Basement design

Hi all - great site, lots of good ideas here. Background: I've played drums for ~30 years semi-professionally and work on a variety of part-time projects. We're in early stages of new residential home build in Maryland (US) and I would like to create open basement space that mixes rehearsal area with ability to play live for small audiences and potential for some live tracking. Kids are older middle-school and play a variety of instruments, so secondary goal is create welcoming space for them to invite friends over to play. Here's one example: http://www.houzz.com/photos/720050/When ... room-miami Good news is that we're in architecture phase now so all options are open, budget is reasonably flexible, and current basement plans have a space that is pretty well insulated on five out of six sides (19'x19'x9' space under garage with 4" concrete floor, steel pan above supporting concrete garage, and poured concrete for 3 walls). Bad news is I play drums and the two primary goals of the project 1) sound-control for rehearsal and 2) 'open' space are a bit at odds . . . Question (first of likely many as this project progresses :D ) - Are there products that would allow 'reasonable' sound control to enclose rehearsal space and also allow it to open to rest of basement? (I know 'reasonable' needs to be better defined and I'm happy to take some measurements - in a previous house I had a similar room, enclosed on 5 sides by concrete, and a single interior door to rest of basement with much smaller wall space ~3' and lining with acoustic foam on the inside was sufficient to hear NO drum impact upstairs, in my current house an unfinished larger basement space allows pretty good drum and bass fidelity throughout much of the house. - Unconventional options might be something like a single panel over and up garage door with insulated glass or a movable room divider (like at conferences) - I realize these options will not be optimal for sound-mitigation but might be sufficient for dual-purpose nature of the room - More conventional might be shrink rehearsal space (~19'x12') with room-within-room construction to ensure sound reduction and create open stage space outside of this room OR explore room-within-room for the entire larger basement space (adding ~50'x22' area to the 19'x19' under the garage). Thanks in advance for your thoughts. Jim

Some noise data: Local noise ordinance is 65 dB day, 55 dB night (a-weighted) measured at receiving property line Drums can get to max 110 dB measured next to snare (hitting louder than I typically play), typical volume of rehearsal is ~80 dB measured outside basement door (interior hollow door with typical gaps), ~70 dB measured from kitchen directly above unfinished basement, and music can be heard outside the house but doesn't move the needle on the lowest 60 dB setting.

Hi Jim, and welcome to the forum! :)

I would like to create open basement space that mixes rehearsal area with ability to play live for small audiences and potential for some live tracking.

OK, so it's basically a very large live room, with a small control room? Is that the general idea?

pretty well insulated on five out of six sides (19'x19'x9' space under garage with 4" concrete floor, steel pan above supporting concrete garage, and poured concrete for 3 walls).

Nice! Great start. But what's on the "sixth side"?

Bad news is I play drums and the two primary goals of the project 1) sound-control for rehearsal and 2) 'open' space are a bit at odds . . .

Not really. You can have both. Isolation is one thing, and treatment is another totally different and unrelated thing. So it is possible to have a room that sounds great but isn't isolated at all, and it is possible to have a room that is amazingly isolated but sounds like garbage. There's very little relationship between those two aspects of acoustics. It is also possible to have a room that sucks in isolation and sucks in the way it sounds too! And your goal is the forth possibility: well isolated, and also sounds good. Your room can be both large and well isolated. It can sound good inside and also sound silent outside. The two goals are not really at odds with each other. So, taking "loud drums" as the basis, that gives the answer to one of the two most critical question, basic questions about your studio: "How loud are you?". Answer: In excess of 115 dBC. Now you need to provide an answer to the other question: "How quiet do you need to be?". You already answered that partially, with your second post, but 55 dB is just the legal limit, that should keep the cops away from shutting you down. However, there's also the "WAF" and "NAF" issues to consider: "WAF" is "Wife Acceptance Factor" and NAF is the "Neighbor Acceptance Factor". It's one thing to meet the legal side of things, but another to keep good family relations and good neighbor relations, so it would be an excellent idea to ask them what they think about what constitutes "quiet" and "not quiet", with your sound level meter in hand, so you can put a number to their opinion.

Drums can get to max 110 dB measured next to snare (hitting louder than I typically play), typical volume of rehearsal is ~80 dB measured outside basement door (interior hollow door with typical gaps), ~70 dB measured from kitchen directly above unfinished basement, and music can be heard outside the house but doesn't move the needle on the lowest 60 dB setting.

All of that is way on the low side, probably because you are using "A" weighting and "Fast" response. Set your meter to "C" and "Slow" to get realistic readings. Yes, legal limits are usually specified "A", but that's not realistic. "A" weighting is fine for low typical level sounds, such as speech and ordinary household sounds, but not for studios. "A" does not consider low frequencies. "C" weighting is a much better representation of the way people actually perceive loud sounds, since it gives more emphasis to the low end, which is what is most annoying late at night. So re-check your measurements with "C-Slow", and I'm betting you see an increase of 5 to 10 dB on all of those.

