Voiceover Suite Vocal Booth

Hi Guys, I am writing from Vessel Studios in Liverpool, England. The facility is, to date, just a Film & Photographic studio with a large Cyc-Curve studio area and residents rooms. This has all been built by my business partner and I over the past 10 months. Our next project is to create a Voiceover Suite, in an attempt to bring all parts of the film-making process in-house. For anyone interested in seeing the work we have already done, take a look at http://www.liverpoolstudios.co.uk. It is based in a 190 square meter Warehouse unit in an industrial part of Liverpool's Docks. The picture attached shows the office units (it's a pic taken before completion, not normally that amount of mess around :D ), on top of which I plan to build the vocal booth. The control room will then be housed in the central room on the second floor. The sound levels, in terms of ambient noise, in the main space are pretty low. I measured while a car alarm was going off outside and my partner had music on in the office and the sound meter read on average 33dB. I then measured sound levels directly above the office whilst my partner was on the phone and still had music on, which averaged 47dB. I then went into the room that will be the control room and asked my partner to talk loudly in the main space. This also came in at an average of 47dB. On shoot days, there is a large, heavy duty blackout curtain that divides the space and provides great sound insulation so the level of ambient noise never really raises above 55dB. The vocal booth will be built on the Top Deck. The surface that it will be going onto is 4.52m x 2.19m which is constructed thus (from below going up): False ceiling (plasterboard) 6x2" Joists mounted on the back brick wall and supported by the front wall of the control room Rock Wool Insulation 12mm Sheet OSB Chip Board 12mm Sheet Ply The roof will be directly above the booth. This is a layered roof of steel/insulation/steel. Because of the booth's position, the ceiling will have to follow the slope of the roof. This also dictates the outside hight of the booth. The highest point will be 2.2m. The reason for this is to allow a fairly decent area in the space I have at full hight before the slope starts. There will be an exterior brick wall directly behind the booth. In order to avoid the entire back wall of the booth being in contact with the wall, I will attach a secondary frame to the wall to then attach the stud wall to. I have attached a simple Sketchup diagram of the structure I intend to build (sorry for the crudeness, first time user). The front wall is extended further than the booth itself for aesthetics. Having read about a few similar constructions as well as reading the various sections about construction on John's website I have decided to construct the booth using insulated staggered stud walls. Then to deaden the sound inside, given it's a pretty small space, I was going to create an interior timber frame on the stud walls, fill with Rockwool Insulation and cover with fabric. My budget is incredibly limited. We do, however, have a certain amount of timber and sheet materials left over from the rest of the build. My first question is, am I on the right tracks so far? Does the general shape I have drawn seem ok and will the interior insulation deaden the room without colouring the sound? Is 2.2m high enough (given that 176mm will be lost from that for the thickness of the wall & insulation. Is MDF a good alternative to plasterboard for the stud walls? We have loads of it left!! Please let me know if I have missed any crucial details! Bit baffled by it all at the moment! Thank you for your time! Jacob

Hi Jacob, and welcome to the forum! :) Just a few comments on your project:

The control room will then be housed in the central room on the second floor.

I guess you already know this, but building a studio on the second floor makes it much harder to isolate, for several reasons. So the question is, do you need good isolation? How much (in terms of decibels)?

I then measured sound levels directly above the office whilst my partner was on the phone and still had music on, which averaged 47dB. I then went into the room that will be the control room and asked my partner to talk loudly in the main space. This also came in at an average of 47dB. On shoot days, there is a large, heavy duty blackout curtain that divides the space and provides great sound insulation so the level of ambient noise never really raises above 55dB.

Those are not good ways of measuring isolation, and it sounds like you don't have much isolation right now. Loud speech is around 75 - 80dB, so if that is coming in at 47 dB on the other side of the wall, then you only have about 30 dB of isolation, which is low. That's about what a typical house wall gives you. Not enough for a serious studio. Most studio builders want at least 50 dB of isolation, and much more if they can get it. The blackout curtain might block some voice frequencies to a certain extent, but it won't do much for the typical loud music leves that you find in a control room.

False ceiling (plasterboard) 6x2" Joists mounted on the back brick wall and supported by the front wall of the control room Rock Wool Insulation 12mm Sheet OSB Chip Board 12mm Sheet Ply

To me, that sounds like a fully-coupled two-leaf system, which will not get you much isolation. Still around 30 dB, since it is fully coupled. To get good isolation, you do need to decouple the leaves. depending on a number of factors, that just doesn't sound very useful for an iso booth. Also, 12mm is too thin for good isolation, in general. You should only use 16mm panels. 12mm is too flexible, lacks mass, and has undesirable resonant characteristics.

The highest point will be 2.2m. The reason for this is to allow a fairly decent area in the space I have at full hight before the slope starts.

It is probably fine for a vocal booth, but on the small side. You have not yet allowed for acoustic treatment, HVAC, furniture (if any), mics, etc., so it might be a tight squeeze in there when you are done. To put it in perspective for you, I did a brief animation with a human figure in there, so you get a better idea of proportions: http://digistar.cl/Vessel-Studio/Vessel ... ough-1.avi

In order to avoid the entire back wall of the booth being in contact with the wall, I will attach a secondary frame to the wall to then attach the stud wall to.

That does not decouple the frame from the brick: If the first frame is coupled to the wall, and the second frame is coupled to the first, then the second frame is also coupled all the way through to the brick. Decoupling implies total, complete mechanical separation: nothing touching nothing. No hard connections at all.

Is MDF a good alternative to plasterboard for the stud walls? We have loads of it left!!

Yes, MDF is fine, provided that it is thick enough: At least 16mm (5/8"). No less than that.

My first question is, am I on the right tracks so far?

Basically, yes, but there are a few steps you have skipped! :) First, you should determine how much isolation you need for that booth, then design the plan based on that. Guessing is not a good way to go about it! :)

Does the general shape I have drawn seem ok

It looks like it will work, but it is a bit tight, due the angled ceiling and front wall. Can you straighten out that wall at all? Make the room more rectangular and less triangular? And bigger, too?

and will the interior insulation deaden the room without colouring the sound?

That depends on how you treat it! And "dead" is not a good idea for a vocal booth. "Dead" is unpleasant, unnatural, and tiring to work in. It would be better to aim for a more neutral sound, not too dead and not to live. So if you can afford more space, then it would be good to make the booth a bit bigger. You didn't mention the door, a possible window, or HVAC, and those are all critical aspects of vocal booths, so it would be good to know what your plans are there. - Stuart -