Getting ready to design and build a vocal booth.

[Eugene1973]

Hi, I have a home studio mixing room in my house. It is treated and fine for mixing and laying down instrument tracks via DI but not for critical microphone recording of instruments/vocals during the day, though it is quiet enough at night. However, I intend building a soundproof booth in another building beside the house so I can track with microphones at any time. The building is used by me for many purposes and is about 30-40 meters from a main road. My biggest problem here is rumble from trucks passing by, I can hear the low freq rumble from them while inside this building.

This will not be a fancy studio build and may be temporary. It just needs to be functional with the greatest amount of sound isolation possible from the exterior surroundings, i.e I want as little bleed in or out of the booth. I may try to design this to be modular so I can remove it and rebuild it perhaps.

The exterior walls of the building are 15' tall and there are two main levels and a partial 3rd floor loft. The perimeter of the building is 32 'x 26' and is built with 6" concrete blocks. The bottom storey has a concrete floor and the walls are plastered inside but not on the outside yet. The upper storey floor is constructed from 3/4 inch chipboard flooring sheets mounted on wooden 6" x 2" joists. These joists are braced and their ends fixed into the exterior concrete walls to take the weight of the floor. The span is further supported halfway across by a load bearing steel girder running horizontally from wall to wall perpendicular to the direction of the joists. The upper level is also plastered on the inside.

The bottom of this 1st storey floor is open in that you can see the joists when you look up while downstairs, no sheeting or rockwool was used. Both floors are linked by an internal wooden staircase at the side of the building. Chipboard is called particle board in US. I have re-amped guitar parts in this building before using a mobile location recording rig and an isolation enclosure I built for recording guitar cabs.

On the 1st floor there is already a section of the 32'x26' floor space sectioned off with a wooden stud wall construction my father put in years ago. It is in this partitioned off stud wall area I intend to put the booth as it can be heated easy. There is an area of W 3.9' x L 7' x H 6.7' I can use for now.These wall studs are 4x2"s I believe and I seem to remember that he lined between the vertical studs with fiberglass rolls or some such. Where the studs form dividing walls both sides are sheeted with 1/4" textured hardboard. The ceiling was again constructed of 6x2" joists sheeted with 1/4" hardboard on the underside and 3/4" chipboard on top, again I think insulated with fiberglass roll again. This upper 3/4" sheeting forms the upper 3rd floor area or loft but there is no footfall up there.

I can do two things here and either way I will not use the ceiling of the existing stud partitioned area as the ceiling for the booth. I will build a ceiling under the main ceiling to further isolate for sound transmission but will enhance the sound insulating properties of the main ceiling directly over and around the booth's ceiling to give it the best chance.

Two of the existing stud walls form an L or a corner which I could improve by removing the hardboard sheeting both sides and packing between the studs with rockwool and fitting 1'' or 3/4'' plasterboard or Gyproc Soundbloc direct to the studs or by means of a stud isolators that the gyp sheets fix to. I would do similar to the ceiling. Then I could form the other half of the booth by fixing new stud wall and using the same system. I can design it so that there is a single door into the booth at a 45 degree angle rather than having 4 x 90 degree corners, or build a sound lock with two sequential doors but these would mean the booth would be rectangle shaped (no other choice here) any corners will be filled with a system I developed for bass traps in the studio in the house that works great. The other thing I can do is build a room within this partitioned off structure but I only have 3.9 foot width to play with here, which is tight enough and the stud walls when installed are going to make the inner booth dimensions smaller if you get me.

Some of these joint sealants made for soundproofing are crazy expensive so I will research alternatives and see if I can find a cheaper alternative that works well. I have a way to test it in fact between two rooms in the house, if I can hear the tv next door in the adjoining room the sealant is not up to the job. I can experiment till I find one that works at a good price point.

The following are the things I am wondering:

1) If I do build my booth as a room within a room inside my existing upstairs partitioned stud wall area do I float the walls of the booth but not the floor?

My existing 1st storey 6x2 stud sheeted floor is strong so I could line the booth floor with two layers of soundbloc and a few additional layers of various insulating materials to decouple the floor from the main floor as much as possible. Various materials work well at different frequencies so you need to tailor to your needs, in my case low end rumble mostly. I can run a series of tests out there to show what problem frequencies I have to worry about. I have a special flat response mic for that job and I can run a frequency Spectrum analyser at various times over a series of days / nights to get a more informed look at materials I need to make my various sound barrier layers so I can choose the combinations correctly.