- Are there products that would allow 'reasonable' sound control to enclose rehearsal space and also allow it to open to rest of basement?

It's not so much "products" as "design". Plain old comm ordinary building materials, such as drywall, studs and pink fluffy insulation, can be used to get high levels of isolation, if used correctly, and even the most-expensive best-hyped "soundproofing" products can give terrible isolation, if not used correctly. Let me explain: First, that thing about the difference between isolation and treatment: Isolation just means "stopping sound from getting from "A" to "B". You can't actually stop sound completely, of course: no conceivable barrier can prevent a sufficiently loud sound from getting through, so true "soundproofing" is impossible. But you sure can make it really hard for the sound to get there, and decrease the level substantially! I'm sure you already know that sound is just "vibrations in the air", or pressure variations, to be more technically correct. And when those vibrations hit any material object, they transfer energy to it, and make it vibrate at the same rate. Which in turn means that the OTHER side of the object also vibrates, transferring the energy back into the air again, and hence the object has not stopped the sound from getting through. That's the problem with typical house walls. It turns out that there really aren't many ways of actually stopping sound, according to physics. The first thing you can do is to make that barrier so rigid and stiff that the sound waves cannot make it vibrate in the first place. Unfortunately, there are no such materials available on planet earth: Even solid bedrock isn't rigid enough to do that. That's why earthquakes can be felt hundreds of km away: the rock transmits the vibrations. The second thing you can do, is to make the barrier so massive (heavy) that the sound waves cannot make it vibrate. Once again, there are no such materials. Once again, earthquakes are the perfect example: even the entire planet isn't massive enough to stop them! The third thing you can do is to "decouple": take away all possible paths that the vibration could follow between "A" and "B". That also includes taking away the air, since sound travels pretty well through air. So if you can persuade NASA to let you build your studio on the moon or the ISS, you'll be fine! :) Otherwise, no luck. There's a final option: "damping". You can sort of make the sound wave move through molasses, bog it down, so it "runs out of steam". You do that by putting fibrous things in its way, such as fluffy insulation. But you need an awful lot of "molasses" to fully damp a sound wave down to nothing! Huge amounts. Out of the question, for any realistic studio. And that's about it. There are no more options: Mass, stiffness, decoupling, damping. There are no other mechanisms for stopping sound. And none of these four are very good.... by themselves... ! But it turns out there's another option: by combining all of the above in certain ways, you can really have a huge effect. For example, if you set up two "leaves" of reasonably massive, rigid surfaces (such as drywall), so that they are not connected to each other (decoupled), then put some damping between them (such as fluffy insulation), you have an excellent barrier that really does a great job at stopping sound from getting out of your room. Such as, for example, two sheets of drywall on separate stud frames, with only an air gap between them, and insulation in the air gap. Bingo! It works because it is a tuned filter, sort of like a parametric equalizer on your console or DAW: it is a bandpass filter, tuned to one specific frequency, which it allows to pass really well, but it actively resists all other frequencies. So if you tune it right, such that the only "band" that it "passes" is subsonic, then it does a darn good job of isolating all sonic sounds. That's a "fully decoupled two-leaf MAM" wall, in technical jargon, and it isolates very well. Done right, it can isolate at levels of 50, 60, 70 even 100 dB: It stops a lot of sound from getting out. So no single "product" by itself is any good at soundproofing a room ("isolating" it), but the correct combination of materials and techniques can get you major isolation. HOWEVER! (You just knew there was a catch, right?) Here's the hitch: if the walls stop sound from getting out of your room, then obviously the sound stays in the room! It can't go anywhere else, so it must still be inside the room. The walls cannot destroy the sound: they just bounce it back, so it stays in the room, bouncing around all over the place, making the room sound bad. That is called "reverberation". It is what you hear in an empty room with no furniture, nothing but the bare walls, floor and ceiling around you: Ugly! The room sounds bad because the sound stays in, reverberating around between the walls. The better the walls are at isolating, then worse the room sounds inside. If you think about it, the exact opposite of a room is open air: if you set up your sound system in the middle of an empty field, with no trees, buildings, or anything else around, then it sounds great, because no sound ever comes back to you: you hear the speakers, pure and clear, with no room to affect them at all. They sound just the way the manufacturer intended, and you'll have the best possible sound from those speakers, coming directly at your ears, not muddied by any reflections, reverberation, or any other artifacts caused by the room. OK, so those are the two extremes: 1) a "room" that does not isolate at all, allows all of the sound to escape, none of it comes back, and sounds great. 2) A room that is highly isolated reflects back ALL of the sound, and sounds terrible. That's where treatment comes in: since a well isolated room sounds terrible, the purpose of treatment is to make it sound good again. The idea is to control the reverberation, reflections, etc. so that the room itself does not add anything to the sound, nor subtract anything from the sound. It should be neutral, flat, "not there". It should not "color" the sound. And just like for isolation, it turns out that there are only a limited number of options available for accomplishing that. You can absorb some of the sound, you can diffuse the sound, you can reflect it, you can diffract it, you can force it to cancel itself out, and that's about it. So basically your options are absorbers, diffusers, reflectors, diffractors, and resonators. There's not much else you can do. Diffraction isn't much use, and is really hard to do. Resonators are a major pain to get right. Diffusers are not suitable for small rooms, for reasons too complex to go into here. Reflection is part of the problem! That leaves, basically, absorption. That's why you see that so much of the treatment in small rooms is based around very large amounts of fluffy insulation, since it is really good at absorbing sound at low cost. Yes, you do also see some forms of resonator, and most studios also use some form of diffusion, and some type of angled reflection to send the sound waves away from places where you don't want them, and towards absorption, but the main active ingredient in treatment is plain old simple absorption. That's the same "make it move through molasses" concept as above. As sound waves move through the fibers of insulation, they make the fibers move just a little, vibrating microscopically, and that robs the sound wave of just a bit of acoustic energy. The fibers turn the acoustic energy into low-grade heat, so it is no longer sound. Each fiber only takes out an infinitesimal amount of energy, but if you have enough fibers of the right type ("billions and billions"), you can make a big dent. So absorbers are usually large, and they are usually deep. They have to be, to have enough effect. So, by putting the right type, thickness and size of absorbers in the right place, aided by reflectors, diffusers and resonators, you can get the sound under control again, and make the room sound less bad. So that's basically it: Isolation stops sound leaving, keeping it inside, making the room sound bad. Treatment makes it sound good again. Of course, it's not quite that simple, but that's the basic concept. Isolation can also be part of treatment, and treatment can affect isolation, but it helps to think of the two as independent, separate and even opposite things. Isolation is done with hard, solid, massive, rigid things, treatment is done with soft, flexible, fluffy, light things. (Once again, not really exact, but a good concept). Not sure if that helps, or just totally confuses the hell out of you! :)

