John Sayers' Recording Studio Design Forum Archive

Hi everybody,
Hope you’re doing well seeing the current circumstances around the world!
To make the most out of a bad situation I’ve decided to design a drum space / studio where I can practice and record acoustic drums without bothering the neighbors and most importantly.. my girlfriend.

Looking for some feedback on the design as this will be my first build. A lot of research and posts on this forum and also on Gearslutz has already helped me gain a lot of knowledge and especially what NOT to do, however, I’m still not there.

I did already create a post on Gearslutz when I was in an earlier stage of this process.
post on Gearslutz
However, I noticed there are also some good experienced people on this forum and would like to see where this will get me.

Existing situation
Attached is a sketch of my situation where I live. There is a garage of about 16 meters long which is attached to a gym. On the others sides there is just garden and also the drive way. I’ll be using only a part of the garage as the drum room, sketch of the dimensions attached. All of the walls are masonry walls (cavity brick wall). It’s red brick 100mm thick, two layers with an air gap of approximately 50mm – 75mm. Not sure if the red brick is connected to each other but I would assume so.
The roof is a flat roof which has been recently repaired. While doing so I took the opportunity of also adding 25mm Fermacell drywall (suited for outside, density 1000 kg/m3) on to an 18mm underlayment plate. On top of those two layers is the roofing (moisture resistant plastic, thermo isolation and bitumen roof). Two windows are also located in the garage. Laminated glass approximately 25mm thick.

The floor is just tiles onto a concrete slab. One section of the room is raised a little bit as it was probably built onto at a later stage by previous owners. Where the room is raised there is also an iron beam in the ceiling they’ve placed to allow for additional building.

Requirements
Measurements have been done after sealing a lot of air gaps in the existing wall and also plugging the windows using a window plug. The window plug is an MDF plate of 22mm thick has been screwed onto a wooden frame screwed into the wall. Backer rod between frame and MDF plate to seal air tight. Inside the window I’ve placed some egg crate like foam which were readily available. See attached picture. I couldn’t put the window plug into the window as the handle is sticking out. Measurement equipment used:
UMIK-1 microphone
REW software Measurement show 115dB levels inside the garage while playing acoustic drums. Microphone 1.5 meters away from the drums. See attached measurement ‘2020-04-24_Peak drums inside long’. I've not attached the current (average) measurements as there's a file limit.

Measurement outside close to window 1 & 2.
‘2020-04-24_Peak drums outside window 1 long’ ‘2020-04-24_Peak drums outside window 2 long’ I’ve also used Yamaha HS8 active studio speakers playing music and also pink noise.
‘2020-04-19_Peak - Test inside 2 meters (Dark side - Muse)’ ‘2020-04-19_Peak - Test outside close to window 1 without plug (Dark side - Muse)’ ‘2020-04-19_Peak - Test outside 5 meters from window 1 without plug (Dark side - Muse)’ ‘2020-04-19_Peak - Test outside close to window 1 with plug (Dark side - Muse)’ ‘2020-04-25_Peak_Pink noise outside garage door’ Ambient noise levels around 35 – 40 dB.

I would like to bring the overall level down to 30 dB. To put it in another perspective, I would like to be able to play the drums at 11pm without bothering the neighbors.
For the low frequencies I would like to go as low as possible in reduction. I do need to fine tune this with also compromising what dimensions I’ll be left over with inside the room itself.

For example, some peak readings show an dB level of 65 – 75 between frequency range 40 – 80Hz. If possible I would like to reduce this to 30dB. I’m well aware that this is going to be a difficult task.

Draft concept of decoupled room
My first draft is to have a decoupled room as following:
New walls facing existing brick wall
- Existing brick wall
- Air gap of 75mm filled with fiberglass wool
- 100mm wooden or steel frame
- Two layers of 15mm fermacell drywall (1150 kg/m3)

I’ve used different MAM calculators and formulas to estimate the working frequency of this wall.
Working frequency MAM calc. John Brandt (JB): 15Hz – lowest working frequency (with porous absorber)
Assuming the wall is one leaf (which in reality it is not), two layers of brick with air gap of +/- 50mm, 160 kg/m2. Then the new drywall as second leaf.
I highly doubt that this is a right estimation.