2) The area of the main floor my booth's floor can be built on - do I line between the joists underneath with rockwool and fix a layer of 3/4 soundbloc sheet to the underside to further sound insulate? Some of you state it can resonate.



I use the Universal Audio 'Oceanway' plugin which more or less allows me to 'lift' my take and re-model it's mic choice, placement and the actual simulation of the live room space it was recorded in all in the digital domain to match the sound of the rooms at Oceanway Studios. It works very well and I have achieved great results with Piezo recorded DI acoustic tracks this way. More or less I move my take into their room. It works great. I am not saying it sounds exactly the same (I have never tracked there) but it works stellar. So, if my booth is dead sounding it doesn't really matter I have ways around this. The main objective here is to soundproof my booth as much as possible to stop my mic picking up unwanted noise from outside.However, I do rather setup my takes in advance of recording to get the best results possible. I use a system in the studio that allows me to change how absorbent or reflective the walls/floor/ceiling are prior to recording. I will use a similar system in the booth if space allows, this may enable me to track acoustic instruments in there if I can't wait for the house to quiet down and record at night in the studio. I use an L22 mic too which is great in post production.

So, do I float the booth's walls but not the booth floor as described? As someone suggested somewhere, I could build my booth floor in a sand pit structure possibly too.

So, what do you guys reckon?

[gullfo]

if the floor on the 1st floor is solid, then float the entire booth - you have plenty of room so consider making the booth using 3x 5/8" drywall over 3/4" plywood (inside out so the interior frame hold the insulation and cloth)
you didn't mention how large the booth would be but of course larger tends to be better even for vocals. depending on the budget, you might go as large as 7x11 feet. float the entire unit on proper isolation pads. also, if you have a sand pit, it might be an option to mount it on blocks in the sand pit although your still susceptible to the rumbling once compress. so the proper isolators would ensure only the very lowest frequencies would make it through and you could then just filter those.

[Eugene1973]

if the floor on the 1st floor is solid, then float the entire booth - you have plenty of room so consider making the booth using 3x 5/8" drywall over 3/4" plywood (inside out so the interior frame hold the insulation and cloth)
you didn't mention how large the booth would be but of course larger tends to be better even for vocals. depending on the budget, you might go as large as 7x11 feet. float the entire unit on proper isolation pads. also, if you have a sand pit, it might be an option to mount it on blocks in the sand pit although your still susceptible to the rumbling once compress. so the proper isolators would ensure only the very lowest frequencies would make it through and you could then just filter those.

Hi Glenn, yes the main floor on the 1st storey is 3/4" chipboard sheets nailed to the 6x2 joists underneath and they are all bridged to each other for strength. My father was an architect and builder and I remember putting in that wooden floor structure with him at the time. It is a very rigid. To float the entire thing I would end up with a room about W3' x L7' x H6'. This will probably be a temporary booth for now until I get more time to do a better job later which will take more planning and reconstruction out there, but for now I need to get a booth up to get some work done quickly.

I think what you mean is from inside booth wall to outside - plywood or MDF or chipboard nailed to stud, rockwool between vertical studs and the 3 x 5/8 gyp sheets fixed to the outer side of the stud yes? I can add a few other membranes perhaps too.

I was researching those Auralex U boat joist floaters but read in forums that a lot of people were saying not to float the booth as the floor would be resonant and possibly make things worse. They look like a good product though and lots seem to use them. I can get them in Germany.

What do you reckon about packing rockwool between the joists of the main floor under the booth and capping that area with a sheet of Soundbloc?

Thanks for your reply Glenn.

[gullfo]

i would agree with other comment made - the framed floor would not be a good choice for floating. then again, you could build the isobooth, then jack it up onto isolators and see if there is a positive difference. or start with isolators and remove if they're not effective. in this case, empirical testing will be more effective than theory
i'd suggest - if it's an option - to make the booth bigger rather than smaller - for 4' W. height should be taller if possible also.

[Eugene1973]

i would agree with other comment made - the framed floor would not be a good choice for floating. then again, you could build the isobooth, then jack it up onto isolators and see if there is a positive difference. or start with isolators and remove if they're not effective. in this case, empirical testing will be more effective than theory
i'd suggest - if it's an option - to make the booth bigger rather than smaller - for 4' W. height should be taller if possible also.

Yes, the ears will tell all at the end of the day. It will actually be possible to do an A/B test with/without the floaters.

What I have decided to do is remove the existing stud partitions altogether. They were built for a different purpose and working around what is already there is restricting me too much. I will remove all and design from the ground up with no restrictions. I have figured out what I am going to do now and I will have approx. 9'x7' floor area to play with for now.