My DIY sound isolation project - please vet!

[Glenn Kuras]

I would order the book by rod Gervaise. It will answer your questions on build and will save you a lot of headaches in the end

[spliff_enz]

Originally Posted by Glenn Kuras

I would order the book by rod Gervaise. It will answer your questions on build and will save you a lot of headaches in the end

Thank you very much for taking the time to reply!

I actually do own a copy of that book and have already pored over most of it. It did already set right a lot of my pre-existing notions about sound isolation. (the importance of resonance, mass law, decoupling)

The only problem is that my options are somewhat limited - I can't do any invasive construction or modify the existing structure of the building. So to begin with, most of the construction techniques detailed in the book do not serve me too well.

Instead:: What I have done is to take a lot of the principles in the book and attempted it to apply them within the means I can 1) afford 2) legally execute within the terms of my lease agreement (I was alerted to constrained layer damping - GREEN GLUE - through the book, for which I am very grateful.)

What I'm looking for is for someone such as yourself to look at the
1) spatial proposal for my "room within room"
2) choice of materials / proposed techniques
3) any other features of the plans I have detailed, and
hopefully spot any glaring holes in my planning / logic...

And to tell me (ballpark) just how much sound isolation I can expect to achieve through my process.

[jwl]

I'll let others comment on your iso strategy.... I've never built a room that way so I'm not sure how it would perform, I just can't comment.

Regarding the treatment strategy, I definitely would not simply cover all the walls with foam, as you wrote. You want bass trapping in places with bass buildups (ie, corners), and absorption at first reflection points as a practical minimum.

Details here:
RealTraps - Acoustic Basics
RealTraps - Creating a Reflection-Free Zone

[jhbrandt]

Originally Posted by spliff_enz

.........What I'm looking for is for someone such as yourself to look at the
1) spatial proposal for my "room within room"
2) choice of materials / proposed techniques
3) any other features of the plans I have detailed, and
hopefully spot any glaring holes in my planning / logic...

And to tell me (ballpark) just how much sound isolation I can expect to achieve through my process.

Bottom line and in a nutshell, so to speak, sound isolation is accomplished with decoupled mass and air space. That's really IT. I have no idea what you can expect from your construction, but if you were to use the heaviest MASS (decoupled) and at least 5cm (2") of air space, you will obtain the highest STL.
- the big question is: How much Isolation do you REQUIRE??
Please attach your detailed skp file and when I have time, I'll have a closer look.

Cheers,
John

[Tonycamp]

read Rods book again, Insulation in walls? Resilient channel thats pictured is "not" resilient, maybe just the drawing? It looks like your going to be spending plenty of time and $ on this project, you can't learn too much about the process. Better to be over informed than broke in a room where people can hear you crying just outside the walls.

[spliff_enz]

Originally Posted by Tonycamp

read Rods book again, Insulation in walls?

You're right, I didn't have any insulation in the drawings. But I will be having them put in.

Resilient channel thats pictured is "not" resilient, maybe just the drawing?

Absolutely. My sketch is just that, a sketch. I'll be sure to take all precautions when I have the actual installation done.

It looks like your going to be spending plenty of time and $ on this project, you can't learn too much about the process. Better to be over informed than broke in a room where people can hear you crying just outside the walls.

OK, I'll pay attention to your advice.

But like I said, the book doesn't help too much when I can't make any structural changes to the existing room.

[spliff_enz]

Originally Posted by jhbrandt

Bottom line and in a nutshell, so to speak, sound isolation is accomplished with decoupled mass and air space. That's really IT. I have no idea what you can expect from your construction, but if you were to use the heaviest MASS (decoupled) and at least 5cm (2") of air space, you will obtain the highest STL.
- the big question is: How much Isolation do you REQUIRE??
Please attach your detailed skp file and when I have time, I'll have a closer look.

Cheers,
John

Wow, okay! I will fill in more details into the skp file and have it uploaded. Thank you very much again!

[Tonycamp]

Originally Posted by spliff_enz

But like I said, the book doesn't help too much when I can't make any structural changes to the existing room.

