Absorbing Room - materials, their shapes, what's the difference?

Question

Internet is really lacking information about acoustics in the room, absorbing materials, it's shapes and patterns.. how to glue them, why there are different shapes.

I really would like to know how to make a simple recording room at your house. Mostly I'm planning to have a DAW table. I want to remove echo from my room. And I have woody door which is kind off.. really thick so maybe some solution to isolate them..? Because I'm not alone living in flat =) + I want to record vocal in this room, and I already ordered a filter for (around) mic

So question basically is:

• What kind of materials do exists out there (woody, foam), and what are they for..
• Why there are many shapes of foam? for example if i have this material over whole wall, and mixed shape of this or this material covered in chess style over whole wall.. what's the difference?
• Why does monitor speakers should be on speaker-pads.. why it's useful?
• What's the best way to glue absorb foam to the walls, without damaging them? everybody uses some kind of spray... and there are plenty of them on sale... what's the difference between them?
• If all room will be covered with foam how about the air..? I heard it will be really dry, how to handle/avoid this..?

Any theory/practices and links are welcome!

Answer 1

A good reference on this subject can be found in Master Handbook of Acoustics by F. Alton Everest. The various shapes of acoustic foam are more for aesthetic reasons than acoustic. The contours may have marginal benefit in diffusing the sound field by means of acoustic refraction. The more complex the sound field of your room, the more "open" it will sound. Adding too much absorption will cause your room to sound small and unpleasant. You want to maintain sufficient reverberation time (a measurement known as RT60) for your room's purpose (mixing, recording, live playing, et cetera). The book above discusses this, but you might want to check out the room mode calculators linked below. At least one of them will give you estimated RT60 values for your room and how much absorption you need to add (in Sabins) to reach that number. Note that 2" foam has virtually no impact on frequencies below 125Hz which is where most small rooms need treatment the most. The calculators will help tell you where your expected problem areas will be but nothing beats in-room measurements with a Real Time Analyzer. Acoustic materials should be strategically applied to optimize the sound field at the mixing desk. This often involves a live-end dead-end approach to the room, but there are conflicting philosophies here as well.

Bob Gold's Room Mode Calculator, you might also try searching for "Mark Wieczorek's Room Mode Standing Wave Calculator", I would provide the link but I'm limited to two as a noob.

Good luck on your project.

Answer 2

Everett's Acoustics is indeed strong; however, a few caveats

First, Everett's book is unmanageable without at least a basic grasp of electronics. As a first-year electronics major, I would say I understand about 50% of it.

Second, Everett's book is haphazard. One or two chapters are devoted exclusively to software simulation, which is near-useless for anybody but professional consulting firms (who incidentally have no need for his book).

To solve your problem, answer some basic questions

1) Do you want to record and mix in the same room? Hint: not if you can help it. Mixing booths and recording rooms have entirely different requirements. For most purposes, you want your recording space to be as dead as you can make it. By dead, I mean that the walls should reflect as little sound as possible back into the room, instead absorbing asmuch sound as possible. A mixing room should be dead in front and live in back. If you only have one room to work with, deaden the walls and mix with headphones.

2) What can you afford? Really low budget will have to do with lots of rugs and curtains. IF YOU HAVE WINDOWS COVER THEM WITH HEAVY CURTAINS.

3) What are your room problem modes? Yes, the calculator is good, but the only way to truly evaluate a room is via pink noise test. To do this, you need a halfway-decent speaker and a halfway-decent mic. Use the speaker to play pink noise and the mic to record it. Use the deviations from the standard mic response and the standard speaker response to identify your problems.

Answer 3

There are a lot of questions in there, so you may be better off posting them as separate questions...

but here goes anyway:

Acoustic foam is probably the easiest thing to remove echoes from a normal room - it's also simple to remove if your needs change

For cost saving purposes you may not want to cover the whole wall, so interspersing shapes will at least give you decent cancellation. Having shaped pieces in the corners to kill off resonance there can be very effective

Speaker pads stop sound being transmitted from the speakers to the floor, microphones or other areas - so to ensure accurate sound, you need speaker pads

An alternative to gluing is hanging from hooks - simple to remove if necessary

Having foam covered walls will not dry the air - this one seems to be a myth