John Sayers' Recording Studio Design Forum Archive

* * * *

Hi Tony, and Welcome!

Great first post, by the way!

So let's start with your last question fist:

4. Am I completely deluded and need to be spanked back into reality?

Yup! For sure! I mean, here you are along with the rest of us nuts who share the same brand of insanity, by wanting to build a full-blow studio inside a house! So yep, you are fully qualified along with all of the other forum members, as a suitably deluded studio builder.

All outside walls are 300m solid brick with thick cement render,

Great! That's a good start.

and internals are at least 160mm.

Also brick?

The room I am intending to use is the downstairs front room.

What's under that: basement? mother earth? crawl space?

Floors are heavy timber joist with floor boards, then carpet.

First order of business: lose the carpet, and get a structural engineer in to tell you (in writing) how much extra load you can place on those joists. You'll be adding man hundred of kg of extra load on those, so you need to know if you can do that safely and legally.

The Ceiling is plasterboard, which then turns into the upstairs front room with is timber floor, carpet.

Ditto: Engineer. Loads. You might need to "beef up" that ceiling with extra mass, so you need to know how much extra you can safely hang from the joists.

transmission from room to room is low.

How low? How many dB TL are you getting right now, with the existing structure? Both between rooms, and also from inside to outside. That needs to be measured with a proper hand-held sound level meter.

long form cinema release's of classical music, opera and ballet, so deep sub-bass synth lines are not going to be expected

Ummmmm... I'm not so sure about that. There are many instruments in a typical orchestra that put out a lot of energy in low frequencies. A grand piano goes down to 27.5 Hz, cello down to 65, double-bass down to 40, bassoon 58, contrabasoon 29, bass trombone 61, harp 31... All of that is way down in the part of the spectrum that is hard to isolate.

I am hoping to get as much sound isolation as is possible within my budget,

Numbers! Need to put that in real-world decibels. You can plug decibel nu,bers into equations, and loo them up on graphs and tables, but you can't plug in the phrase "as much as possible" to an equation...

My monitoring is three ATC SCM 25A's with two Neumann KH120's and a matched ATC Sub for LFE which is not a monster system,

It's fine for what you want. More than fine, in fact.

As my clients are often an arts organisation, client previews is important so the fit and finish is an important aspect as is a sense of space as there can be a few of them.

My first suggestion would be to forget about trying to have two people mixing at once, side by side, and rather have just the engineer seated in the center of the sweet spot, with a client couch set up further back. towards the rear of the room.

All noise makers will be housed in racks outside the mix room in an adjacent room.

Do take careful not of what you need to do to isolate that cable run! You'll have a snake that needs to get through, and it will be large...

Note: this is just a mockup using models of quadratic residual diffusers I have made in the past for other projects. The intention was to see whether would be enough space to work in.

There isn't! Sorry. The room is not beig enough to be able to use numeric-sequence diffusion, and least of all on the walls. According to D'Antonio and Cox, you need at least 10 feet (3m) between any such diffuser and your ears, so that there is enough space for the lobing, phasing, and scattering artifacts to smooth out. Your room dimensions are not large enough to do that. In addition 10feet is the minimum: the distance might need to be even greater, depending on the tuning of the diffuser: you need at least 3 full wavelengths of the lowest cut-off frequency.

For your room, realistically, numeric-based diffusers are out.

Yes, you often do see small home studios with diffusers on the walls, but that's just a display of acoustic ignorance. You cannot get smooth, accurate, well-spread coverage like that. Just because you see it in photos, does not make it acoustically correct, in the same way as egg-crates on the walls, carpet on the ceiling, and monitors on the meter bridge... often seen, never correct.

Based on my previous experiences of building large studios, I have done some conceptual drawings

Yep, there's the problem! Your experience is in large studios, where there is enough space to do what you show in the model. But small rooms do not behave the same way as large rooms do, acoustically, and the type of treatment that can be used is different.

My feeling is that I will need to build a single leaf room

You already have a single leaf room! Anything you do inside of that is going to make it at least two leaves...

Yeah, I get it , but I love to be pedantic! What you plan to do is to build an additional leaf inside the existing leaf, thus creating your 2-leaf MSM system.

on an isolated "floating" floor

Ummmm... Nope! Bad idea. Here's why: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

on top of the old carpet in the room,

Another bade idea: the carpet has to go. You can't build anything on top of carpet. It would be impossible to get an air-tight seal like that, and it would be unsafe anyway. Probably not even permitted by code.

The carpet will have to go, regardless of what you end up doing for the floor.

The current room has windows, but I will not add this to my new studio to save costs.

How do you plan to seal up that existing window? If it is an operable window, then it will need to be completely sealed, and likely the glass will need to be replaced with somthing thicker. The concept of 2-leaf MSM isolation is that the surface density of each leaf must be consistent throughout, or at the very least, the weakest area must still have e3nough surface density to produce the required tuning with a reasonable sized air gap. Having a large area of thin window glass would make it very hard to do that.

The current door will need to be removed, and I am considering adding a new door to the outside of the room in the hallway to act as a second closure to the heavy studio door to be added onto the inner sealed room.

You seem to be missing the point of how 2-lewaf isolation works: have a door in each leaf is not something that you can "consider": it is absolutely necessary! If you only have a door in one leaf, then you might as well not build the other leaf at all! You'd have no isolation. You need one door in each leaf, and each of the doors needs to have the right surface density for the leaf it is in. If the outer-leaf is the higher density (more massive) leaf, then that one needs the heavier door.

Past builds have made me really like Steel Framing (Rondo in Australia), for its easy reusability and construction.

That's fine. There's actually a small advantage from steel framing, for isolation.

I am wondering if I can use 19mm particleboard usually used for flooring instead of plasterboard

You got me there! why were you even considering using plasterboard for flooring??? Are you talking about using it to beef up the mass of the floor, as in an in internal layer between other layers? You could do that, but I'd never consider using plasterboard as the only flooring! Maybe you could explain this a but more?

