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PostPosted: Thu Dec 03, 2020 2:02 am 
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Location: Greece
Hello everyone,

I'm Yorgos. This is my first post in this forum. I'm reading this for quite some time and I'm also reading Rod Gervais book, trying to learn as much as possible regarding acoustics, construction etc. So first of all, I'd like to thank all of you for sharing the knowledge.

Some info about me: I live in Athens, Greece. I'm a songwriter and I record/produce my own music (and selectively some other people's stuff). I've also done the sound design for a couple of movies.
My monitoring system is a pair of Focal CMS50, but I'm planning to swap them for something that goes lower. No plans for sub yet, since I don't have the right space for that. I mix at about 75 dB(c) (max).

After about 15 years of using my living room as a home studio, I need to move on and make a proper space from scratch.

What I'm mainly interested in is having a control room where I can also cut some takes (for convenience and for better communication with the musicians). I want it to be quiet enough for recording soft vocals and acoustic instruments (classical guitar etc).

There is an available space of 190 m2 (about 2000 ft2), half of which I can use as a studio - the rest will remain a single space for a pottery workshop. So, I can build something about 90-100 m2.

Since this is a fairly large space for just a control room, I'm thinking of building a live/rehearsal room, either for myself or to be able to record choirs, maybe a small band, a set of drums etc. And if there's enough space left, I could make an ultra-isolated booth for recording foleys.

The space is on the second floor of a building, with nothing else attached to it.
The foundations of the building are on a concrete slab.
There is nothing built on this floor. Just the external walls, which are 25 cm (10") thick, made of brick (9 cm) - Expanded polystyrene (EPS) (5 cm) - brick (9 cm), rendered only from the outside. There's no option from the owner to be rendered from the inside.

As you can see in the pictures, there are four concrete pillars in the space, many concrete studs coming out of the walls and concrete joists coming down off the ceiling.
The floor is concrete.
Height is about 2,95 m.

On the ground floor there's a grocery store.
The first floor is empty, just like the one on the second floor.
There's no third floor.

There's one big drawback:
The building is beside a very noisy street with a lot of traffic.
Also, outside the grocery store there are some huge refrigerators, that emit a constant buzzing sound, the main frequency of which is about 140-150Hz, at about 58-60 dB(a) (measured at about 60 cm / 2 ft. away).

Street noise measured at the balcony of the 2nd floor is about 65-67 dB(a), with the peaks (horns, motorcycles passing by etc) going up to 72-76 dB(a).
The same noise measured inside the building is 56-58 dB (idle) and 64 (peak) respectively.

All dB measurements are taken with the Radioshack Sound Level Meter 33-4050.

Street noise is (just like every street, I guess) like a constant brown noise, but with some emphasis in the 1-1.5 KHz range (with the exception of some mid-low freq bumps when some heavy tracks are passing by - which is pretty frequent.

At this time, I have no other choice, but to build something there, since it's a space that was given to me without rent and with the freedom to do whatever I want in it. So, it's there or nowhere else.

My budget is too limited to get a professional do it for me (I will do everything by myself, so there will be a lot of DIY). But I do not want to start making something without being absolutely sure of the end result. I would like to ensure that the construction will have sufficient insulation so that I can work undisturbed and record with no sound coming from the street (The workshop at the same floor won't disturb).

I'm attaching the plans of two different approaches of what I have in mind, atm. The workshop has to stay at the right side, no matter what.
The designs are over-simplified (there's no acoustic treatment etc), just to give you an idea. Both of them are just a starting point, because I don't know if this place is suitable for building a studio yet.

The interior walls will be 40 cm (16") wide with two layers of gypsum-board (1,25 mm (1/2") thick each) on each side and filled with low(est)-density rockwool (pink fluffy is not available in Greece). The STC of it (correct me if I'm wrong) is about 58. The gypsum-boards will be fixed on steel studs.
Based on a TL calculator found in this site, the resonant frequency of the wall is 23,32 Hz, so the lowest frequency it can isolate is 33Hz.

