Interpreting Room Acoustic Measurements

Posted: Fri May 16, 2008 8:37 am

MadMax wrote:

Quote:

If you have not already done one, I would suggest doing at least a waterfall and RT60. Post the results here, at John Sayers or Studio Tips

Ok, so here are the results using REW with an AT 3032 omni mic at ear level at the mix position.

http://www.westervillegolf.com/mxrimage.htm

The room is a standard small bedroom, 9' X 15' X 8', plaster walls and ceiling, hardwood floors, plugged windows, area rugs under the desk and at the back under a sofa.

Bass trapping in 3 corners, absorbtion cloud over the mix position. Broadband absorbers at the 1st relection points, and a curved dispertion panel on the back wall. Mix position is a 38% of long walls.

The instruction for REW explain the graphs, but give no information as to how to interpret them. What I would like to know is how these measurements compare to other's rooms that have been correctly treated, and how to interpret what actions should be taken for correction.

thanks.

Posted: Fri May 16, 2008 10:06 am

I know that many folks treat their bedroom control room with all sorts of crap. How to interpret the technical findings? To me, that stuff means absolutely nothing! That's why you have those two open holes on both sides of your head. If you don't know what you're listening to all the graphs and treatment mean absolutely nothing. They're just pretty pictures that tell you your control room doesn't sound.

You have no idea how many control rooms I've corrected after Acoustic Engineers have put up all sorts of stuff including 1/3rd octave active equalization . Then nobody understands why the control room still doesn't sound good? THE CONTROL ROOM IS TOO SMALL! That's why God created near field monitoring.

Godless engineer
Ms. Remy Ann David

Posted: Fri May 16, 2008 10:55 am

Bill, there's a good explanation of this stuff on my company's web site:

Using ETF

It doesn't explain all of the graphs you showed, but gives an overview of the process and explains waterfall graphs which is the key graph you need to understand. Feel free to follow up here with any questions.

--Ethan

Posted: Fri May 16, 2008 3:41 pm

Thanks Remy,

I agree wholeheartedly! It's just that in order to get answers on this forum, sometimes you have to be speaking the same language. My room sounds GREAT to me. I can hear every note in my favorite reference CD's clearly and can tell exactly where it is placed in the stereo field. Songs sound tight and crisp.

The problem is, now I can hear all the mistakes in my own songs. I need to re-record and mix them all. fortunately, it's only 6 songs.

Quote:

Godless engineer
Ms. Remy Ann David

I'm sorry. Is there anything I can do to help? I have a personal relationship with Him.

Ethan, thanks. I'll check out the link

Posted: Fri May 16, 2008 3:51 pm

Near field monitoring, is that what farmers use, by any chance?

Oh btw, did you hear about the farmer, who got an award for being outstanding in his field?

Laughing

Posted: Fri May 16, 2008 4:02 pm

Ethan,

Yeah, that's about what I figured. Add more traps - re-measure then repeat, 2nd ending then back to the coda.

Codemonkey,

Things slow in the moors today?

Posted: Fri May 16, 2008 7:54 pm

The analogy here is that all that Hi Definition helps us to observe, more of our human artifacts. This is precisely the reason why many on camera folks don't exactly appreciate Hi Definition video. It brings out all of their blemishes and imperfections on their skin. They don't like that. I don't either. Have you ever seen standard definition video projected onto a 30 x 50 foot screen? It looks damn fine. In high-definition, it looks ragged. So definition is good when definition is desired. Everything should not be always highly defined.

Your tennis shoes look better when one is green and one is purple
Ms. Remy Ann David

Posted: Fri May 16, 2008 8:11 pm

Moors? Naa. I live in teh city where we have teh new fangled internet. Moors are for people who can't afford hills.

Heh, Remy, 3000 posts. Don't reply though Razz

Posted: Fri May 16, 2008 8:17 pm

Bill,

To me, (like I'm Einstein on this stuff anyway) it looks like you're room is a good bit lopsided.

There's a definite rise in the low end that needs to be tamed a bit... so yeah... more trapping.

Superchunks in the corners can't hurt.

I'd snag a couple of bundles of 8 lb/sf mineral wool and stick em' in the corners and see what changes you get first... then if it's in the right direction... make the corner traps.

I'd suggest checking SPI out. Looks like there's a branch in Toledo...

Posted: Sat May 17, 2008 6:22 am

MadMax wrote:

Quote:

To me, (like I'm Einstein on this stuff anyway) it looks like you're room is a good bit lopsided.

There's a definite rise in the low end that needs to be tamed a bit...

So could someone please post a picture of what a good waterfall should look like? I'd like to see how many db variance from the target value the peaks and nulls are considered acceptable.

RemyRad wrote:

Quote:

So definition is good when definition is desired. Everything should not be always highly defined.

Having started listening more critically to music in the past year, I've realized that ther is a huge range of production and engineering values that are acceptable to music listeners. There is no 1 standard that can be used by all for comparison. Which only goes to prove that song and performance are the critical factors in the success of a recording.

So, therefore I would have to agree with this statement. Which poses the question: why did I start this thread in the first place?

Well, it's because I am a normally vain human being that likes to know how I compare to others I look up to. I haven't gotten to the point yet of being bi-shoe-hued.

Posted: Sat May 17, 2008 6:39 am

MadMax wrote:

To me, (like I'm Einstein on this stuff anyway) it looks like you're room is a good bit lopsided.

I don't see that - what I see is a bunch of background noise - - then the spike of the signal - which dissapears in roughly 490 ms. after which point you are left with the background noise.

The waterfall plot actually looks pretty good to me - not a lot of ringing - pretty even across the top - very small peaks and dips.

Bottom line is - if it sounds good - then it is good......... in the end - your ears are what it's all about - and the fact that your mixes have to be redone - because what had been before hidden is now revealed - that is more the proof that you got it done.

Rod

Posted: Sat May 17, 2008 7:00 am

Thanks Rod.

That's the kind of affirmation I was fishing for Thumbs Up

Actually, I thought the waterfall looked pretty good in comparison to the examples of untreated rooms I saw on Ethan's site.

The background noise probablyis the computer fan. I haven't had a chance to get the isolation box for it completed.

Posted: Sat May 17, 2008 8:01 am

I hate making statements that are inaccurate or are just plain wrong. Like I said, I've not gotten a lot of time reading those waterfalls, YET. (I have a feeling I will pretty shortly, though!)

What I was looking at, was the initial average line of 75db. When I draw a "straight" line through the waveform averages, it rises as you go lower in frequency... say, approximately 71-72db at 120Hz and approximately 81-82db at 20Hz. That's about a 10db rise (or fall) and it looks to be consistent all the way down.

I've seen it noted at places like Studio Tips and Sayers, that a delta of 10db is still pretty significant. Especially when it involves a rise as you go lower in frequency. e.g. the need for more trapping.

But then again, are the arguments for accuracy of 10db worth of change all that valid in that frequency range? (I'm asking so I can learn, as opposed to making a comment.)

Posted: Sat May 17, 2008 7:25 pm

MadMax, Rod,

Do you think that rise could be in part due to the computer fan noise, or maybe movement of my office chair on the hardwood floor?

Posted: Sun May 18, 2008 3:22 am

AwedOne wrote:

MadMax, Rod,

Do you think that rise could be in part due to the computer fan noise, or maybe movement of my office chair on the hardwood floor?

I have no idea what it could be - but I do know that before you even begin taking readings inside your room- you should ckeck for background levels - and when you're taking those (or any other measurements) you shouldn't be sitting in a chair and moving around.

Rod

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