So, the intended construction of the studio walls would be neoprene flooring,

Why? Why would you want to have "neoprene flooring" under your walls? There's no benefit from that, unless you do all the math to carefully calculate the correct loading that you'd need in order to actually make the wall and ceiling "float". It won't happen by accident. You need to do the math. This is the the exact same issue as in that link above, about floating your floor. Same issues, same problem.

Centre of the room will have a timber floor, and the outside will have carpet.

Take a look at photos of world-class studios: how many do you see with carpeted floors? Somewhere down around zero. There's a reason for that? carpet messes up the acoustics of a studio. It does the exact opposite of what small rooms need. It absorbs highs really, really well, mids sort-of-but-un-predictably, and lows not at all. Small rooms need the reverse: Major absorption in the lows, controlled accurate absorption in the mids, and practically nothing in the highs. carpeting your floor is a recipe for shooting yourself in the foot, acoustically.

The walls and ceiling would similarly be steel frame, insulated with appropriate batts, and then three layers of particle board.

Do you really need that much isolation? You are describing the type of wall that I'd normally use for a drum booth, or a live room for a rock band. You won't be doing any live tracking at all, so I don't see the need for such high levels of isolation. How much isolation do you need (in decibels)?

I am wondering if there is some way to decrease transmission either by using different thicknesses of board,

You can, yes, but the slight benefits you get by varying the density/thickness of the layers is outweighed by eh benefit you would have gotten by just making all layers of the highest density stuff. It's the low end that matters most in isolation, and what governs that part of the spectrum is MSM resonance. The key to that is mass. Lots of mass. The benefits you'd get from varying thickness/density are much higher up the scale, roughly around the coincidence dip, which normally isn't a problem for a well designed MSM wall anyway.

or adding some rubber joint or something.

Nope. And if you think GG is expensive, try quoting for enough surface area of rubber to cover all your wall and ceiling surfaces!!!

Just go with rigid mass.

The room has quite thick cornicing and door / window frames, as well as a large fireplace,

Those will end up inside the MSM cavity, I assume? Also, what is your plan for sealing up the fireplace? I'm assuming it is functional, and has a chimney that exits to the outside world: that will have to be bricked up and sealed off. You cannot have any penetrations of either leaf.

Calculating the wall thickness at 75mm Frame, 3x 20mm board is 135mm, so I will allow 150mm.

Are you sure that's enough to get your MSM resonance down low enough? Did you do the math?

1. Given the size of the room, is there merit in modifying the walls to add 7 degree splays to decrease standing waves,

Myth. Splaying your walls does not "decrease standing waves". It merely moves them to a different frequency. And 7° is not enough to do much of that anyway. Room modes (standing waves) are basically paths that a sound wave can take around he room and get back to where it started while still being in phase with itself. They are due solely and completely to the room dimensions. Axial modes involved two walls that are on opposite sides of the room, roughly parallel to each other. tangential modes involve any four walls (where I'm counting the ceiling and floor as "walls" as well). Oblique modes involve all six walls. Angling walls might reduce the number of direct axial modes, but it will increase the number of tangential and/or oblique modes. That's all. You cannot get rid of modes by angling walls. You might be able to re-arrange them usefully, but they'll still be there.

The reason why you might want to angle parts of your walls, is if you decide to go with a room design philosophy that calls for that, such as RFZ for example, which would be very much recommendable. but if you just want a "plain vanilla" rectangular room (without the benefits of those design philosophies) then there's no point to splaying walls.

or would these be better handled by treatment.

It's a small room: it will need a lot of treatment anyway! That goes without saying. Angling the walls unnecessarily would reduce that space even further....

On the other hand, angling parts of some walls intelligently could, indeed, produce vary useful benefits, of done correctly. But it would not be the entire walls: just small sections of the front and side walls, so the lost space is minimal, and the benefits outweigh the losses.

Is the loss of internal space, important for ergonomics and for acoustic air volume, outweighed by the reduction in modes?

No, because there won't be any reduction in modes! and in fact, reducing the number of modes is a bad thing, not a good thing! Especially in the low end. You WANT modes down there, as many as possible, spaced as closely and as evenly as you can get them. That's the entire point to choosing a good room ratio: having modes that are evenly spaced, so the gaps between the modes are small. If it were possible to get rid of some modes, that would mean that there would be fewer modes to spread around! the modal response would be even more uneven. That would make the room worse, not better.

But fortunately, it isn't possible to "get rid" of modes. They are a fact of life, and you are stuck with them, so you just have to make the most of them. That's what bass trapping is for: to damp the modes, evenly and smoothly.

2. Is my idea of using Yellow-Tongue particleboard ridiculous or is it a good idea for reuse later if and when I have to move?

Isolation is mostly about low frequencies, since those are the toughest to isolate. Low frequency isolation depends mostly on MSM resonance. MSM resonance in turn depends mostly on two factors: mass, and air gap. The more mass you can put on each leaf the lower goes the MSM resonance. The larger you can make the air gap, the lower goes the MSM resonance. So your goal is to have as much mass (density) as you can get in each leaf, and as large an air gap between them as you can afford. As long as your mass is air-tight and high enough density to do the job, it doesn't really mater what you use: platerboard, MDF, plywood, OSB, glass, brick, concrete, fiber-cement board, steel plate, lead sheet... as long as the surface density and the cavity depth are correctly chosen to get the MSM resonance down low enough, then you are fine.

So just do the math, and see if your proposed materials will do the job.

3. Is the there some construction method with the framing, insulation and boards that could maximise the resistance to transmission?

Yep! "Fully-decoupled two-leaf MSM isolation". That's they method that provides the highest overall isolation for the lowest cost, in the least space. All other systems either require more space, more mass, or more money.

To be worked on...
Doors, HVAC, Services and Acoustic treatment

Before you can settle on the final dimensions of the room, you need to do all your HVAC design: silencer boxes are large, and take up a lot of space. You need to account for that when deciding on room dimensions...