Triple leaf partition formula is giving me 63Hz. (with porous absorber)
Using the MSM equation also provided by Soundman2020 (https://spartanew.digistar.cl/Forum/viewtopic.php?) I’ve used the constant of 43 with Metric figures as using the 1900 as proposed by Soundman is giving me odd numbers. Frequency of +1000 with high transmission losses.

For this partition it is hard to find good test examples. I could not find any test showing masonry and drywall. Only one close to it was on the IR 586, page 31, TL-88-440, they show test results of an cavity concrete wall. 90mm concrete, air gap of 60mm, fibre insulation, 90mm concrete, 1 layer of 16mm gypsum board.

New wall facing opening in garage
- Two layers of 15mm fermacell drywall
- 100mm wooden or steel frame
- Air gap of 75mm filled with fiberglass wool
- 100mm wooden or steel frame
- Two layers of 15mm fermacell drywall

Working frequency MAM calc. JB: 33Hz – lowest working frequency (with porous absorber)
Double leaf partition formula is giving me 46Hz (with porous absorber)

This is the ideal wall construction and should give me good transmission losses. IR 761 TL-93-308.

Ceiling
- Two layers of 15mm fermacell drywall
- Wooden joists interleaved between existing wooden joists
- Air gap of 10mm
- Existing wooden joists of 150mm in height
- Underlayment plate 18mm thick
- Fermacell drywall 25mm thick
- Roofing materials.

Working frequency MAM calc. JB: 35Hz – lowest working frequency (with porous absorber)
Double leaf partition formula is giving me 48Hz (with porous absorber)

Following the test of IR-761 these are some good references:
- TL-93-202 - TL of 56
- TL-93-233 - TL of 57 -> leaf 1 & 2 both have a mass of 23kg/m2 with an air gap of 140mm

I hope this description is clear enough. If not I’ll provide sketches.

Floor
I will not do any isolation on the floor as it’s already on a concrete slab.

Doors
Two doors will be needed, one on the inside and one on the outside layer. The door will be on the inner side wall of the garage. I did not spend time yet on the design of the door. As soon as I’ve finished design of the walls I’ll start with the doors.

Windows
I’ve decided to use no windows to maximize the sound isolation and reduce the budget required.

HVAC system
The HVAC system has not been designed yet. I do have some figures on what fresh air and cooling is required.
The idea is to have an air inlet and outlet on the inner wall of the garage going into the other section of the garage. This means it will take the air from inside also reducing the risk of sound leakage outside the building. The fresh air intake will be from the garage with is a room of approximately 6 x 3.5 x 2.8 meters (L x B x H), there is also a window in this room.
See attached sketch ‘Layout garage, HVAC system’.

An air cooler (probably split unit) will be installed with the compressor assembled on the roof.

Budget
I’ve not got a real budget down yet but I’m willing to spend € 5000.- if required.

Questions

- The masonry brick wall is causing a three leaf system with the inner wall?
- Should I leave the window plugs in or remove them before building the room within a room?
- Wooden vs steel frame? Any ideas? I’ve read a steel frame is slightly better in reduction. It’s also easier to assemble.
- Any feedback on the frequencies and transmission losses? What results would it give me if I went for three or even four layers of drywall on the inside?
- Any feedback on the HVAC system? Any concerns with having the fresh air in- and outtake located on the inside of the garage? Feedback and comments much appreciated!

- The masonry brick wall is causing a three leaf system with the inner wall?

Yes and no. There is a cavity in them but they are still acting as a single unit... just with a resonant chamber in them. Sucks but it is what it is.

- Should I leave the window plugs in or remove them before building the room within a room?

You need a complete outer leaf that has great mass so yes, it needs to be plugged. Have considered using brick to plug it?

- Wooden vs steel frame? Any ideas? I’ve read a steel frame is slightly better in reduction. It’s also easier to assemble.

In my opinion, wood. Steel framing is super flimsy and hard to manipulate.

- Any feedback on the frequencies and transmission losses? What results would it give me if I went for three or even four layers of drywall on the inside?

Have you tried my calculator? http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21770 I have a few tweaks I need to make to it shortly (one being to add Fermacell)
But more specific to your question, you can add up to 4 layers of material in the calculator.

- Any feedback on the HVAC system? Any concerns with having the fresh air in- and outtake located on the inside of the garage?

Unless I don't fully understand what you're proposing, I don't like it so far. What I'm understanding is that you just want to shoot air in a big circle from one room to another. That won't work. You need fresh air and to expel stale air.