Wrong

You can do a tremendous amount of improvement with just about any existing structure

[spliff_enz]

Originally Posted by jhbrandt

Bottom line and in a nutshell, so to speak, sound isolation is accomplished with decoupled mass and air space. That's really IT. I have no idea what you can expect from your construction, but if you were to use the heaviest MASS (decoupled) and at least 5cm (2") of air space, you will obtain the highest STL.
- the big question is: How much Isolation do you REQUIRE??
Please attach your detailed skp file and when I have time, I'll have a closer look.

Cheers,
John

Hi John,

I've revised my drawing to a great degree, putting a lot more detail into it; in the process, also changing the boundaries of my "room within room".

a) The file is Sidd's Room REV4.skp. I hope you can look at it when you have a little time and give me your valuable opinion especially with regards to how much isolation I can hope to achieve from it.

b) There is a concrete loft existing in this room. I have shown it to scale in the drawing and factored my isolation under and around it. Given its dimensions (561 mm deep + about 1990mm and up above the floor + along almost the whole length), do you think the little expose region can still be a problem for the room response?

c) Please also tell me if you have any idea about this 'Acoustud' brand of "vertical" resilient channels from SAINT-GOBAIN - it's on the market here and though there's not much information online (I have attached the catalogue here WB09_GypWall_RAPID_dB_Plus_07.pdf), I am made to believe that it is fairly effective. What's your take?

Thank you very much for your help. I will hugely appreciate it.

--------

Additional details (these are shown in the drawing but I have tried to explain them in text here):

ISOLATION
Following the "two-leaf" system, this is what I have planned to build to achieve maximum isolation:

(from out-to-in)
1) WALLS:
MASS(Existing concrete wall+Softboard panels+1 layer of 5/8" or 15mm drywall) + AIR (in the form of 70mm wide hollow vertical channel - 'Acoustud' brand from Saint-Gobain, installed on the frame with 450mm centres) with some soft fiberglass wool and finally - MASS again (2nd layer of 15mm Drywall+ 3rd layer with GREEN GLUE applied before installation)

2) FLOOR (I have neighbours on the floors above as well as below):
The existing floor is tiled - which I cannot change; so what I have planned is to install a 3PLY 4mm thick PLYWOOD on top of it with GREEN GLUE (Constrained Layer Damping technique); and then put my carpet on it.

3) CEILING:
Acoustud vertical channel across the ceiling with a single layer of drywall fixed to it. 2nd layer with GREEN GLUE will be consider if necessary but suspension strength may come into question.

Others: The existing window to the room will be fully boarded up. Existing doors will also be reinforced with techniques I learned from Rod's book.

TREATMENT
The inner dimensions of my room are going to be (in mm):
3720 (L) X 2745 (W) X 2077 (H)

This ratio is roughly 1 : 1.4 : 1.90 (MM Louden's first); and after using your MODECALCULATOR(metric), I have figured that I may have some lone frequency around 60 Hz that may need attention.

For 'Room treatment', I intend to do 2 things
1) I will build high-frequency broadband absorption panels using what I learnt from Rod Gervais' book

2) I will build "superchunk bass traps" (broadband) stacked at the corners of the room, using what I've learnt from here.

[spliff_enz]

*bump* :-/

[spliff_enz]

SOMEONE.. please..

[jhbrandt]

I had a good look at your sketchup file and noting that you are on the upper floor of a concrete/brick apartment building.

OK. First you probably already have about STC50 between you and the neighbors. Impact transmission will lower this rating.

It would be very difficult to improve of the low frequency transmission loss without heavier partitions and larger air gaps. ESPECIALLY the floor!

This is a case where, if you need more transmission loss - especially at low frequencies, you will need to have a proper floating floor. -- which means at least a 5cm air gap and at least 5cm of reinforced concrete pour.

Anything less than that will actually decrease your isolation. Read my new paper "How to find out how much Isolation you need" found under Articles on my publications page.

I would recommend that you only treat your room with acoustic treatment and add impact isolation flooring to the floor. This can be done with 4-6mm of Regupol, a recycled rubber product.
-- But find out exactly what you need and what frequency range you need it in before you go spending loads of money and weeks of time. I recommend at least some testing to find out where you are now in relation to how loud you will be able to play/perform and what instruments will be restricted.

Adding light mass to the walls will only raise the resonance dip and actually make transmission worse, especially in the low frequencies. - Right where you need it.

This is not an easy situation and compromise is necessary. But by compromise, i don't mean building something that won't work - I mean work within the structure of what you have and don't try to change something that you cannot. You can change what you do and the times that you do it.