- Stuart -

Soundman2020 wrote:Great first post, by the way!

Thanks - after a lot of reading here I knew that the first post needed to be well formed if was to elicit a response from Chile! I am quite floored with how much you post and in such detail. My intention in posting was not to seek easy answers, but to help me refine my questions, to assist my next phase of research. Your generous response has been wonderfully helpful.

and internals are at least 160mm.

Also brick?

A: Yes, solid brick with render. These Terraces feel very dense, with almost no sound coming through neighbouring walls.

The room I am intending to use is the downstairs front room.

What's under that: basement? mother earth? crawl space?

A: The property is built on level ground, with the walls on ground level and the ground floors raised on approximately 400mm high brick foundations. The Joists and flooring from what I have seen are heavier than what I see in newer constructions.

Floors are heavy timber joist with floor boards, then carpet.

First order of business: lose the carpet, and get a structural engineer in to tell you (in writing) how much extra load you can place on those joists. You'll be adding man hundred of kg of extra load on those, so you need to know if you can do that safely and legally.

A: I hear you. However, losing the carpet is not an option for this iteration of my production studio. Part of the agreement was to not impact the existing conditions. I have engaged an engineer, and initial discussions are positive with the additional 1500kilos this build is likely to add.

The Ceiling is plasterboard, which then turns into the upstairs front room with is timber floor, carpet.

Ditto: Engineer. Loads. You might need to "beef up" that ceiling with extra mass, so you need to know how much extra you can safely hang from the joists.

A: The existing ceiling shall also remain untouched. My intention was to build a ceiling, supported by in the inner leaf's walls.

transmission from room to room is low.

How low? How many dB TL are you getting right now, with the existing structure? Both between rooms, and also from inside to outside. That needs to be measured with a proper hand-held sound level meter.

A: I am a professional working audio engineer, and am use FuzzMeasure and calibrated test mics almost daily. What process is suggested to correctly assess the TL. I suspect that I can take some impulse response sine sweeps within the room, and then from various points outside and upstairs from the room to then see what differences there are. How does one then arrive at a single value? As the TL would differ significantly across the spectrum.

long form cinema release's of classical music, opera and ballet, so deep sub-bass synth lines are not going to be expected

Ummmmm... I'm not so sure about that. There are many instruments in a typical orchestra that put out a lot of energy in low frequencies. A grand piano goes down to 27.5 Hz, cello down to 65, double-bass down to 40, bassoon 58, contrabasoon 29, bass trombone 61, harp 31... All of that is way down in the part of the spectrum that is hard to isolate.

A: Ha! I actually had a feeling you would be this pedantic I was of course referring to the difference of a late night EDM Mix Session with pure sine wave 35Hz bass synth drops versus Shostakovich's 10th Allegro. Somehow one permeates a little more

I am hoping to get as much sound isolation as is possible within my budget,

Numbers! Need to put that in real-world decibels. You can plug decibel nu,bers into equations, and loo them up on graphs and tables, but you can't plug in the phrase "as much as possible" to an equation...

A: Fair enough point. And the lack of a number from me was due to lack of facts. I will do some testing tomorrow and come back with a better notion of what a figure. From a usage perspective, If I am able to mix into the night and not disturb my neighbours whilst mixing at 78dBC I will be very very pleased.

My monitoring is three ATC SCM 25A's with two Neumann KH120's and a matched ATC Sub for LFE which is not a monster system,

It's fine for what you want. More than fine, in fact.

A: Yes, I am very pleased with its performance. The smaller cabinets lack high SPL grunt, but actually have a more refined top end. Luckily i have been responsible with my ears so can still hear past 2k.

As my clients are often an arts organisation, client previews is important so the fit and finish is an important aspect as is a sense of space as there can be a few of them.

My first suggestion would be to forget about trying to have two people mixing at once, side by side, and rather have just the engineer seated in the center of the sweet spot, with a client couch set up further back. towards the rear of the room.

A: I may have misled. I never have two people mixing, despite what my little model suggests. Client will always sit at the sweet spot whilst i operate the preview playback.

All noise makers will be housed in racks outside the mix room in an adjacent room.

Do take careful not of what you need to do to isolate that cable run! You'll have a snake that needs to get through, and it will be large...

A: Am well across the services aspect - been there many times, and thankfully technology only makes this easier for us. Thunderbolt and UHD-HDMI not included...

Note: this is just a mockup using models of quadratic residual diffusers I have made in the past for other projects. The intention was to see whether would be enough space to work in.

There isn't! Sorry. The room is not big enough to be able to use numeric-sequence diffusion, and least of all on the walls. According to D'Antonio and Cox, you need at least 10 feet (3m) between any such diffuser and your ears, so that there is enough space for the lobing, phasing, and scattering artifacts to smooth out. Your room dimensions are not large enough to do that. In addition 10 feet is the minimum: the distance might need to be even greater, depending on the tuning of the diffuser: you need at least 3 full wavelengths of the lowest cut-off frequency.

For your room, realistically, numeric-based diffusers are out.

A: This is a perfect example of what I had hoped to glean. Thanks. Now that you point it out, it is quite obvious really. Shame, as I love the look of a QRD.

Based on my previous experiences of building large studios, I have done some conceptual drawings

Yep, there's the problem! Your experience is in large studios, where there is enough space to do what you show in the model. But small rooms do not behave the same way as large rooms do, acoustically, and the type of treatment that can be used is different.

A: Guilty as charged.

My feeling is that I will need to build a single leaf room

You already have a single leaf room! Anything you do inside of that is going to make it at least two leaves...

Yeah, I get it , but I love to be pedantic! What you plan to do is to build an additional leaf inside the existing leaf, thus creating your 2-leaf MSM system.

A: Yes!

on an isolated "floating" floor

Ummmm... Nope! Bad idea. Here's why: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

A: Thanks for the link, I spent a good few hours on there and can understand the reasoning.

on top of the old carpet in the room,

Another bade idea: the carpet has to go. You can't build anything on top of carpet. It would be impossible to get an air-tight seal like that, and it would be unsafe anyway. Probably not even permitted by code. The carpet will have to go, regardless of what you end up doing for the floor.

