Sound Proofing -vs- Room Treatment

Dogbreath

Dogbreath

Im an ex-spurt
Sound Proofing

Achieved by MASS and decoupling.


Room Treatment

Achieved by strategical placement of frequency specific products.


discuss please.
:)
 
From what I've learned, and correct me if I'm wrong, but...
in general, with room treatment...

Smaller rooms require more bass trapping due to the close proximity of adjacent walls.
Since bass waves are stronger than any of the other frequencies, they tend to "crash" into each other and stomp the shit outta your higher freqs.

Small square rooms are especially bad mainly because of the "equalness" of the walls really makin a mess of the sound waves crashin and bouncing. No way you can get a clear picture of what you're doin.

In any room...bass trapping each corner to the left and right of your mixing station will always help the accuracy of your listening triangle.

sound about right so far?
 
With sound proofing...

can you get the mass by say...
2X4 framed wall, with one layer of 5/8 sheetrock...
followed by another 2X4 frame with another layer of (1/2 or 5/8) sheetrock?

Should you fill the gap between the walls with insulation or leave an air gap?

What about sand filled cinder blocks as you go up with the walls? That would be mass. No?

To decouple...

Seems to me like any thick rubber would do the trick.

Maybe a bunch of hockey pucks on the floor to separate it from the concrete floor you're building your nice wood floor over top of.

I saw this one dude who built a nice studio with slices of tires separating wall from floor, floor from ceiling etc.
kind of creative if not a bit redneckish. :D
but it worked just fine.

Just throwin ideas out here...;)
 
Imo you want a structure which has the ability to keep out all the sounds you do not want to record. Keeping out unwanted sounds/noise is the main reason for soundproofing. Room treatment on the other hand is whatever you can do to make the sound within the room sound the best it can. Ever wonder why the "pro studios" have different rooms for different instruments? Some rooms require slightly different treatment for certain instruments to sound their best. While the average home studio doesn't have multiple rooms (all with different treatments, designed to be instrument specific) a lot can be done with a single room. Good bass trapping, and a few diffusor panels can do a lot to make any room sound better. The main objective should be to stop as many of those nasty little reflections as possible so you can record the purest sound.
 
Dogbreath said:
...Since bass waves are stronger than any of the other frequencies, they tend to "crash" into each other and stomp the shit outta your higher freqs.

Small square rooms are especially bad mainly because of the "equalness" of the walls really makin a mess of the sound waves crashin and bouncing. ?
Click to expand...

http://www.hunecke.de/en/calculators/room-eigenmodes.html
Go here and see how your room sizes react. Equal and multiples of the same demension room sizes stack up.
 
Good find man. ;)

I started this thing off to help out those just gettin started but find I'm still learning too. :)
Cool.
 
Now, to *really* screw with your heads, there are two relevant ratings when we talk about sound proofing vs. acoustic treatment: NRC and STC respectively. Rooms with high NRC ratings are well isolated...not much sound coming in or out (from 125Hz to 4Khz anyhow). Rooms with high STC ratings are the most acoustically sound. So far, so good.

The problem is, those two goals work at cross purposes. In other words, the higher the NRC rating, the lower the STC rating will be and vice verse. The reason is intuitive if you think about it: a room that's well isolated will keep more low end trapped inside, making the treatment job harder. A room with a higher STC rating tends to release more low end to the outside.

The moral of the story is, you guys who plan to make build high NRC rooms...you better make sure you plan in plenty of acoustic treatment. You're gonna need it. :D

Frank
 
Dogbreath said:
What about sand filled cinder blocks as you go up with the walls? That would be mass. No?
Click to expand...

Hell yeah it would! I thought of that years ago, and I still think that'd be crazy good isolation. When I become independently wealthy, it will be done..

Dogbreath said:
Maybe a bunch of hockey pucks on the floor to separate it from the concrete floor you're building your nice wood floor over top of.
Click to expand...

Floating a floor, standard room-within-a-room design.. Just not practical in a house with 8' ceilings..
 
Ethan Winer said:
LOL, you mean those places that sell "soundproofing foam" are lying? :D

--Ethan
Click to expand...

Someone gave me a piece of that stuff, it's gotta be the best pad I ever found to sit my amp on. The floor hasn't complained about the noise since I've been using the foam so all the sales hype must be true. :)
 
Dogbreath said:
What about sand filled cinder blocks as you go up with the walls? That would be mass. No?
Click to expand...

Three-word warning here: USE DRY SAND. Seriously. Be very, very sure.

Dogbreath said:
To decouple...

Seems to me like any thick rubber would do the trick.
Click to expand...

Well, not exactly. It has to fall within a particular density range other wise it's just another thing to pass energy from one space to the adjacent space.

Frank
 
Weasel9992 said:
Three-word warning here: USE DRY SAND. Seriously. Be very, very sure.
Frank
Click to expand...

I do commercial / industrial architecture for my day job. It's not uncommon to grout the cells of a concrete block for structural purposes (usually with rebar inside). Grout or concrete might be a better choice to fill walls with.
 
Dogbreath said:
From what I've learned, and correct me if I'm wrong, but...
in general, with room treatment...

Smaller rooms require more bass trapping due to the close proximity of adjacent walls.
Since bass waves are stronger than any of the other frequencies, they tend to "crash" into each other and stomp the shit outta your higher freqs.

Small square rooms are especially bad mainly because of the "equalness" of the walls really makin a mess of the sound waves crashin and bouncing. No way you can get a clear picture of what you're doin.

In any room...bass trapping each corner to the left and right of your mixing station will always help the accuracy of your listening triangle.

sound about right so far?
Click to expand...

Small rooms are especially bad because the frequencies of the various modes are based on the dimensions of the room and smaller dimensions move a lot of isolated modes up into important audio frequency ranges. An 8 foot ceiling gives you a first axial mode at roughly 70 Hz, which is about the D string on a standard 4-string bass. :(

Modes start to get denser when you get to higher orders (and higher frequencies), but in a small room you might have to get well above 300 Hz before the modes start to get dense. The mayhem will typically be from 30 to 150 Hz. In a big venue, the modes may be dense by the time you get to 20Hz.

You can't generally control it unless you build your own space, but generally you want the lower modes to be uniformly spaced (at least 5% apart so they aren't degenerate, but not more than 20 Hz apart, so they don't act as isolated modes. Then, of course, you need to strategically install bass traps, starting with corners and then moving to other key spots (edges, etc.) until you can't stand to give up more space or run out of cash! :eek:

Square rooms are especially bad because the horizontal modes from the two directions will coincide and reinforce. :eek:

Dense, thick walls are great for isolation. :) They also strengthen the room modes. :(

Generally, you really can't do a lot about the existence of the modes. If you can get the relaxation times of all the modes short and relatively consistent, then you have done about the best you can do.

BTW, if you want a handy reference, the Master Handbook of Acoustics by F. Alton Everest is a great choice.

Cheers,

Otto
 
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