Cheers,
John

[spliff_enz]

Originally Posted by jhbrandt

I had a good look at your sketchup file and noting that you are on the upper floor of a concrete/brick apartment building.

OK. First you probably already have about STC50 between you and the neighbors. Impact transmission will lower this rating.

It would be very difficult to improve of the low frequency transmission loss without heavier partitions and larger air gaps. ESPECIALLY the floor!

This is a case where, if you need more transmission loss - especially at low frequencies, you will need to have a proper floating floor. -- which means at least a 5cm air gap and at least 5cm of reinforced concrete pour.

Anything less than that will actually decrease your isolation. Read my new paper "How to find out how much Isolation you need" found under Articles on my publications page.

I would recommend that you only treat your room with acoustic treatment and add impact isolation flooring to the floor. This can be done with 4-6mm of Regupol, a recycled rubber product.
-- But find out exactly what you need and what frequency range you need it in before you go spending loads of money and weeks of time. I recommend at least some testing to find out where you are now in relation to how loud you will be able to play/perform and what instruments will be restricted.

Adding light mass to the walls will only raise the resonance dip and actually make transmission worse, especially in the low frequencies. - Right where you need it.

This is not an easy situation and compromise is necessary. But by compromise, i don't mean building something that won't work - I mean work within the structure of what you have and don't try to change something that you cannot. You can change what you do and the times that you do it.

Cheers,
John

Thank you so much for weighing in, John. Good lord! Am I really glad I checked on this board!

Sound isolation is such a complex field - I mean that there are so many counterintuitive ideas.. Decoupling vs Mass-air-mass resonance... Constrained-layer-damping (a la Green Glue) vs inadequate stiffness to be effective.. Concrete as good isolation vs bad for reflections within .. I've spend the best part of the last month studying threads on this forum; but I just knew I had to get my plans vetted before I put any money down, in case some aspect of my design backfired later. And voila! I was right! About being wrong!

I'm going to take your advice. I strained to understand it at first but after 3-4 hours of looking up more theory and similar threads on the forum I think I finally did.. i.e. i) adding insufficient mass to the walls of a concrete structure might only serve to worsen the direct sound transmission by providing an 'easier' intermittent medium.. ii) creating a decoupled resilient-layer partition with thin air gap (7 cm) and relatively less mass as according to my plans might only worsen things below the 'resonant frequency' and by facilitating resonance at a higher LF point than otherwise.. iii) therefore, Green Glue might not work in my case without a resilient partition, and in the absence of layers with sufficiently close stiffness - I'm glad I didn't waste money on this too.. (did I get all this right?? )

Broadly speaking, I've revised my plans to the following (in order):

1) Fix my 'weakest links' - seal the window and reinforce the doors (either professionally or DIY by adding a layer of MDF/particleboard to the existing door to first make it heavier and then adding commercial rubber-based side/BOTTOM-sealers around the whole thing, sealing all air gaps (and hopefully pressure sealing the inside when mechanically closing the door).

2) TEST: Get the room's existing isolation properties tested at various frequencies, from.. downstairs.. upstairs.. nearby rooms..

3) TEST: Get the room's UNTREATED frequency response measured and calculated within the room.

4) Using information from the isolation TEST (point 2) to plan exactly how I can :
a) possibly strengthen the 'weakest link', say any one wall or two adjacent walls that I find to be worse at transmission
b) lowering impact-noise-transmission especially through the floor. I may have to go for Regupol's 3912 product - 6 mm - to fix directly on my tile floor and then carpet over it.

5) Using information from the frequency response TEST (point 3) to plan exactly:
a) how many / what bass traps I might need to build, and
b) how many / what broadband attenuators I might need to build
to get a 'decently' flat response from the room.

6) Finally testing the 'treated' room's frequency responses again and fixing any anomalous modes (esp LF) by building membrane absorbers to target the specific frequency.

I think I've grasped this to a certain measure.. (have I??)

I will be posting updates on the forum. I'll try to keep them as specific as possible. I hope you folks will continue to support me.

Once again.. thanks, John. You may have literally saved me hundreds of dollars worth of materials, hundreds of hours of work and a lot of heartache! You really know your art, sir! Thanks to everyone else too.

Cheers to Gearslutz. What a fantastic way to learn..

Thank you so much again.