A: Hmm. Sounds like this will be an issue, as I am unable to remove the carpet. More thinking required.

The current room has windows, but I will not add this to my new studio to save costs.

How do you plan to seal up that existing window? If it is an operable window, then it will need to be completely sealed, and likely the glass will need to be replaced with somthing thicker. The concept of 2-leaf MSM isolation is that the surface density of each leaf must be consistent throughout, or at the very least, the weakest area must still have enough surface density to produce the required tuning with a reasonable sized air gap. Having a large area of thin window glass would make it very hard to do that.

A: I was planning to build a frame around the existing window frame on the inside, that has a layer or two of board to provide a greater density at those apertures.?

The current door will need to be removed, and I am considering adding a new door to the outside of the room in the hallway to act as a second closure to the heavy studio door to be added onto the inner sealed room.

You seem to be missing the point of how 2-lewaf isolation works: have a door in each leaf is not something that you can "consider": it is absolutely necessary! If you only have a door in one leaf, then you might as well not build the other leaf at all! You'd have no isolation. You need one door in each leaf, and each of the doors needs to have the right surface density for the leaf it is in. If the outer-leaf is the higher density (more massive) leaf, then that one needs the heavier door.

A: Thanks for the clarification. My consideration was more to do with the HOW as opposed to the IF

Past builds have made me really like Steel Framing (Rondo in Australia), for its easy reusability and construction.

That's fine. There's actually a small advantage from steel framing, for isolation.

A: Great.

I am wondering if I can use 19mm particleboard usually used for flooring instead of plasterboard

You got me there! why were you even considering using plasterboard for flooring??? Are you talking about using it to beef up the mass of the floor, as in an internal layer between other layers? You could do that, but I'd never consider using plasterboard as the only flooring! Maybe you could explain this a but more?

A: My sleepiness may have confused. My question was whether using Particleboard for the walls would be feasible. The boards in question are common flooring boards. I am trying to avoid Plasterboard as its a mess to pull apart and not easily reusable.

So, the intended construction of the studio walls would be neoprene flooring,

Why? Why would you want to have "neoprene flooring" under your walls? There's no benefit from that, unless you do all the math to carefully calculate the correct loading that you'd need in order to actually make the wall and ceiling "float". It won't happen by accident. You need to do the math. This is the the exact same issue as in that link above, about floating your floor. Same issues, same problem.

A: Thanks for the reiteration. The "Math" is a hard one as its difficult to know where to start, and I feel that to do so would be foolish without additional study.

Centre of the room will have a timber floor, and the outside will have carpet.

Take a look at photos of world-class studios: how many do you see with carpeted floors? Somewhere down around zero. There's a reason for that? carpet messes up the acoustics of a studio. It does the exact opposite of what small rooms need. It absorbs highs really, really well, mids sort-of-but-un-predictably, and lows not at all. Small roms need the reverse: Major absorption in the lows, controlled accurate absorption in the mids, and practically nothing in the highs. carpeting your floor is a recipe for shooting yourself in the foot, acoustically.

A: I hear you. The intention was to save money by only carpeting 50percent of the floor, usually covering the operating area of the room. I have done this before on other control rooms successfully, but as you have pointed out they were far bigger. And, I had employed qualified respected acoustic guru's.

The walls and ceiling would similarly be steel frame, insulated with appropriate batts, and then three layers of particle board.

Do you really need that much isolation? You are describing the type of wall that I'd normally use for a drum booth, or a live room for a rock band. You won't be doing any live tracking at all, so I don't see the need for such high levels of isolation. How much isolation do you need (in decibels)?

A: I think is is emerging as a central question, and one that I am going to have to do some testing on tomorrow. Right now, its 1am in Sydney, and the loudest noise I can hear is my Fridge and analogue wall clock as I sit in the kitchen. Using my two trusted tools, one a decent iPhone app, and the other the a Calibrated BeyerDynamic MM1 with SMART running on my laptop, I can see that the current ambient noise floor hovers around 33dBC SPL when I am still, and 45dBC when typing.

So, If I was to be mixing in my room at an average of 78dBC, momentary peaks of 86dBC, then for silence here in the kitchen I would want to have around 50dB of TL if I didn't want to be a nuisance.

Am I dreaming I suspect so.

I am wondering if there is some way to decrease transmission either by using different thicknesses of board,

You can, yes, but the slight benefits you get by varying the density/thickness of the layers is outweighed by the benefit you would have gotten by just making all layers of the highest density stuff. It's the low end that matters most in isolation, and what governs that part of the spectrum is MSM resonance. The key to that is mass. Lots of mass. The benefits you'd get from varying thickness/density are much higher up the scale, roughly around the coincidence dip, which normally isn't a problem for a well designed MSM wall anyway.

A: Great - another popular misconception clarified for me. Thanks.

or adding some rubber joint or something.

Nope. And if you think GG is expensive, try quoting for enough surface area of rubber to cover all your wall and ceiling surfaces!!! Just go with rigid mass.

A: Done.

The room has quite thick cornicing and door / window frames, as well as a large fireplace,

Those will end up inside the MSM cavity, I assume? Also, what is your plan for sealing up the fireplace? I'm assuming it is functional, and has a chimney that exits to the outside world: that will have to be bricked up and sealed off. You cannot have any penetrations of either leaf.

A: Right. So, in additional to the two leafs (Masses) being airtight, the air gap (Spring) itslef needs to be sealed to provide compressive resistance to the two masses. Is that right?

Calculating the wall thickness at 75mm Frame, 3x 20mm board is 135mm, so I will allow 150mm.

Are you sure that's enough to get your MSM resonance down low enough? Did you do the math?

A: Ha! No. I will do some research into MSM Resonance and see what I can learn.