The exterior brick-wall (25 cm) will be treated the same way as the interior: At a 40 cm distance from the inside of the brick-wall I will build a 2-layer gypsum-board and fill the gap with rockwool too. That gives us a resonant frequency of 17,35 Hz and the lowest frequency the wall can isolate is 24 Hz. I can't find any info regarding the STC.

There are no doors or windows installed yet, just the openings, so I'm free to decide whether an opening would serve as a window/door or just shut it and build a wall instead. I guess, shutting all the openings and making them like a wall would increase the insulation, but I'd like to have some natural light in the studio, as much as possible.
Probably, these openings will be the weakest link in the chain, so I'd like to know whether there's a way I can sufficiently block the street noise (and hopefully not cost a fortune).

I've found some STC Ratings for glass and window constructions, but I don't know how these figures translate into the real world (and what dB I am aiming for) - since STC mainly applies at about 500Hz but the street emits a constant brown noise.

About the structure-borne transmission, I've done a simple (and maybe silly) test by hitting hard with a hammer the floor and the ceiling of the other floors and surprisingly my recorder didn't capture any sound at the 2nd floor. I don't know if that proves something (I was informed by the owner that the concrete slabs on each floor were a bit thicker than the usual). Since the place has no windows to be closed, I can't think of any other way to figure out whether the traffic noise is transmitted through the structure or not (air-borne sound is pretty loud to hear something else). The best scenario would be to leave the floor and ceiling as it is, if there's no need to isolate it any further.

Nevertheless, there's a case in the (near?) future for an elevator to be installed (if the first floor is occupied). Is this something a have to worry about? In that case, is there a viable solution? I guess I can't float the floor, since I'm building on an upper level.

So, having in mind that I can't afford to do a lot more than the above mentioned, I'd like your precious opinion:

1. Is building a small studio at this place doomed to fail or not?

2. Is having windows facing at this busy street a no-no option? (Regarding sound isolation)

3. About the external brick-wall: Does the fact that there's a 5cm EPS between the bricks mean that there's already a 2-leaf system? In that case, I can't build anything on the inside, since it will create a 3-leaf system.

4. Since floating the floor is pretty much a no-option, will the operation of an elevator emit a structure-borne sound that would destroy the recordings?

Any other opinions/thoughts/suggestions are more than welcome.

At this time, I'm mainly concerned whether I should move on with the construction.
If you suggest that it's ok, I will come back with more detailed design and plans and I'd be very happy to discuss any groundbreaking idea.

Thanks a lot for your time reading this.


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PostPosted: Sun Dec 06, 2020 12:53 am 
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I recommend changing to a Sound Level Meter which can hear full range, dBC or dBZ weighting. Also Leq is better than watching rapidly changing instantaneous numbers. There are many available for Smartphones. https://www.cdc.gov/niosh/topics/noise/app.html

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PostPosted: Mon Dec 07, 2020 5:01 am 
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Location: Greece
Thank you for your reply.

I've taken a few more measurements with dBC weighting and slow response.
Street noise measured at the balcony of the 2nd floor is 74 dBC.
With heavy traffic (motorcycles, heavy vehicles passing by etc.) it goes up to 77 dBC.


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PostPosted: Tue Dec 08, 2020 9:26 am 
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You are welcome. Do you have an iPhone?

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PostPosted: Tue Dec 08, 2020 7:07 pm 
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Location: Greece
DanDan wrote:
Do you have an iPhone?


No, unfortunately. The app on the link you mentioned above is only for iPhone. I have a Xiaomi. I've checked nearly every app for android and they seem to be inaccurate (each one is giving different results).


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PostPosted: Wed Dec 09, 2020 8:17 pm 
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Hi,

Really nice space you have to work with. The double brick walls with the XPS in between will not prevent you from building a decoupled inner leaf, and in fact is a great starting point.

