Average versus Total RMS power

HI,
I have version 2.0 of Audition and am trying to figure out how Audition is calculating the Average versus Total RMS power values shown in the amplitude statistics window. The Help section describes the two values as
Average RMS Power Shows the average amplitude. This value reflects perceived loudness.
Total RMS Power Represents the total power of the entire selection.
But I'm looking for the details regarding how they are coming up with these numbers.
Any thoughts?
Thanks,
Ben

BWYH wrote:
I'll generate a few test files and see if I can figure it out myself.
We've all been there and tried that, and the chances of coming up with an absolutely correct answer are not good at all - to the point of vanishing. The problem is that when the average value is computed, it's done something along the lines that Leq is calculated - but not quite. And even with absolutely fixed values in files, you will still find that variations in time make a significant difference to the results.
If you really want to know why you won't be able to do this just from a few files, it's because you will be trying to recreate the values in formulae like the ones here by working back from given results. I have an MSc. in acoustics, and I don't even fancy trying, quite frankly!

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How is TOTAL RMS different than AVERAGE RMS

I create spoken-word recordings. One company that I work with specifys that the recording should be at a level that measures between -23 RMS and -18RMS. It appears that audio editing programs label their RMS readings in various ways. I had been using Average RMS but I think maybe this company is using a standard that comes closer to what ADOBE calls TOTAL RMS. What attributes cause Audition to give one value to AVERAGE RMS and another value as AVERAGE RMS?

Total RMS used to be what happens if you add together all of the signals in your measuring time window (in Audition normally 50ms), and perform a RMS calculation on them, and that was a pretty standard way of measuring it. Average RMS in Audition is a little different, though. Reading through the somewhat cryptic help files about this reveals that to all intents and purposes, the RMS measurements will vary at different levels, because some attention is being paid to either Noise Criteria or Noise Rating curves. The lower the level gets with these, the more they favour lower frequencies over higher ones; in other words the figures reflect human annoyance factors rather than a specifically defined measurement criterion. And no, we can't tell you exactly how this is going to work, because the actual curves and weighting figures have never been made public, and it would take me several days to second-guess it from comparative readings. I simply don't have time...
It's been like this for ever. The original design of this was done by David Johnston, the program's original creator when it was Cool Edit, and I belive he's no longer associated even indirectly with Audition these days. Whether information about this is actually documented anywhere at all, I don't know. Questions about it come up periodically, and we can never answer them satisfactorily.
The original Cool Edit manual was just as useless about this. The exact words it uses to describe the Average RMS measurement are "Average RMS Power represents the average power of the entire selection. This is a good measure of the overall loudness of the waveform selection." And it's these words I've bolded that make the difference.
What happens with Total RMS measurements now seems to be a little different, and you end up with a figure much closer to a LUFS reading (you get this acccurately at the bottom of the statistics panel in CC). I know (because this is relatively recent) that the way the LUFS figure is calculated is according to the BS1770-2 standard - and that takes the whole program dynamics into account. What appears to happen with Total RMS in Audition is that it appears that an average of all of the windowed measurements, and that this in general turns out to be pretty close to the LUFS value as a rule.
Now, judging by the numbers they've quoted, the chances are that the company you are working for is using the recent standard for what you're doing - so if you are using CC, then it's pretty easy - select the whole waveform and quote them the value shown at the bottom of the screen. If you aren't using CC then there are several free LUFS meters available as VST plugins.
My personal view on this new standard, FWIW, is that it's a complete waste of time. It certainly doesn't achieve what it sets out to, or failing that all the broadcasters that use it have no idea what to do with it. And that very much includes the BBC, I'm afraid. The standard is supposed to keep overall programme dynamics within a certain loudness range, and save viewers/listeners having to adjust volume levels between programmes. And, it fails at that pretty comprehensively. Quite frankly, when it comes to broadcast dynamics standards, they'd have been better off forcing everybody to use the same settings on an Orban Optimod; that would almost certainly have worked better!

Average RMS power in Amplitude Statistics

I am wondering on how to calcuate the average RMS power using the window width? How does the window get the sample information from the sound file?
Thanks
Leo

>...but I could see that from a pure theory point of view it might be possible to "slide the window" over one sample at a time. That is how my professor (many years ago)in digital signal processing would have suggested it be done.
I don't think he would have! Let's take the standard sample window size of 50ms. At 44.1k that contains 2,205 samples. So there would be absolutely no point in sliding a dirty great window like that over a single sample at all, would there?
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Dallas, TX

Tony,
The PL/SQL forum may answer this better but had you considered the ROLLUP or CUBE GROUP BY functions? ROLLUP would look like this in your query:
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         perf_non_perf,
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Can i do this ?

I tried but it doesn;t work ...
PERFORM ALV_BUILD_FIELDCAT USING 'KONV' 'KWERT' 'ITAB' 'KWERT1'
' ' 'LME CASH CU' ' '    NA      NA    NA 'C' NA NA NA NA NA 'C601' NA.
      FORM alv_build_fieldcat                                       *
FORM ALV_BUILD_FIELDCAT USING REF_TABNAME
                          REF_FIELDNAME TABNAME FIELDNAME
                          KEY FTEXT HOTSPOT OUTLEN
                          ICON JUST DOSUM DECS NOZERO UOM
                          INP CHK EMF EDT.
ADD 1 TO COL_POS.
FIELDCAT_LN-REF_TABNAME   = REF_TABNAME.
FIELDCAT_LN-REF_FIELDNAME = REF_FIELDNAME.
FIELDCAT_LN-TABNAME       = TABNAME.
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FIELDCAT_LN-HOTSPOT       = HOTSPOT.
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FIELDCAT_LN-OUTPUTLEN     = OUTLEN.
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FIELDCAT_LN-CHECKBOX      = CHK.
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ENDIF.
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ENDFORM.                    "alv_build_fieldcat