1. Given the size of the room, is there merit in modifying the walls to add 7 degree splays to decrease standing waves,

Myth. Splaying your walls does not "decrease standing waves". It merely moves them to a different frequency. And 7° is not enough to do much of that anyway. Room modes (standing waves) are basically paths that a sound wave can take around he room and get back to where it started while still being in phase with itself. They are due solely and completely to the room dimensions. Axial modes involved two walls that are on opposite sides of the room, roughly parallel to each other. tangential modes involve any four walls (where I'm counting the ceiling and floor as "walls" as well). Oblique modes involve all six walls. Angling walls might reduce the number of direct axial modes, but it will increase the number of tangential and/or oblique modes. That's all. You cannot get rid of modes by angling walls. You might be able to re-arrange them usefully, but they'll still be there.

The reason why you might want to angle parts of your walls, is if you decide to go with a room design philosophy that calls for that, such as RFZ for example, which would be very much recommendable. but if you just want a "plain vanilla" rectangular room (without the benefits of those design philosophies) then there's no point to splaying walls.

A: Thanks for explaining it like that - makes sense when described in that manner. I will read up further on the RFZ approach, and see how this may be a direction for me to pursue.

or would these be better handled by treatment.

It's a small room: it will need a lot of treatment anyway! That goes without saying. Angling the walls unnecessarily would reduce that space even further....

On the other hand, angling parts of some walls intelligently could, indeed, produce vary useful benefits, of done correctly. But it would not be the entire walls: just small sections of the front and side walls, so the lost space is minimal, and the benefits outweigh the losses.

A: Interesting. I had toyed with some shapes that divided the walls into smaller sections that were angled to avoid standing waves. this was done just as an exercise in visual and first principle sound wave behaviour. Would you be able to recommend some reading - or a google search string? Often knowing the right question is the hardest step.

2. Is my idea of using Yellow-Tongue particleboard ridiculous or is it a good idea for reuse later if and when I have to move?

Isolation is mostly about low frequencies, since those are the toughest to isolate. Low frequency isolation depends mostly on MSM resonance. MSM resonance in turn depends mostly on two factors: mass, and air gap. The more mass you can put on each leaf the lower goes the MSM resonance. The larger you can make the air gap, the lower goes the MSM resonance. So your goal is to have as much mass (density) as you can get in each leaf, and as large an air gap between them as you can afford. As long as your mass is air-tight and high enough density to do the job, it doesn't really mater what you use: platerboard, MDF, plywood, OSB, glass, brick, concrete, fiber-cement board, steel plate, lead sheet... as long as the surface density and the cavity depth are correctly chosen to get the MSM resonance down low enough, then you are fine.

So just do the math, and see if your proposed materials will do the job.

A: Thats good to hear as that's intuitive and aligns with my current plans. How would I search to find the methods to do the math on this Stuart?

To be worked on...
Doors, HVAC, Services and Acoustic treatment

Before you can settle on the final dimensions of the room, you need to do all your HVAC design: silencer boxes are large, and take up a lot of space. You need to account for that when deciding on room dimensions...

A: Yes, I have plans for this that do not impinge on the foot print of the discussed space - later posts will no doubt be made to gather input.

Thank you for your kind assistance and generous sharing of your knowledge Stuart. Sincerely appreciated.

Tony

* * * * *

I fixed your reply, by "nesting" the quotes inside other quotes, to make it clearer who is where...

with the walls on ground level and the ground floors raised on approximately 400mm high brick foundations.

OK, so is there just empty air under the floor, between the joists? Do you have access down there? Photo? The reason I ask is that you might need to put some porous absorption in there to damp any strange resonance that might be happening, and messing up wither your isolation or your room acoustics... or both!

However, losing the carpet is not an option for this iteration of my production studio. Part of the agreement was to not impact the existing conditions. I have engaged an engineer, and initial discussions are positive with the additional 1500kilos this build is likely to add.

Ummm.. don't look know, but stacking 1500 kg of building materials on top of a carpet, concentrated in a linera load that is just 3.5 inches wide... well, that's going top mash the carpet to pieces! After you take that out, I hardly think that the carpet will still be "in the existing condition"... It will be mince-meat. Never again usable as carpet.

Here's what you'll need to do: reach an agreement with the owner/landlord that you will replace the carpet with something similar or better when you leave. Better still: buy the carpet now, and hand it over to him as your gesture of "good-faith", and agree that you'll pay the installation costs when you leave. Alternative 2: get a quote for doing that now, and write a cheque to cover those costs, which you then leave with a public notary to be cashed at the tome you leave. Or write it into the rental contract. Or...

There a are reasonable ways of dealing with issues like this. A reasonable owner/landlord would jump at the chance of having brand new carpeting installed, for free, after you leave! It's a small extra cost for you now, and will avoid a major issue when you leave.

A: The existing ceiling shall also remain untouched. My intention was to build a ceiling, supported by in the inner leaf's walls.

Right, but that will potentially create a 3-leaf system.... read up on that...

You could do the same here: agree that you will return the existing ceiling to current condition at the time you leave, and provide a security deposit to cover the cost of doing that in the event you skip town...

A: I am a professional working audio engineer, and am use FuzzMeasure and calibrated test mics almost daily.

... and how do you calibrate all that? Some place in all of your gear you must have an accurate hand-held sound level meter. That's your starting point. You can't use an iPhone app to get accurate sound level reason, for one simple reason: the mic on your iPhone is not an acoustic measurement mic! It's isn't even omni-directional, and it certainly does not have dead flat liner response across the entire audio spectrum. You can get acoustic measurement mics for cell phones (I have one), but in reality you still need a proper hand-held sound level meter, that is hopefully well calibrated. That's what you use to calibrate everything else. You need to tell FuzzMeasure that the level it thinks is 94 dBC in reality is only 87 dBC. Or 98 dBC. Or whatever it turns out to be. If not, then it has no way of knowing. Even if you use a calibrated USB mic, you still need to check that against reality, so a hand-held meter is the basis for everything you do. If you don't have one, then you need to get one. Get a good one: Extech, Galaxy, or some such (B&K if you have big bucks laying around!). Do not get cheap Chinese junk toys. A good one will cost you around US$ 100 or so. Well worth it.

