Soundman2020 - Studio Design Forum

Hi everybody.

Relocating my business to nicer, newer, more cosy premises with natural light

The building is 20 years old, solid build, concrete & steel, the office is on top floor (only two floors), ceiling 3,5m high concrete, also concrete floor with parquet finish.

One of the rooms would be used as a podcast/VO recording. Overlooking a not so busy street, but natural sunlight i dont want to giveaway

The ideal plan would be to have this room isolated, from the outside noise, as much as possible.

The room as is now : (See pic attached)
one side - concrete wall with rebar, (with windows)
other three walls - 2xPB _light steel framing with fluffy insulation_2xPB (together 13cm).

The windows are in aluminium frame, 73cm x 220cm, normal glass 4mm-16mm-4mm.

There is no plan for recording music, the main goal is to mute the sounds of scooters passing by, and ambulance from the main street which is about 100 meters away with tall apartment blocks in between.

I dont have the exact SPL readings, but from what my app on my phone can tell , the noise floor with windows closed is about 40db (c weighed) and want to drop down to 33db.

Low frequencies are not so problematic, since we will mostly record VO. Faraway sirens and speech/ walking in neighbour offices are my most concern to get rid off.

Since we will do some reconstructing anyway, i want to plan ahead.

So i was thinking building a room inside the room:
- new decoupled walls (lightsteel frame with insulation, double PB on the inner side, backing rod and caulk) with one window opening, two other i would close completely.
- decoupled ceiling (no one above us but concrete&rebar roof) double PB with GG in between?
- heavy door

Just an idea if i am plannign in the right direction?

thanks in advance for any comments

Hi Bivis, and Welcome to the forum!

It's great that you have a place you can set up as your studio! Hopefully, here on the forum you'll find all the information and help that you need to make your dream int reality.

solid build, concrete & steel,

That's a good start, for acoustic isolation. High mass and high density are always good for that.

ceiling 3,5m high concrete

Excellent. A high ceiling is also good, acoustically.

Overlooking a not so busy street, but natural sunlight i dont want to giveaway

That's fine. You can certainly have glass in studios and still have good isolation.

other three walls - 2xPB _light steel framing with fluffy insulation_2xPB (together 13cm).

That's the weakest part of your structure, acoustically. That is going to need some work, to get good isolation. Fortunately, it isn't difficult to do what you wold need to do there.

normal glass 4mm-16mm-4mm.

I assume you mean they are "double-glazed" ("IGU") panels, with two glass panes of 4mm thickness, separated by an air gap of 16mm? That's not so good, and might need replacing if you need high isolation.

the main goal is to mute the sounds of scooters passing by, and ambulance from the main street which is about 100 meters away

It would be a good idea to measure the sound levels of those sounds, at their loudest levels. Have your meter ready, and each time you hear an ambulance coming close, open the window and measure the level. Note down a few of those, so you have a record of how loud it can get. The same for the traffic sounds, and any other external sounds (eg, planes or helicopters flying over occasionally, wind, rain, thunder, hail, loud music from car radios/ neighbors, dogs barking, etc.) Any type of occasional, intermittent sound should be on your list, so you have a good idea of what is "out there". Also note what the predominant frequency is, for each of those readings.

the noise floor with windows closed is about 40db (c weighed) and want to drop down to 33db.

Did you take that measurement at the time the "loud things" were happening outside, or at a very quiet time? You say "noise floor", so I'm assuming it was very quiet, and that's the level you are aiming to have inside your studio when it is finished?

Low frequencies are not so problematic, since we will mostly record VO

So you will be applying a high-pass-filter (also called a "low cut") to your mics? If so, what frequency will you set that for? That will give you an idea of what frequency range you should be concerned about for your isolation. You should aim to isolate well starting from a frequency that is about half of the lowest frequency that you expect to have in your recordings. So, for example, let's say that you want to set your low cut filter to roll off below 120 Hz with a steep 24 db per octave slope. That implies that at 60 Hz it would be reducing by 24 dB, and at 30 Hz it would be reducing 48 db, which is pretty quiet. So you could design your isolation system to work down to 15 Hz, or maybe 20 Hz, to ensure that there is no problem in your recordings. If there is already not much low frequency in the sounds outside that you want to isolate, then you might even be able to choose a higher frequency for your isolation limit. Eg. 30 Hz. That way, your room would isolate well from about 60 Hz upwards.