Greg

I just updated the calculator so it has Fermacell in it now:

http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21770

Greg

- Should I leave the window plugs in or remove them before building the room within a room?
You need a complete outer leaf that has great mass so yes, it needs to be plugged. Have considered using brick to plug it?

I did consider that option. However, I expect to live in this house for the next, let's say, +/- 7 years and after that there is a good chance we will look for another home. I would like to have the windows remaining as it would sell better with them.
The current window plugging I've used as the window handle is sticking out. Do you have any comments on the way it's been done? Picture is in the post above.

- Wooden vs steel frame? Any ideas? I’ve read a steel frame is slightly better in reduction. It’s also easier to assemble.
In my opinion, wood. Steel framing is super flimsy and hard to manipulate.

Noted! Transmission losses don't differ that much if you see test results. In your calculation the transmission losses are actually way lower if you select steel studs instead of wooden studs. Is this correct? I recall test data and people mentioning that steel would be slightly better.

- Any feedback on the frequencies and transmission losses? What results would it give me if I went for three or even four layers of drywall on the inside?
Have you tried my calculator? http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21770 I have a few tweaks I need to make to it shortly (one being to add Fermacell)
But more specific to your question, you can add up to 4 layers of material in the calculator.

I actually did try the calculator before. In comparison to some test data it seemed quite optimistic. However, I've tried the 2.05 ones more and it gives me some good direction for the theoretical side. Well put together I must say!
It does leave me with a few questions. Has it been compared to some test data available? What is the accuracy?
These calculations don't take into account any imperfection of course so it is always better to use the formulas in combination with the test data I would assume.

What I would need is some help on figuring out how thick the walls should be. Below is a summary of the calculations I've did for multiple layers for the ceiling, the wall with existing brick wall and the new wall inside the garage which will be a double studded drywall.
I've read a lot that you should design your room so the TL is almost equal on each side as that will be your weakest link. However, this also depends on what you're trying to achieve and who is being disturbed by the noise on which side I would say? Let's say the ceiling will be my limiting factor, would it be a waste of money to isolate the walls facing the existing brick as good as possible to reduce the dB's going to the neighbors?

- Any feedback on the HVAC system? Any concerns with having the fresh air in- and outtake located on the inside of the garage?
Unless I don't fully understand what you're proposing, I don't like it so far. What I'm understanding is that you just want to shoot air in a big circle from one room to another. That won't work. You need fresh air and to expel stale air.

See attached image which I forgot to attach in my first post. I myself also had those concerns. How could I construct it so I will have the silencer boxes on the inside but still getting and bringing air from the outside?

The current window plugging I've used as the window handle is sticking out. Do you have any comments on the way it's been done? Picture is in the post above.

I'd have to see them in more detail but as long as they have mass and are sealed airtight, then you're good to go.

In your calculation the transmission losses are actually way lower if you select steel studs instead of wooden studs. Is this correct? I recall test data and people mentioning that steel would be slightly better.

This is because you must have chosen a smaller steel stud. The calculator does not take the actual material of the studs into consideration. Instead, it adds the depth of the stud to the total distance between the sheathing material. That's why you're seeing the difference.

Has it been compared to some test data available? What is the accuracy?

I didn't create the formulas. They are standard formulas. If you see them as being optimistic that's because the results are based on a perfect construction in a lab. In a real life build there will always be flaws in the construction. You just have to do your best to build with care and hope that you're getting it as close to the predicted results as possible.

However, this also depends on what you're trying to achieve and who is being disturbed by the noise on which side I would say?

To some extent for sure, but most of the rooms being built around the forum are small enough that low frequencies will potentially pollute your neighbors unless all 6 sides of your room are built with intent to contain that energy anyway.

Let's say the ceiling will be my limiting factor, would it be a waste of money to isolate the walls facing the existing brick as good as possible to reduce the dB's going to the neighbors?

The issue with a poorly isolating ceiling is that it is in close proximity to all 4 walls. Also, typically your ceiling is a lot bigger in surface area than a single wall (unless you have a small really tall room!) which means it is leaking a lot more than a poorly built wall would. Furthermore, in a MSM system, the cavity is working as a single entity and with a ceiling like that, it would compromise the entire system.

How could I construct it so I will have the silencer boxes on the inside but still getting and bringing air from the outside?

You can route from an inner to an outer leaf silencer box using easy to use material such as flex duct.

Greg