Interpreting Room Acoustic Measurements

Posted: Sun May 18, 2008 3:33 am

MadMax wrote:

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.

Max,

I see the same thing you do - but draw a slightly different conclusion.

With an average of 75, 81 would be a 5dB peak and 71 would be a 4dB dip -

Although you would love to see this around 3dB (which means a 6dB spread) - in a small room, 4 to 5 dB is getting pretty durned good.

The 10dB you are hearing about would be dips and peaks in the 10dB range - for a total spread of 20 dB.

Rod

Posted: Sun May 18, 2008 9:08 am

Ahhhh!!! The lightbulb goes off!

Thanks for the clarification! So Bill's graph is not as significant of a change at I though it was.

Again, thanks for your patience Rod and Bill, forgive the partial hijack of your thread.

Posted: Sun May 18, 2008 11:28 am

MadMax wrote:

Quote:

Again, thanks for your patience Rod and Bill, forgive the partial hijack of your thread.

That's ok Max. You two probably needed to clear this up anyway before you get to the point of doing your own measurements.

Rod Gervais wrote:

Quote:

and when you're taking those (or any other measurements) you shouldn't be sitting in a chair and moving around.

My mistake. I was under the impression that the room should be measured with everything in it exactly as it would be when you are mixing. Thus, I was tryng to share the same space at the mix position with the mic stand holding the omni. I might have hit the base, or rolled back a couple of inches during the sweep.

I'll try again Monday, after I enclose the computer box.

Thanks to both of you for your input.

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