What process is suggested to correctly assess the TL. I suspect that I can take some impulse response sine sweeps within the room, and then from various points outside and upstairs from the room to then see what differences there are. How does one then arrive at a single value? As the TL would differ significantly across the spectrum.

For full TL curves, yes, that's the way to do it, but with since sweeps, not IR pulses. That will, indeed, give you the full picture.

But if you just want to get a rough idea of real-world isolation, set up your sound system inside the room playing a selection of bass-heavy music at about 100 dBC in the room (wear ear protection), then take your hand-held meter for a walk around the house, inside and out, while you note done the levels at various points, and listen with your ears too.

Subtract the "readings at each point" from the "100 dB in the room", and you get a pretty good estimate of isolation. Do all the above with the meter set to "C" and "slow".

From a usage perspective, If I am able to mix into the night and not disturb my neighbours whilst mixing at 78dBC I will be very very pleased.

I don't see that as being a problem. Very do-able. Very realistic.

A: I may have misled. I never have two people mixing, despite what my little model suggests. Client will always sit at the sweet spot whilst i operate the preview playback.

Ahhh! That makes more sense. You should probably update your model to reflect that, as it is confusing at present, with a "tandem mix engineer".

A: This is a perfect example of what I had hoped to glean. Thanks. Now that you point it out, it is quite obvious really. Shame, as I love the look of a QRD.

I love them too! But I don't get to use them in many of my designs, as the rooms just aren't big enough to have enough distance between the devices and the ears of critical listeners. Here's one recent case where I got lucky: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 You can't see them in those photos, but there's a set of six inverted QRD's on the rear angled walls, above the doors (3 on each side). Just far enough away from the couch to be good, and tuned high enough. That's a nice sized control room, that does allow for such luxuries, but that's not always the case. Sometimes I see control rooms with a huge Shcroeder diffuser on the rear wall, and the couch just a few inches away... You have to wonder how any producer could make mix decisions in that type of environment... all he has to do is lean a couple of inches left or right, and get a totally different acoustic response... sigh!

<RANT MODE = OFF>

A: Hmm. Sounds like this will be an issue, as I am unable to remove the carpet. More thinking required.

Think outside the box: Think how to remove it, while still meeting the condition of "leaving the room in the same condition you found it", or in even better condition... No reasonable landlord/owner would refuse a sincere and realistic agreement.

A: I was planning to build a frame around the existing window frame on the inside, that has a layer or two of board to provide a greater density at those apertures.?

... thus creating a 3-leaf system... Yeah, that might actually be an option if you can't touch the window, but you'll have to take into account the 3-leaf problem...

A: My sleepiness may have confused. My question was whether using Particleboard for the walls would be feasible. The boards in question are common flooring boards. I am trying to avoid Plasterboard as its a mess to pull apart and not easily reusable.

Ahhh! OK, so it was sleep-induced drywall flooring! No problem.

Mass is mass. Mass is what you need. What matters is "how many kg per square meter of wall area", and "sealed air-tight". Use whatever building material meets give you the right numbers, and meets your budget. I foten use one layer of OSB or plywood on the studs, plus one layer of drywall (plasterboard) on top of that, for several reasons. The OSB gives you sheer strength in the wall, as well as a nailing surface around 100% of the wall, and the drywall provides a nice finish surface and lots of mass. Use whatever material will do the job. We normally recommend drywall for two reasons: 1) it is usually the cheapest mass (kg for kg), and 2) there's a lot of research available on how it behaves acoustically. It is well understood. But other materials work well too.

The intention was to save money by only carpeting 50percent of the floor, usually covering the operating area of the room.

What would you use for the other 50%? Laminate flooring, maybe? The installed cost for carpet and laminate flooring is very similar, per square meter. And you can very easily take out laminate flooring, and take it with you, when you leave... Simple, fast, cheap, excellent acoustic properties... food for thought. You can even install laminate yourself (it is dead easy) to save some more money, whereas fitted carpet is more of a specialized job.... you'd probably have to hire someone to do that.. $$$

I can see that the current ambient noise floor hovers around 33dBC SPL when I am still, and 45dBC when typing. ... So, If I was to be mixing in my room at an average of 78dBC, momentary peaks of 86dBC, then for silence here in the kitchen I would want to have around 50dB of TL if I didn't want to be a nuisance. ... Am I dreaming I suspect so.

Not so bad, actually! 50 dB of isolation is entirely do-able. It is realistic, and a good, achievable goal.

A: Right. So, in additional to the two leafs (Masses) being airtight, the air gap (Spring) itslef needs to be sealed to provide compressive resistance to the two masses. Is that right?

Air is a spring always, even when it is not contained, as far as sound waves are concerned: Sound waves can't move any faster than they do, simply because they are up against the compression limit of air! The speed of sound is 343 m/s because going any faster means that you have to over-compress the air and "break through" the "barrier". To go any faster, you create shock waves in the structure of the air itself... You force the air molecules to smash into each other faster than the want to, because you overcome the "spring" that keeps them from doing so otherwise...

All that to illustrate that air is a spring, even when it is not contained in sealed chamber. It has resilience, regardless of its container. So the air inside the wall is still a spring, and resonance still happens, even if one of the leaves is not air tight. A kick drum with a huge mic hole in one head still resonates and "booms" inside.

It's more an issue of efficiency, not actual resonance.

The reason why you want to have everything sealed air-tight is even simpler: if you have a tiny crack where air can get through, then so can sound. sound travels through air very well, so if there is "air" connecting the two sides of your wall through a hole, gap, crack, etc., then sound WILL move through that "air bridge", and come out the the other side, loud and clear.

That's the main reason why you want to take extreme care to ensure that both leaves are perfectly hermetic.

