Directing bass frequencies and sound proofing? | John Sayers’ Recording Studio Design Forum archive

Hey guys :D I was directed to this forum by a Fractal Audio mate. So please excuse my limited knowledge. Well, here's the situation my band is possibly moving into a new place to practice. And it's in the middle of the woods for the most part. There is one neighbors cottage that's about 50 yards from the building we'll be using. The room is a huge hall (large wooden space) so re-soundproofing it isn't really a financial option. I was wondering if I could build a little enclosure out of drywall and Mass Loaded Vynil to surround the bass and guitar cabinet on 3 sides, basically to direct the majority of the bass frequencies and sound in one direction away from the neighbor towards the unoccupied woods. I was thinking if it was contained and directed at the source it might be possible to minimize noise in one direction? Would this work?

Hi "rsf1977". Please check the forum rules for posting: you seem to have forgotten something... :) Regarding your question:

I was wondering if I could build a little enclosure out of drywall ...

Well, yes you can, but not like that. You continued:

... out of drywall and Mass Loaded Vynil to surround the bass and guitar cabinet on 3 sides, basically to direct the majority of the bass frequencies and sound in one direction away from the neighbor towards the unoccupied woods.

Unfortunately a 3-sided enclosure will not work to contain or "redirect" low frequency sound, for the same reason that a 3-sided fish tank won't hold water: It all leaks out the open side, and once it is out, it just goes everywhere! Same with bass sound. Low frequency sound is not directional: It just ignores any objects that are smaller than it's own wavelength, "wrapping around" them, and expanding equally in all directions. Low E on a 4 string bass is around 41Hz. That has a wavelength of nearly 28 feet, so it will pretty much ignore any object smaller than 28 feet, and just wrap around it, then spread out like water hitting the floor as it runs out of your 3-sided aquarium. In order to "focus" bass energy like that, you'd need to build something at least 28 feet wide, 28 feet long, and 28 feet high... Not a realistic proposition. And even if you could do it with those dimensions, it would then resonate very loudly every time you hit a low E! Clearly, this is not the way to do it. So how do you make an aquarium that actually does hold water? Easy answer: you put glass on all six sides of it. That's what you need to do: you need to build what is called an "isolation booth" (or "iso booth"), which is basically just a large box that you put the bass cab in, along with bass player and his guitar too. Normally iso booths y are made with plain old drywall or plywood or something like that, on a stud frame, and are large enough to accommodate the person, instrument and equipment. Since you have lots of space, you can make it as big as you want, and put the whole band inside it, in which case it isn't really an iso booth any more, but more like a "live room". Regardless of how big you make it, the concept is simple: Build a rectangular stud frame on the floor, attach 5/8" drywall to one side of the frame for your walls, put joists across the top of all that and attach more 5/8" drywall for your ceiling. Seal everything totally air tight (including the door, and window if you have one), and you are done! Now you have good isolation. How much isolation depends on a number of things, but you can improve it by adding more layers of drywall, in various ways. There are ways of calculating how much isolation you need, and how you need to build to get it. You also need to add things like ventilation so you can breath in there, and electrical circuits for lights and to power the equipment, but that's the basic idea. By the way, forget the Mass Loaded Vinyl (MLV): There is no need for that. What you need to stop sound is mass, and lots of it. MLV is just very expensive mass! Sound waves rally don0t care how much you pay for the mass that stops them: all the see is mass, not price tags. So get cheap mass, such as plain old drywall, plywood, MDF, OSB, etc. You'll find many web sites on the internet that make magical claims for MLV and other materials that the want to sell you, but in reality the vast majority of that is pure hype: Mass is mass, and there are no magical materials that somehow make the laws of physics go away...

I was thinking if it was contained and directed at the source it might be possible to minimize noise in one direction? Would this work?

It will only work for high frequencies, not for lows: Maybe you can persuade your bass player to switch instruments, and take up the piccolo instead? :) Just kidding... - Stuart -