So i was thinking building a room inside the room:
- new decoupled walls (lightsteel frame with insulation, double PB on the inner side, backing rod and caulk) with one window opening, two other i would close completely.
- decoupled ceiling (no one above us but concrete&rebar roof) double PB with GG in between?
- heavy door

That is, indeed, the right plan! You can figure out the frequency and isolation of your wall design fairly easily. I wrote a brief article about that a while ago: What is MSM? How does it work? That should help you choose the materials and cavity depth, to get the isolation you need. The only thing I would suggest changing in your plan, is to replace your single heavy door with two doors, back-to-back, one door in each leaf. Something like this: site built door for high isolation Yours would not need to be quite so extreme, as that design was specifically for a very high isolation situation (drum studio in a residential area), but that's the general idea.

Just an idea if i am plannign in the right direction?

You seem to be on the right track!


- Stuart -

Thanks so much for all the answers and info.

Planning to do a sound analisys of the premises really soon.

In the mean time i had another idea regarding the size of the vocal booth and the location. (see attached)
I would still like to go for a room in a room approach, just smaller.

the far left window i have greyed out, because i would block it completely before putting up the new wall.

bivis wrote:Source of the post I would still like to go for a room in a room approach, just smaller.

Is there a really good, overriding reason why you need that room to be smaller? Small rooms never sound good. Small vocal booths will always sound "boxy" and unpleasant, and the only feasible treatment usually is to just make it very dead, perhaps with some slight return of the upper end of the spectrum, so it doesn't sound too awful. Unless there's an overwhelming reason for doing that, I would suggest against it.

Also, your diagram does not show a proper "room-in-a-room" scenario. You would need to build a second diagonal wall in front of the one you are showing, to seal off the booth area, which implies that you would need to flip the door in that existing wall so it opens the other way, into the booth... which greatly reduces the useful space in the room, as the door would be swinging across a wide path. The other option would be to use sliding glass doors, instead of hinged doors.

Your diagram also has a label saying "double PB" on the wall with the door, with arrows pointing to both sides of the wall: that would produce a coupled 2-leaf wall, which basically acts the same as a single leaf wall: poor isolation. Not a good idea.

- Stuart -

Thanks for your reply and informative suggestions.

The room as shown in the new plan is twice as big as we use now
and we would like to use the other part of the room as an additional office space. No need to have 15m2 of iso booth for our purposes, but i understand what you mean with boxy sound.
Although we have heard some vocals recorded in tiny boxy spaces
https://youtu.be/3su4q5fVGQg?t=132

Additionally i want to apologise for the lack of my graphic skills. I inserted small blue lines where the diagonal wall would (not) meet the existing walls, and forgot to put question marks there, because.i have no idea how to finish the connection.

Also the arrows and text should have ?? at the end of that, since i am asking for advice, and only have an idea of it, rather to tell you how i am going to build this.

regarding the greyed out window, i thought i would build a window insert, to isolate as much sound as possible there.

any info would help, thanks in advance

Zdravo bivis,

is this what you want to build - with the yellow area as the vocal booth and the green area as an ordinary office space?

Zdravo zvezda

Dakujem for the picture.
Yes. This is exactly as i would like it to turn out.

Would the 5cm air gap suffice?
Normal pb or denser?
Steel gague would be 7,5cm or even 10cm for stronger support

bivis wrote:Source of the postWould the 5cm air gap suffice?

I will leave it to the expert, Stuart, to advise on the optimum gap given the booth is going to be so small.

bivis wrote:Source of the postNormal pb or denser?

If denser boards are not too expensive then they will be ideal, either fire-resistant or acoustic. I am sure Stuart will advise that you put up a sheet of OSB before the two layers of plasterboard so that anything you screw into the walls or ceiling will have a good grip, something plasterboard is not good for. If your budget is big enough, Green Glue will be worth considering.

bivis wrote:Source of the postSteel gague would be 7,5cm or even 10cm for stronger support

Again, Stuart will give you professional advice as it may depend on whether the booth's ceiling will rest its entire weight on the steel stud walls which will probably require the 10cm load-bearing studs or whether you will use ceiling isolation mounts so that the building's ceiling is bearing the weight of the booth ceiling and the walls can be ordinary 7,5cm studs.

If you want to see a room built with standard steel studs and ceiling isolation mounts plus OSB and fire-rated plasterboard, have a look at some of the photos of my studio, here.

A question for Stuart: if bivis wants a 5cm gap using 7.5 or 10cm wide studs, would inside-out walls and ceiling be realistic to construct in such a small space?

The ceiling could be suspended if it would be to heavy to sit on the new walls.
Any suggestion what to do with the floor?

Btw starlight, saw your build thread, awesome!!!