You will go through many boxes of caulk to achieve that. Buy shares in the caulk company now, because their stock will rise simply due to your huge consumption!

I will do some research into MSM Resonance and see what I can learn.

Start with the Wyle report, from way back in 1973. Very old, but very valid principles.

A: Thanks for explaining it like that - makes sense when described in that manner. I will read up further on the RFZ approach, and see how this may be a direction for me to pursue.

In my opinion, it's the best design principle out there right now. It just makes sense that you only want the pure, clean, unadulterated sound of the speakers to reach your ears, and no reflections or coloration. It's just logical. Most of the rooms I design are RFZ. The one in the link above is RFZ. And you can see fro the results, that it works.

Would you be able to recommend some reading - or a google search string? Often knowing the right question is the hardest step.

Right here! The forum is a great resource for learning about RFZ design. Most of John's rooms are RFZ based, most of mine are, and you'll see many forum members who have followed that philosophy in their own rooms. There are some excellent explanations on some of those build threads, as well as many examples of common pitfalls and how to avoid them in the real world.

A: Thats good to hear as that's intuitive and aligns with my current plans. How would I search to find the methods to do the math on this Stuart?

The basic equations for MSM resonance are: That's for the simple 2-leaf system, and the more complex (and less desirable) 3-leaf system

That gives you the MSM resonant frequency(ies) of your wall (or window, door, ceiling, floor, etc.). You want that to be at least one octave below the lowest frequency that you need to isolate. In other words, if the lowest frequency you need to isolate is 70 Hz, then you need to tune your walls to have MSM no higher than 35 Hz. So you increase the mass, or the air gap, or both, until you get that.

Then you combine that with these equations: And you have your answer! That tells you how much isolation you'll be getting in each of the three regions from this diagram: Check your results against your own musical spectrum, and the Fletcher-Munson equal loudness curves, and Bob's your uncle!


... with caveats, or course...

- Stuart -

* * * *

Regardless of the impact on the carpet, will there be any negatives in terms of isolation?

Yep. Remember the whole "hermetic seal" thing? Carpets aren't exactly known for being air-tight, not even when squashed flat. Think of this: If you have a solid concrete or solid brick wall as part of your isolation system, it will absolutely be necessary to seal that surface with some form of masonry sealer, such as paint, for example: This is because the solid reinforced concrete is porous! If you don't seal it, you don't get good isolation, despite the mass and density. The porous nature of the concrete partially defeats the isolation. Now compare the "porous nature" of carpet to that of concrete, and draw your conclusions...

In this design, where is the 3rd leaf?

Go back to the previous post. It says "The Ceiling is plasterboard, which then turns into the upstairs front room with is timber floor,". That's two laves. You say you want to add a new ceiling below that: that makes three leaves.

Is it due to the greater mass of the thick brick walls that constitute the 2nd leaf in comparison of the inner leaf?

Nope! We are talking about ceiling structure here. The "3-leaf" issue is due to the three leaves. From top to bottom: 1) existing timber floor. 2) Existing plasterboard ceiling. 3) Proposed new plasterboard ceiling.

The industry standard of the Rational Acoustics SC-1. Works a treat and has been ultra accurate when i compare to any B&K beastie.

That's a calibrator, not a sound level meter: You seem to be missing the point: You need a sound level meter that you can walk around with you and take measurements in various locations, not just a mic that is hooked up to your DAW. You need a plain old simple hand-held sound level meter that can go anywhere. I'm not sure why you object so strenuously to getting one: they are not expensive, and are very necessary. They go places your DAW cannot go...

I find this method always prone to confirmation bias, and return to the Sweeps for quantative measurements.

Well, I guess if you only ever plan to mix pure sine waves in your studio, that would be fine... but if you do ever feel the need to mix real music in there, which consists of numerous simultaneous frequencies that interact in extremely complex ways, both acoustically and psycho-acoustically, then you should probably do the measurements the old-fashioned, tried-and-trusted way: with real music, and a real sound level meter....

Way too many people think that numbers on a meter, or wavy lines on a graph, are the best way to measure sounds. But the problem is that human ears do not work like microphones, and human brains do not work like DSP's. We have subjective interpretations of sound, which is what the science of psycho-acoustics deals with, and since real sounds can be far more complex than simple sine waves, there is a lot more going on, subjectively, than what simple sine waves can show. If that were not the case, MP3 compression would be impossible.

i need to understand how what appears to be 2 Leafs, acts as 3.

I'm not sure where you see something that looks like 2 leaves but acts like 3. A "leaf" is just a massive surface that has an air gap on at least one side, followed by another such massive surface. Any time you have an air gap between layers of mass, you have leaves. The number of leaves is defined by the number of air gaps, plus one. If you have only one air gap, that implies there must be two leaves (one on each side). If you count three air gaps, that implies there must be four leaves....

I would only use solid timber,

As long as that is laid solidly on the subfloor, with no air gaps in between, that would be fine. Expensive, yes, but acoustically fine. But if you need some type of framework under that flooring, then you have a problem....

The question in my mind is always the LF, how much isolation is achievable in my budget for below 120Hz.

The equations I showed you above will reveal that!

I forgot to give you the one for single-leaf:

TL(dB)= 20log(W) + 20log(f) -47.2

W is the weight density of the panel, and
f is the center frequency of the third-octave measurement band

That one is more commonly known as "mass law". and is not very encouraging. Which is why we never recommend a single-leaf isolation wall for high levels of isolation...

If a room isn't an RFZ what is it?

It could be LEDE, CID, NER, MR, or any one of several other philosophies.

Surely you can't build a studio to monitor audio critically and allow for primary and secondary reflections to be present at the mix position?

