Where can I find....

[I-AM]

Good Day Homerecording gurus,

I know it has been a while since I have posted, but that is because there is so much information on this site, all I do is read and am usually able to find all my answers.
Which brings me to my question of the day. I have decided to build a vocal booth due to the way my old Central Florida condo has been made. Ya know, hard marble floors and walls that just echo, and echo, and echo, and echo, and....... Well I guess you get the point.
I am using this site http://www.digitalsynthologie.de/gesangskabine/index.html
as a reference for my booth, but I have scaled it down to 3.5'x4'x7'. On this site they say that they cemented the outside panels with Rockwoll Planarock for acoustic insulation. Since I don't speak fluent German, what the heck is this stuff and where can I find simular panels for my project. I am definately sure that it is used for added accoustic isolation and the blankets on top of that sounds-well I will give it a shot since this setup is only running me about 300-500 dollars.
Also with my dimensions, I am sure there will be some bass buildup, so I was also thinking of putting fiberglass enclosed in curtains or blankets underneath the booth like it states on the site, and some bass traps directly in either the front or rear corners of the booth.
If anyone knows what type of material board or panels is equal to rockwoll or where I could purchase a simular item it would greatly appreciated.

Thank You

 

[RICK FITZPATRICK]

Hello I-AM. Although I'm not absolutely sure, I'm guessing that since this product is made by a Rockwool manufacturer, it is PROBABLY the same as RIGID FIBERGLASS, only made from mineral wool instead of glass. Owens Corning 703 is a similar product, but don't take my word on that. Its just a guess, as I can't think of any other kind of product that it could be. Although, why they put it on the OUTSIDE is anyones guess, EXCEPT, since this is a homemade booth, maybe the designer figured that since this product is used for sound ABSORPTION as well as thermal insulation, it would absorb sound impinging on the exterior of the booth. Hmmmm.. well, IF, this is indeed RIGID ROCKWOOL, I've got some news for you. Insulation used in this manner, eventhough absorbing incident sound, will actually do very little for isolation. Insulation is used in MASS AIR MASS resonant assemblys to dampen the panels and is usually batt type insulation found in wall cavities.
I'm certainly no expert, but their description tells me something.

The isolation is very good. If you sing inside the booth you'll hear it very low on the outside. Behind the studio door outside the room you will hear nothing. Behind a wall you will hear less nothing. We use this booth to record day and night.

What the hell is "less nothing"? What this says is you will hear sound transmission IN THE ROOM that the vocal booth resides, and one room away you will hear "nothing", and outside of the studio you will hear "less nothing". Hahahahahaha! Ok, enough poking fun. The reality is..
The MDF panels provide "X" db of sound transmission loss. The walls to the an adjacent room provide "X" MORE db of loss, and beyond that you hear virtually nothing. What this ALSO says, is if you have a sound source in the same room as the vocal booth, you WILL HEAR IT IN THE BOOTH!! So will the mic.
So, this is what you must decide. IF you want this level of isolation, build it as shown. However, if you are in a city, and the room has exterior walls, you MAY hear environmental noise INSIDE the booth. Note, I say MAY. It depends on your particular environment. If on the otherhand you are recording mission critical recording, and would like a higher level of performance, let me know and I will tell you EXACTLY how to build it, although it will not be as simple as shown. High STL(sound transmission loss) performance partitions require TWO LEAF M-A-M assemblys, usually with the INTERIOR MASS(leaf) de-coupled from the exterior MASS.
And here is another little jewel. The "anachoic" looking FOAM wedges are virtually a joke, as far as the formed shape is concerned. This is why. Foam absorbers achieve their function by virtue of "resistance" to air molecule movement within the foam "cell connections", or as called "interstices" in fiberous materials such as Rockwool and Rigid fiberglass. The thickness of the material is directly related to the absorption coefficient by FREQUENCY BAND by virtue of wavelength. What this means is this. In theory, since air is the medium which carries the sound "wave", molecular particle movement velocity is ZERO but pressure is maximum at a boundary(the mdf wall), and is at its maximum velocity at 1/4 wavelength from the boundary. At 1000hz, the wavelength is about 1.13 feet long(frequency divided by speed of sound) divided by 4 equals about 3 3/8", which is about the thickness of the "wedges". However, since the shape is a pyramid in 2 dimensions, this means ONE HALF of the available material has been REMOVED!!! In essence, this means about a half of the abosoption in Sabines at 1khz has been also removed. Although the surface area has been increased via the shape, the reality is the performance has been REDUCED.
This is why I would bet almost everyone who understands this principle, would recommend the use of OC 703 rigid fiberglass panels in leu of the foam "wedges". IF you were to build a M-A-M assembly booth, the "A" stands for AIRGAP. Which is between the two leafs of mass. It is here that standard batt type insulation should be used, AND, the larger this airgap, the better the performance at low frequencys. It is on the INTERIOR face of the booth, that the RIGID FIBERGLASS(or mineral wool) panels should be placed. AND, because of the principle of "zero velocity" at a boundary, a 1/2" minimum airgap should ALSO be provided between the absorption panels and the booth walls. This will LOWER the frequency band of absorption.
Another area of interest is ventilation. In the description given at the link, they state that ventilation was NOT required. Let me enlighten you. That is BECAUSE they have LEAKS around the door!! And that is another cause of sound leakage, as even a 1/32" hole can negate a ton of work and money. Because of this, seals around a door are a MUST, if high STL performance is to be achieved. But be forwarned. "Soundproof" translates to "Airproof", which in this case means BREATHING!! Not to mention heat buildup from humans, equipment and lighting. Hence ventilation, which requires SUPPLY and RETURN registers, ducts, fans etc, all of which can provide a source for NOISE AND flanking paths for sound. Not to mention a few other things.
Like structural transmission should you NOT float the booth floor, OR weight, which can place point loads on structures not designed to handle it, like upper floors in a cheap apartment.
Well, hope this enlightens you to a few of the concerns I have with "high performance" vocal booth construction. Let me know if I can be of further assistance. If on the otherhand, all you need is "almost good enough", good luck with your project.
fitZ

BTW, my disclaimer. I ain't no stinking "guru"

 

[I-AM]

FITZ,

Check your PM and Thank You.

I-AM

 

[RICK FITZPATRICK]

Here is a "sample" plan. This is a .dwg converted to .gif so the clarity suffers during compression. When plotted, or viewed with an Autocad viewer, it is extremely clear. Your will recieve .dwg files for plotting. Of course, the plans will be detailed and dimensioned. This is for illustration only.
fitZ