Of course you have many large openings in the building as it currently stands, but once they are bricked up (or, have suitable windows/doors) and all sealed air tight you'll have a very dense outer leaf which will be excellent for isolation.

Personally I see little point in taking many measurements at the moment, though it won't hurt anything, but until the outer leaf is air tight we're not going to be able to know what construction is needed for your inner leaf.

To simplify things:

Air tight, heavy, dense brick outer leaf + insulated air gap + 2-3 layers of drywall on timber frames = near silence.

The mechanical vibration and noise from the rest of the building does pose a potential problem, but I highly suspect once your inner leaf Is built there will only be minimal disturbance.

Regarding your question about windows facing the busy street - no, it's not a problem at all. We would just need to do some calculations so that the window assembly equals the same as the wall assembly. This can be achieved with 2x dense, laminated glass and a large cavity between them. In other words, a window does not mean less isolation.

It all relies on proper design & execution.

Paul

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PostPosted: Wed Dec 09, 2020 10:25 pm 
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Paul, thanks for your reply.

Paulus87 wrote:
The mechanical vibration and noise from the rest of the building does pose a potential problem, but I highly suspect once your inner leaf Is built there will only be minimal disturbance.

Something I didn't mention previously: The first floor (which is identical to the second one) has all the openings sealed with 1" MDF and the street noise is <50dBC (which, I guess, is a good sign, regarding soundproofing). The sound from the refrigerators is still clearly audible. That's why I'm worried about the structure-borne transmission (but is it structure-borne or air-borne? Can't figure out) from the (future) elevator or the street, especially when I can't float the floor.

Paulus87 wrote:
It all relies on proper design & execution.

I totally agree, that's why I'm trying to learn as much as I can, to be sure I won't waste any time/money.
As I've written in the first post, my budget is very limited (it's already stretched for just the construction), so I can't hire an acoustician, whose work I highly respect. If I could afford it, I wouldn't post here. I suppose that this applies to many other members and situations.


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PostPosted: Sat Dec 12, 2020 3:25 am 
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The reason why I was pushing for better measurements is that the current ones look low to me. I have measured in the 90dB region from a single car passing a laneway in the City here.
As Paul says your space is fabulous. But it would require a pretty large investment to isolate and provide cool air. This doesn't jibe with not being able to afford an acoustician.
You might ask a couple of us about charges and the various levels of consulting. Making acoustically 'wise' choices can save money.

It is possible to listen to structure borne noise. Using a drumstick or pencil or such make a physical bridge between the structure and outside your ear canal.
There is also a Mechanic's stethoscope for listening to gears etc.

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http://www.soundsound.ie


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PostPosted: Sat Dec 12, 2020 3:45 am 
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DanDan wrote:
It is possible to listen to structure borne noise. Using a drumstick or pencil or such make a physical bridge between the structure and outside your ear canal.
There is also a Mechanic's stethoscope for listening to gears etc.

That's a nice tip. Thanks!

DanDan wrote:
The reason why I was pushing for better measurements is that the current ones look low to me. I have measured in the 90dB region from a single car passing a laneway in the City here.

That's interesting. Even on C weighting, I didn't measure anything above 80dB.
In the next days I'll take some REW measurements, so we'll have more accurate data to discuss on.

DanDan wrote:
As Paul says your space is fabulous.

I'm glad you say that too. It's very encouraging. Hope, the 2.95 m height is not so low.


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PostPosted: Fri Dec 18, 2020 3:48 am 
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Regarding the design of the studio, I think that the concept of one-room studio would apply better to my needs.

This is a revised design for the one-room studio concept.

The concrete pillars are the the main constraints I had (which in a way lead me to this design). I tried to "hide" them as much as I could. The "control room" part will be placed in the upper side (unless you suggest it's not a good idea).

The left wall of the main room follows the orientation of the pillars, so it's angled, related to the front (upper) wall. Right wall is angled too - left and right wall angle is about 17 degrees.