If you don't build it as RFZ, then that is exactly what you get! The basic goal of RFZ is that there can be no first order reflections arriving at the mix position within 20ms following the direct sound, louder than 20-dB below the direct sound, and after that ITDG (Initial Time Delay Gap), the revereberant field must be fully diffuse and even in both the time domain and frequency domain. There are many other aspects to it, but that's the most important part. If your room is not specifically designed as RFZ, then it will never end up as RFZ by sheer luck. It takes a lot of doing to make that happen. The room must be carefully shaped to create the initial RFZ with no first order reflections above -20 (at all frequencies!), and then carefully treated to provide the fully diffuse, even, smooth sound field following after then 20 ms Haas time. It also pretty much implies that your speakers will have to be flush mounted ("soffit mounted").

It's not as easy as it sounds, and is seldom achieved fully. Sound moves in 3D, not just 2D, and interacts with everything in the room. Speakers are not perfect, walls are not infinite rigid, and treatment is not 100% perfect.

This is going to take some time to get into.

Yup! Realistically, it takes about 3 to 6 months of constant studying to grasp the basics of acoustics, sufficient to design a studio. Then it takes another 3 to 6 months to actually design it. There's just so much to take into account, and so many unsuspected ways that things interact with each other. Acoustics is not even intuitive: whoever would think that you could take a wall that is isolating very well, add an extra leaf inside it, with substantial mass, and end up with a wall that isolates WORSE? Not intuitive, but very true. It takes a while to get your head around that...

I have just bought some books for my upcoming holiday to allow me to extend my knowledge.

Hopefully you have "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais, on your list! Read those two first... Along with the Wyle paper, and also ITU BS.1116-2, and IR-761...

One thing I realised to note was my intended NC/NC rating, most rooms I have build and worked in have been down around the NR22 area, and I find this very workable. Is this kind of level achievable in your view for a project on the scale of mine?

NC22 (or NR22 if you prefer: nearly the same) is probably attainable, but that's not just a function of the actual room isolation: it's also a function of your HVAC system. You need to keep the air flowing slowly enough so as to not increase the noise level above NC22, but art the same time in large enough volume so as to meet the ASHRAE recommendations for that type of room, based on internal volume and occupancy.

More math!


- Stuart -

I just realized I never commented on your FuzzMeasure graphs:

First, those are only the frequency response graphs, so they only show a small part of the entire acoustic story (and not necessarily even the most important part...). But even so, useful to see. If you could export the actual impulse response data and post that someplace I can download it, I'd be able to tell you a lot more...

Also, at 1/12 octave smoothing, you aren't seeing all the low frequency detail, such as room modes and possible multiple resonances in the walls. Use 1/48 for lows, 1/24 for mids, 1/12 or 1/6 for highs, then 1/3 for overall impression.

Using a Sinewave Sweep 1-20000Hz over 10secs with 3 averaged sweeps,

You don't need to go down that low, and you do need to go higher. I normally measure 17 Hz. to 22 kHz. Your speakers certainly aren't putting out any useful energy below that, and you wouldn't be able to hear it even if they were, plus your setup would not be able to give you accurate readings on that...so you are just wasting data by measuring below about 15. And there is stuff going up above 20k that is useful to see.

But, the lower frequencies are interesting. In the Mix Room there is a steady rolloff from around 100hz.

It seems to start more like 180 Hz, but there's some modal or SBIR stuff around 100 (which is typical of small rooms) that's masking it.

This is more pronounced that I usually see with these ATC's, so I conclude I measured in a node.

Nope. Modes are very high Q (around 3 Hz or so), so you can't be in a node that covers all the way from 10 Hz to 180 Hz! That could be any number o things, but I'd guess that it is related to the speaker setup, and/or bass management, and/or room loading.

Moving Outside the room, to adjacent rooms and hallway, I see a pronounced peak of around 45-55hz. This peak is common to all the measurements, and is significantly higher than what I would expect. Could this be some resonant frequency of the actual house?

It's more likely to be one of the resonances of the wall. Like all undamped resonances, you can dearly see how it not only trashes the isolation, but actually amplifies the sound at that frequency. You only get isolation starting at 1.414 times the resonant frequency (unity point), usable isolation at 2x f0,and decent isolation at 3xf0.

They only trouble is, I can't figure out why that frequency is so high, based on what you said about the construction! If you have 1 foot thick (300mm) solid brick walls for your outer leaf, and no inner-leaf, then that makes no sense! If you had drywall on studs or battens attached to that brick wall, then yes, absolutely you could have major resonance going on around 40-60 Hz (depending on configuration), but from a solid brick wall? Not logical.

So maybe it's not your walls: Maybe it's your floor, or your ceiling... Especially considering that you get the biggest peak in the room directly above...

Measure the size of those joists, and the thickness of the floor boards above them, and the drywall below them.

I suspect that the first goal would be to address those wild 50Hz resonances in the house coming from the Studio down to point where there are even with the rest of the rooms response,

Yes, but you can't do that without doing the rest too! If it is a ceiling resonance (as I suspect) then it will need to be addressed by adding mass to the underside of the floorboards, and adding damping to the air gap. That implies taking off the drywall from the ceiling in your existing room, to get access to the joist bays...

Then, if you choose to put the drywall back again (thus creating a 3-leaf system), you'll need to compensate for the reduce isolation (and higher f+ / f- frequencies) by adding extra mass to that existing ceiling, and using a larger-than-otherwise-needed gap to the new inner-leaf ceiling.

MSM is a tuned system, and as you can see, it is very powerful. You have to tune it right, if you want the results you are looking for. And "tuning it right" implies doing some stuff that you say you don't want to do.... unfortunately, you can't eat your cake and have it too...

If you don't want to do what needs to be done, then you can't expect to get the results you say you want!

and then decrease the overall transmission to a point where the other occupants in the house can't hear what I am doing if I am mixing at a conservative 78dBC SPL.

That comes as an automatic consequence of tuning the MSM (or MSMSM) system correctly, with enough mass and air gaps. If the resonant frequencies are correct, and the overall mass is correct, then the result is isolation in the right part of the spectrum.

What do you think? Do these measurements indicate major issues, or a positive starting point.

Yes!

In other words, it is both....

(I love to be cryptic...)


- Stuart -

* * * * *