, that's a very high goal to be aiming for. Why do you need that much? Take a close look at Fletcher-Munson...

4.- Flanking noise coming through the connection of the inner leaf walls directly to the outer leaf floor.

There are ways of dealing with that too...

- Stuart -