Hi Marten. Please read the
forum rules for posting (click here). You seem to be missing a couple of things!
the floor and the walls were covered in cheap carpet to keep the noise bleed to a minimum.
Firstly, the carpet is NOT doing that. It is NOT reducing noise bleed
at all. I don't mean that it's not doing it well, or not doing it enough, or not doing it at the right frequencies: I mean that is simply is not reducing noise bleed in any way, form or manner. It just isn't. It is doing ZERO to reduce bleed. How do I know that? Because carpet is basically a thin porous absorber, in acoustical terms, and porous absorbers do NOT stop sound from getting in or out. They just don't. That's a very common misconception, but it is a myth. I wish I had a dollar for every person who has asked me "What foam should I put on my walls to stop the sound getting out?"! The answer is always the same: "None": Foam will not do that. Neither will carpet, shipping blankets, fiberglass insulation, gym mats, mattresses, curtains, or anything else similar. None of those can "stop noise bleed" through the walls, simply because that is not how acoustics works.
Think of it this way: In many ways, sound behaves similar to water. There are a lot of analogies with water that help to understand the principles of acoustics.
Carpet, foam, curtains, insulation and all other similar materials are basically like a sponge: The type of sponge you use in your kitchen or bathroom to mp up water that spilled some place you didn't want it. So obviously, sponges are good at soaking up spilled water! In the same way, all of those materials (foam, carpet, etc.) are good at soaking up "spilled" sound. They are very good at it. That's why we refer to them all as "porous absorbers": because they absorb spilled sound very much like a sponge absorbers spilled water. And we acousticians and studio designers use those types of materials inside studios for exactly that purpose: to "mop up spilled sound that went some place we didn't want it.
So far so good.
But now consider this: If you wanted to build an aquarium to keep your fish in, how well do you think it would work if you used sponge instead of glass to make the walls?
That's the situation you have: Your carpet-lined room is like an aquarium built out of sponge: the carpet does not stop sound bleeding out, any more than that sponge stops water bleeding out of the aquarium. The ONLY reason why your room is somewhat isolated, is because of the hard, solid building materials behind the carpet: the
real walls and floor. The carpet has no effect at all on sound getting in and out. So whoever decided to put carpet on the walls has no idea at all about acoustics, and whatever else he/she says can safely be ignored.
The problem is that people often see cinemas with the walls covered in carpet, and they also note that the movie sound is loud inside and quiet outside, so they illogically conclude that it must be the carpet that is stopping the sound. What they
don't see, is the
real acoustic isolation and treatment that is
behind the carpet: What they don't understand is that the carpet is purely cosmetic: it is only there to hide the real treatment going on behind it, and also because it is a great low-maintenance wall surface that looks nice. But it does NOTHING acoustically. In fact, the type of carpet used in most cinemas and studios is acoustically transparent! It is specifically designed to not stop the sound going through, as it needs to get to the treatment that is behind it.
So the carpet you see on cinema walls has nothing at all to do with stopping bleed.
So what does carpet really do to a studio? It makes it sound like crap! That's what it does. (Excuse my French...)
Here's what it does, in acoustic terms, as compared to simple, thin professional acoustic foam:
carpet-absorption-spectrum-RVBK-S01.jpg
That's from a test conducted by a very reputable acoustic laboratory. As you can see, what carpet does is basically to "suck the life out of the room". It does the exact
opposite of what most rooms need. small rooms need a huge amount of absorption in low frequencies (below about 200 Hz), some controlled absorption in the mid range (200 Hz to 2 kHz) but rolling off slowly, then no absorption at all in the high end (above 2 K). Carpet is the total, absolute, and complete inverse! It provides a LOT of absorption where none at all is need, and it it provides no absorption at all where lots is needed.
So basically carpet is not only useless for treating studios, it in fact makes things much, much worse.
It makes the room sound dull, muddy, lifeless, "thuddy", uncomfortable, honky, boomy, and a number of other not-so-good adjectives.
It destroys the room acoustics.
That graph above is for thick pile carpet: if yours is normal thin house carpet, then things are even worse...
So, here's the thing: The carpet has to go. If you want to make your room usable as a tracking room / rehearsal room, then the carpet MUST go. It is no use at all in there, and not only is it not helping, it is harming.
Unless there's a major, very important, life-shattering reason why it should remain in there (maybe it is holding the wall together, and without tithe building would fall down ?
), then the very best option is to take it all out, and start with an empty room.
If you can't do that for whatever reason, then your second option is to cover it all up.
This is were the trouble starts. Right now the room doesn't really have a nice recording sound for live drums and acoustic guitars.
Right! No doubt at all about that. It sounds pretty terrible even for having a conversation, and drums must sound downright awful in there.
However, in every tutorial we read or watch, the base rooms have hard floors and walls where they use acoustic treatments to absorb certain frequencies.
Yep! Exactly. There's a reason for that...
Our room is the opposite and is absorbing the heck out of all frequencies because it is covered in carpet.