- Unconventional options might be something like a single panel over and up garage door with insulated glass or a movable room divider (like at conferences) - I realize these options will not be optimal for sound-mitigation but might be sufficient for dual-purpose nature of the room

The problem with must "unconventional" acoustic treatment is that it has already been thought of, tested, and discarded as an option by researchers! The ones that were thought of, tested, and accepted are the "conventional" ones, because they work. That's not to say that nobody can ever come up with a new way of isolating of treating, but whatever "new way" they come up with will still have to follow the laws of physics that govern the entire universe, and those are reasonably well understand, in relation to the science of acoustics. There are unconventional designs that work but are impractical for one or other reason (cost, size, weight, etc), and there are also unconventional ones that don't work. And of course, there are more than just a few "unconventional" treatments that are just plain old snake-oil! If it sounds too good to be true, then it most likely is. There are no "magical" materials that bypass the laws of physics. Anyway, the second one of your options (moveable room divider) really is a possibility, since as you noted they do work at conference facilities. But the cost of doing that right for a basement might be drastically higher than you intended. Conference facilities don't mind paying big dollar amounts with lots of zeros on the end for isolation partitions, since they will recover their investment from renting out the rooms at high prices. But that option might not be in the cards for you. There's also the issue of "what" those movable partitions are able to isolate: they are NOT designed to have a full rock band on one side and sleeping babies on the other! They are designed for typical conferences: people talking. It is one thing to isolate speech, even loud speech for a PA system, but entirely another thing to isolate drums, bass, keyboards and guitars. Low frequencies are the hardest of all to isolate, and "low frequencies" is what most modern music is all about. Isolation is much less effective at low frequencies than at mids and highs. The effectiveness of isolation drops by at least 6 dB for each octave you go down the musical scale: simple law of physics.

- More conventional might be ... room-within-room construction to ensure sound reduction

Exactly! That is, indeed, the best way to isolate a room when you need high levels of isolation: Just build a fully decoupled two-leaf MSM system, which is more commonly known as "room-in-a-room", and tune the walls to resonate at no more than half the lowest frequency you need to isolate. That's a tried, tested, proven, conventional design that has been shown to work in numerous laboratory tests, and even more numerous buildings, all around the world. It is the way the majority of studios are built these days, because it works, the science is understood, the equations are simple, and it also turns out to be the least expensive way of doing it. After all, if any of the those much-hyped "magical" products or snake-oil based unconventional systems actually worked in reality, while also being cheaper and more effective, I rather think that studio designers and owners would have adopted them by now! :) - Stuart -