"mobile" sound isolation booth

Hello, It’s been a while since I posted on this forum. I’m a drummer student from Holland. I’m also interested in recording and mixing as well. I would like to have a sound isolation booth for practicing at home. I already read the information on this forum, the SAE recording manual, and information from other sources. Well, I understand that building a sound isolation booth isn’t an easy and cheap thing to do. It would be a waste of money and effort to build a permanent drum booth, because I will probably move to another place within two years. So the best option I have is to buy or build a mobile sound isolation booth. There is a company in Holland that offers these isolations booths. Their webpage is: http://www.esmono.nl (click in the upper left corner for English). These boots are very expensive, but do a great job. And they are moveable! Here are a few picture’s of these booths: They offer 3 solutions: A 50mm sound studio, a 80mm sound studio and a double wall sound studio. They have an average soundproofing value between 30 and 35 dB for the 50mm version, between 35 and 40 dB for the 80mm version and between 40 and 45 dB for the double wall version. You can find the exact graphical measurements on their website if you would like to see them. (they isolate the higher frequencies more than the lower of course). The booths consist of several panels put together with compressing tape between them (to achieve a airtight seal). They have some kind of insulation on the ground. On top of that they put an U-profile where the vertical panels are held in place. When all the vertical panels are up, they put on the room in between the vertical panels. The roof panels are the same as the vertical panels. The roof panels "hang" in between the vertical panels with another profile. Again, all the panels are put together with the compressing tape to create an airtight boot. There are some "special" panels, e.g. a door or window or ventilation panel. These are basically the same panels. Some pictures: I have seen these booth's in real life and according the information I got from the manufacturer and owners I can tell that the panels are consisting of 1,5mm plate steel, insulation, black cloth and 1mm perforated plate steel (from the outside to the inside). Depending on the version you'll have a 50mm or 80mm panel. The double wall studio has two walls of 50mm panels with a 45mm air buffer between the panels. Here is a picture with a section I made of the 80mm panel as Esmono makes them: These booths are very expensive (even the used ones!). So I'm thinking of copying these booths and create one myself. So when I leave home I could bring the booth with me! Plate steel is a very expensive product and it is also very hard to work with. You’ll need special tools to fabricate it. So my idea is to build these panels using 9mm wood (MDF or plywood, which one would be better?) instead of the 1,5mm plate steel that forms the panel “box”. This is the only change I would like to make in the design. I would like to stay as close to the original design, as they have proven to work. Here’s a picture with a section of a panel using 9mm wood instead of 1,5mm plate steel. There are three things I would like to achieve: 1. Have enough sound isolation to not disturb the neighbours. A "real" Esmono booth would do the job, so mathematically speaking I need around 40dB of isolation. The questions remains how my "wood" version of the panels affects the overall sound isolation. 2. The possibility to take this booth apart easily and set it up elsewhere. Also, if I stay close to the design of the "real" Esmono booth things shouldn't be a problem. 3. Have a "dry" sound inside the booth. Again, if I stay close to the real booth (the Esmono booths have these perforated steelplates on the inside), this should not be a problem. Summing up: Actually I want to build a Esmono booth but replace the 1,5mm plate steel that forms the "panel-box" with wood. So here are my questions: - Does anyone have experience in creating a moveable isolation booth (somewhat similar to the ones I describe)? - Any ideas on how the wood (instead of the steel) will affect sound isolation values? - Any other recommendations/ideas/comments? Thank you!

Hi "rikplo", and welcome! There are several issues with your plan. First is that you seem to be ignoring density and mass. Steel is roughly ten times more dense than MDF, so you'd need 15 mm of MDF to get the same mass as 1.5mm of steel. Then, you say you want to stay close to the original design, but the original design is 1.5mm steel, not 9mm MDF! Simply changing the material from steel to MDF is a major departure from the original design, and in reality nobody knows if it will perform the same or not: you'd have to build a room and test it in an acoustic facility find out. Even using 15mm MDF is no guarantee that it will work the same way, since MDF is very different from steel not just in mass, but also in terms of rigidity (stiffness) and natural resonant frequency, for example.

have these perforated steelplates on the inside...

There's another issue: perforated metal panel is acoustic treatment. To get the same effect as the manufactured booth, you'd have to use the same thickness of panel with the same diameter holes and the same coverage (number holes per square foot). Change any of those, and you change the effect.

The questions remains how my "wood" version of the panels affects the overall sound isolation.

Mass law says that 9mm MDF should give you roughly thirty-something dB of transmission loss at 125 Hz, rising to roughly forty-something db TL at 4 kHz. For 15 mm MDF it would be about 3 or 4 dB better across the scale. Since this would just be a single-leaf system, it's basically a straight line, so figuring STC would be easy, if you wanted to do that. So your plan might work, provided that you use at least 15mm MDF (9mm would be too flimsy, too flexible, and not massive enough anyway), and the exact same perf panel. If you seal it well, you should get close to the mass law prediction. I would use plywood instead of MDF, though. It is tougher, and stands up to impact and rough handling much better. The final point is that you say you are a drummer, and drums are pretty much the loudest of all acoustic instruments. You can easily put out 115 dB, and even more if you try hard. With 40 dB of isolation, that would give you a level of 75 dB outside, which is still pretty loud! Most of that would be in the low frequencies, which are hard to stop anyway, and give the unknown resonant nature of your MDF box construction, the total isolation might not be as good what you are expecting. Having said that, there are a couple of examples here on the forum of designs for "movable" booths that might work for you, but if you need high levels of isolation, then there are other ways of accomplishing that. The only problem is that they aren't very portable! But you could probably still build something that can be bolted together and dis-assembled if you ever move, if you plan it carefully. - Stuart -

Soundman2020 wrote:

Hi "rikplo", and welcome! ... - Stuart -

Hello Stuart, Thank you for your helpful reply! So the issue's you mention are: - Use plywood instead of MDF. Check! - Mass / density - Rigidity - Natural Resonation So, I've searched after some statistics and you're absolutely right! :D The weight of steel is 7800 kg/m3 and the weight of plywood is between 700 and 800 kg/m3. So, as you already estimated, you'll need 10 times thicker material to have the same amount of mass. Let's assume we use 18mm plywood... (because 15mm is a little bit more uncommon, so little bit harder to get, and as a bonus, 18mm adds just a little bit more mass) This would eliminate the "mass-problem". That leaves us with rigidity and natural resonation, which are much harder to determine. I'll try to find more information on these issue's, but I am wondering how much of influence the could have on the sound isolation of the construction. The inside perforated panel stays the same as the orginal design, 1mm perforated steel. I tried to find some more information on portable booths and fortunately I found 2 other company's who make kind of the same products. One of them (Meyer Noise Control, webpage:http://www.meyernoisecontrol.nl/index2.eng.php) had some drawings on their website. The panels are kind of the same as the Esmono panels, except for the 15mm gypsium board the glued in to the panel. So I thought of using the orginal Esmono panel, replacing the 1,5mm steel with 18mm plywood, and adding a 15mm plasterboard on the inside. Also, because of the "loss" of insulation space as a consequence of using thicker materials, stretching the panel to 94mm instead of the original 80mm (assuming that a thicker panel would only increase the sound isolation). This gives you a panel that looks like this: - 1mm perforated plate steel - black cloth - 60mm of hard pressed rockwool - 15mm plasterboard - 18mm plywood Well I just skipped the possible natural frequency and rigidity differences between steel and plywood, but apart from those possible differences, what do you people think? Thanks so far!