1. I'm worried about the opening in the front wall, which is not centered.
Will this cause an issue regarding stereo image?
And if so, would a heavy curtain solve the problem?

2. Then, there's a 2' x 2' pillar in about he middle the space.
Is this a big problem regarding acoustics? Should I cover it with broadband absorbers?

Any opinions are more than welcome.
Feel free to suggest anything.


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PostPosted: Fri Dec 18, 2020 8:42 am 
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Absorbers have a 'frequency response' Thin ones are like tweeters, absorbing only HF. Folded curtains can behave like a thicker absorber but would be a very expensive form of absorption.
Your space is quite big. I recommend treating just a small area of it for Mixing. You could create a 'cave' using wood frame and dense absorption as the 'walls'.

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PostPosted: Fri Dec 18, 2020 9:34 am 
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DanDan wrote:
Absorbers have a 'frequency response' Thin ones are like tweeters, absorbing only HF. Folded curtains can behave like a thicker absorber but would be a very expensive form of absorption.


There's another expensive solution I can think of: Making the opening larger, by breaking down the wall on the right side.
Then the opening would be right in the middle of the wall.
Should I do it or is it too much bothering?

DanDan wrote:
Your space is quite big. I recommend treating just a small area of it for Mixing.


Acoustically speaking, I thought that a bigger room, like this, would create less problems than a smaller one.
And since I'm not mixing at loud levels, it would be more difficult to "activate" the room modes. Correct me if I'm wrong.

But, if I understand correctly, do you say that "big" in this case is a bit of disadvantage (being too big)?
Instead of creating a cave, would it be preferable if I made a larger booth (by moving the left adjoining wall towards the right), in order to make the mixing area less wide?


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PostPosted: Sat Dec 19, 2020 1:42 am 
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i answered this at GearSlutz but i'll re-post here as well. i'd lose the lock space and reclaim it in the booth. plan B is the one closest to what i think you should go with.
Attachment:
the tenant studio plan B+.jpg


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PostPosted: Sun Dec 20, 2020 5:08 am 
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gullfo wrote:
i answered this at GearSlutz but i'll re-post here as well. i'd lose the lock space and reclaim it in the booth. plan B is the one closest to what i think you should go with.
Attachment:
the tenant studio plan B+.jpg


Hey Gullfo, thanks a lot for making the plan from scratch! Really appreciate that.
(By the way, apologies for forgetting sharing the .skp file).

I've already read your post in GS, too. I'm posting the same questions here, in order for the other members to keep up.

1. In my plan, the upper external walls are 40 cm (15,6") wide, whereas in this plan they're half of it. Do you believe that the initial size is overkill? Or is it something designed by mistake? I'm asking because the other external walls are still 40 cm wide.

Regarding STC values, the only info I've got is the relations between STC and different constructions (2-leaf vs 3-leaf, double drywall vs single etc). But I haven't found something that relates STC with the width of a wall.

I mean, a 40 cm wall has a F0=23Hz and a 20 cm a F0=33Hz.
But what about their STC Ratings? Logic says that the thicker the wall, the higher the STC, but this increase may be negligible.

2. I really like the angled back wall of the CR! But it's blocking the upper opening. Apart from having a bigger CR, is there any other reason to "lose" the opening? (The Workshop owner won't be very happy about it...)

3. The window in the booth is facing at a very noisy street. Even though it would be nice to have natural light in there, I was thinking to brick it up. Did you leave the window opening by purpose? Would it make the total isolation of the booth a bit more difficult (and pricey?)

4. CR/LR and booth/CR walls are double alright and wide enough. But shouldn't I make the Restroom wall and the one to the Workshop with the same width?

5. I see that you're keeping the separate CR/LR idea in your plan. What do you think about the one-room concept I'm working on?


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PostPosted: Sun Dec 20, 2020 6:13 am 
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I was thinking of the one room studio. In such a large space I recommend treating just a Mixing Zone. A sort of absorbent blocking 'cave"

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