Actually, is only absorbing the heck out of high frequencies, which is why the room sounds so disgusting. Human hearing is most sensitive in the range 2k t 8 k,peaking around 4k. That's the part of the spectrum that your ears and brain are most interested in, because that's where "clarity" is. Your room is killing clarity. But because the carpet does nothing to the mid range (the "honky", hollow, clunky part of the spectrum), you hear most of that. And because it also does nothing to the low end, you hear all the boomy, muddy, bass.
Now the guy in charge of the warehouse is okay with us changing some of the stuff in the room and maybe put a hardwood floor over the carpet,
Great! Start by doing that. More below...
but does not want us to take the carpet of off the walls or the floor.
Why? What purpose could he possibly have for keeping a terrible acoustic problem inside your room? Tell him he can make money by taking it off carefully and selling it on e-bay....
If he is worried that taking the carpet off will somehow "increase the bleed" though the walls, reducing isolation, then he need not worry about that at all: it wont' make any difference, since it isn't doing much isolation in any case!
The question then becomes what we CAN do with the room to improve the quality of the recordings.
There are some things you can do if you don't take of the carpet, but it mostly involves covering up the carpet! There will only be a little bit of carpet visible in the room, when the treatment is finished.
One of the long walls has a small but wide window about a meter (3 feet) from the corner. This window is 100x40CM (3x1,2ft). On that same wall there is also a door in the corner. The door is a standard sized door.
Excellent! Those are all good. They provide some reflection for the room. If it was not for those, the room would sound even worse than it does.
The ceiling is a dropped ceiling.
Take that out as well. It will do several things: it will increase the height of the acoustic ceiling for high frequencies, increase the room volume, and give you access to the area where you need to install lots of acoustic treatment. There's at least several cm of extra room up there, and all of that is useful.
From what we have gathered the last few months, it would be a good idea to put in a wooden floor.
Yes! The simplest would be to put down two layers of thick plywood or MDF (19mm), screwed together, then put down ordinary laminate flooring on a suitable underlay. that will give you a reasonably good floor.
Also we had the idea of putting up some wooden panels in the room to help reflections. Basically doing the opposite of what you normally would do,
Correct, but it's not just plain flat panels that you need: those would create unwanted flutter echo and reverberation problems. You need reflective panels that are also diffusive. More below...
but since we are complete rookies when it comes to studio design we would really appreciate some advice on what you guys would do.
When I design studios, I often design them on purpose with the same basic problem as you guys are experiencing, but done properly: I design some rooms with 100% coverage of porous absorption on the ceiling walls, but I DON'T do it with then carpet! I do it with thick acoustic absorption (at least 10cm thick) that absorbs well across the entire spectrum, not just the high end. The reason I do that is so that I start out with a "dead" but roughly neutral room, except for the floor, which I always leave highly reflective. I can then "liven up" the room by adding specific reflection, diffusion, and resonant devices as needed to get it where I want it to be. Each device is designed to deal with a specific part of the spectrum, in a specific part of the room. I add those one by one, incrementally, until the room response is where I want it to be. This is the approach that you guys will have to follow, if you do not take off the carpet.
The other approach is what you have already found on the internet: starting with a very "live" and reflective room, then slowly "killing" it until you get it the way you want it. Some acousticians do that, and most of the advice you find is for dealing with that situation, since that's what most normal house rooms are like: hard surfaces all around. But when I'm designing from the ground up, I prefer to go the other way: start dead and add life. I find that doing it the "start live and kill it" way creates problems that I don't want, and can avoid by going the other way.
So, you'll need to do this the way I normally do it anyway! But the big difference here (huge, massively big difference!) is that I start out with a room that is dead across most of the spectrum, roughly smooth and neutral, whereas you guys ares starting out with a room is only dead in the highs, selectively dead, and very uneven!
I start out with proper acoustic absorption that is about twenty times thicker that what you have, so I have twenty times less problems...
So first comes the question: How much money are you guys thinking of investing in the acoustic treatment of your room? If you only want to sped a couple of hundred dollars, then there are some basic things you can do, but not much. If you are prepared to spend a few thousand dollars, then your chances of success are much better!
So lets' get that out of the way first: What is your budget?
Second, what is your goal? If you want this room to sound sort of decent for doing hobby demo type tracking, just having making music for yourselves and your friends, then there's no problem with achieving that at low cost. If your goal is to be able to do good quality indie style recordings, then that's a bit harder and needs a bigger budget. If your goal is high quality commercial recordings, competing with other pro studios in your town / city / country, then that can also be done, but it's a lot harder, and a lot more money. And if your goal is to be the next Abbey road, then you better spend the money on psychological treatment instead, not acoustic treatment, but because you are crazy!
OK, so let's start with those two items: budget and goals. And if you wanted to start treatment already, go out and buy plenty of 19mm ( 3/4") plywood or OSB, cover the floor with two layers of that, screwed together, put suitable underlay on top of that, they lay some nice looking, thick (8mm or more) laminate flooring. That will already make a big difference to the room acoustics. It won't be enough, but it will be a start.
- Stuart -
