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how do dynamic range meters work?

post #1 of 5
1/16/12 at 3:16pm
Thread Starter 

I've been reading up on the loudness war reciently and decided to download a dynamic range meter for foobar2000. after checking some of my music i noticed that on some tracks there were huge discrepancies between what i percieved the dynamic range to be and what it was measured to be. this was surprising, so i imported two tracks into audacity to visually compare them.

DynamicRange.png

(wont link to the tracks as they probably arent appropriate for a family friendly site)

the top track (DR4) is something that i had considered to be one of the more dynamic and relaxed dubstep tracks i've ever heard, while the bottom track (DR6) was described on release by the artist as "really stupid, really loud".

looking at and listening to the tracks gives me a completely different impression to what the DR meter gave, so i was wondering how these meters measure DR, as i really can't reconcile the measurements with everything else.

thanks in advance.

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post #2 of 5
1/19/12 at 1:08pm

I don't know all the details of how it's calculated, but the numbers you see are not as simple as "highest signal compared to lowest signal in the recording." Since there is some silence in almost all recordings, this would mean they all have DR approaching 90dB, which we know is not the case.

 

I looked at the website for that plugin and found this document: http://www.dynamicrange.de/sites/default/files/tech3341.pdf

 

It has some information about a spec for calculating the DR, I assume this is what's used in the tool. Of particular interest (to me) was the fact that different timescales are considered for the calculation ("momentary," "short-term," and "integrated.")

 

My guess is that even though the waveforms look a certain way, the calculation is doing something you as a human wouldn't. Perhaps the first track approximates 2 sections of "approximately brickwalled" waveforms, separated by "almost silence," when considering the measurement thresholds and intervals they used. Whereas the second recording may have had a little more variance over the large timescales, even though it is a higher level overall. I just don't know. But there is something to be said here for not trusting a number blindly. Maybe someone who understands the measurements a little more can tell us why they come out this way.

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post #3 of 5
1/19/12 at 1:29pm

Just guessing here, but I believe dynamic range would be calculated as quietest vs. loudest over small intervals. The first track may appear more dynamic because it has loud parts and quiet parts, but look at the difference between the dark and light blue (which basically signifies loud and quiet over very small intervals). The difference between dark and light blue at any given point is smaller than the difference in the second waveform. Notice the RMS value in DR Meter. That's closer to what you're thinking, which is average volume. The second track has less dynamic compression, but is still louder. The two are exclusive, just often found together.

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post #4 of 5
1/20/12 at 12:53pm
Quote:
Originally Posted by Head Injury View Post

Just guessing here, but I believe dynamic range would be calculated as quietest vs. loudest over small intervals. The first track may appear more dynamic because it has loud parts and quiet parts, but look at the difference between the dark and light blue (which basically signifies loud and quiet over very small intervals). The difference between dark and light blue at any given point is smaller than the difference in the second waveform. Notice the RMS value in DR Meter. That's closer to what you're thinking, which is average volume. The second track has less dynamic compression, but is still louder. The two are exclusive, just often found together.


A "small" interval isn't well-defined, but I get your point. That was what I was trying to convey in my first post - the calculation of dynamic range depends on what intervals you look at.

 

So it's not equivalent to "eyeing the track," which is what caused the confusion in the first place. Eyeing the track may not be the best indicator of dynamic range wink.gif

 

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post #5 of 5
1/20/12 at 1:51pm
Thread Starter 

Thanks for the replies. my initial asumption on how it would be calculated would be sampling the level across the entire track, then taking a mean and an SD/VAR, which would reported as the dynamic range, or something similar. from what i understand you're saying that it calculates based on average rate of change across small intervals (correct me if i'm misinterpreting). i can see how that would explain the differences between what was measured and what i heard.

i'm still a little confused about how to interpret the measurements, so if anyone could point me to documents explaining how to interpret these mesurements or how the calculations are made that would be great.

thanks again.

EDIT:

Had a second read through that link Iniamyen posted. the maths is a little over my head but it seams to agree with the idea of small intervals being used rather than a measure of variation across the whole song. i'm still not  entirely sure on how to interpret measurements, but i think i've got a better idea now.


Edited by Salm0n - 1/21/12 at 1:26pm
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