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I am doing my research in order to find the best of the best 2.1 speaker system for my PC. I already have an AUDIGY 2 SE soundcard and I would like to support it with an excellent sound output set. While comparing different speaker systems I have came up with the following two best of the best products: Creative I-Trigue L3800 (Price 99GBP) and Logitech Z-2300 (Price 91GBP). Even if these are the best of the best it seems that they have a serious difference of power between them. Here is the RMS speaker power specifications:
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Subwoofer: 20 watts RMS Total peak power: 400 watts
My conclusion from the above data is that Logitech Speakers are 4 times more powerful from those of Creative (200 watts compared to 48 watts). Is my above conclusion correct? What else do I have to compare in order to buy the best system?

Clearly the " RMS " is the standard.
They do clarify their goofy ratings
in small print on some pages.
Those LT's you mention are great deal.
Very similar but in a revered brand - KLIPSCH -
a similar system is available for about $30. more.
That 'THX' certification is supposedly a big deal.
Big plus with the L3800 is remote controls functions
on Zen Vision M.
good luck

Creative uses less wattage to power the systems?

I directed my question to the support, but im not sure if they are going to reply on this.
I have Inspire P5800(72W total rms power) and the power adapter says 3,5 ACV, 5000mA which gives 67,5W (3A x 3,5V).So how they power 72W system with 67,5W adapter?
5W is not that much, you say, but how about this:
I was reading reviews on T600 and i just found that it has the same adapter as P5800 - 3,5 ACV, 5000mA which gives again 67,5W but the difference here is bigger since these speakers have 6W more rms power which gives more than 10% power loss due to the adapter.
So here are my questions:
How can creative supply different speaker setups with different wattage with the same power adapter?
Why they didnt mentioned anything about this?
Why they limit the systems by the power adapter? Trying to save money? Trying to cover bad speaker quality?
Also im wondering if there are other models affected by this issue too...

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How is actual bit depth measured

I am analyzing some recordings I made in 24-bit format in Audacity. Audacity can record true 24-bit integer files which Audition 3.0.1 recognizes as such.
After checking a couple of the files in Audition 3.0.1, I found that the meaning of "Actual bit depth" in the amplitude statistics is not entirely clear. It does seem to be based on the maximum peak in the file, but the bit estimate does not seem too clear.
For example, in one of the files if I select any portion that includes the highest peak and get amplitude statistics, the actual bit depth reported is 24. Example of a short selection that includes the peak:
Mono
Min Sample Value:    -22003
Max Sample Value:    26329
Peak Amplitude:    -1.9 dB
Possibly Clipped:    0
DC Offset:    -.003
Minimum RMS Power:    -44.45 dB
Maximum RMS Power:    -17.58 dB
Average RMS Power:    -30.18 dB
Total RMS Power:    -25.98 dB
Actual Bit Depth:    24 Bits
Using RMS Window of 50 ms
However, as far as I can tell, any selection in the same file that does not inlude the highest peak (but may include nearby close peaks) results in actual bit depth of 16:
Mono
Min Sample Value:    -20082
Max Sample Value:    22172
Peak Amplitude:    -3.39 dB
Possibly Clipped:    0
DC Offset:    -.001
Minimum RMS Power:    -54.14 dB
Maximum RMS Power:    -19.96 dB
Average RMS Power:    -36.26 dB
Total RMS Power:    -32.95 dB
Actual Bit Depth:    16 Bits
Using RMS Window of 50 ms
So it is unclear what level of peak amplitude distinguishes between 24- and 16-bit actual depth. If the bit-depth analysis is based on most-significant bits being zero, I would think that the trigger for identifying 16-bit actual depth in a 24-bit file would be to find that the 8 most-significant bits of the 24-bit samples are zero for all samples in the selection. So for a 24-bit integer file to have actual bit depth of 16 bits for a slection, the greatest peak would be less than -48 dBFS. But in the example above, the distinction seems to be having a peak amplitidue around -3.4 dB versus -1.9 dB.

>what actual difference does it make to anything?
Hard to say what difference it makes to anything without knowing what "actual bit depth" actually measures. It could be important, or could be useless. In the past I have not paid much attention to it because it is poorly described. It recently came to my attention because the files from a recent recording in 24-bit integer format were all reported as 16-bit "actual" bit depth. This is in contrast to some previous recordings made in the same way which were identified as 24-bit "actual". This implies there might be something different in the data formatting, the communication between the software and driver, between the driver and card, or something else.
It is a bit surprising that no one got Synt. to explain it properly.
>Oh, and the other thing about 24-bit int files is that they can lead you into a very false sense of security. If you decided, for instance, to reduce the amplitude of one by 48dB, then save it, and then decide to increase it again by that 48dB, you'd end up with a 24-bit file with just 16 bits of resolution - simply because it's an integer file. If you did the same thing with Audition's 32-bit floating point system, you'd lose no resolution at all.
In my workflow that produces original recordings in a 24-bit integer file format, the format is an efficient way of storing 24-bit integer data from a 24-bit card. Processing is another matter. I use the Audition preference to convert files automatically to 32-bit when opening.

Need work-around for 'amplitude statistics' bug

Does anyone know how to get adobe audition 3 to report the correct "amplitude statistics" for a selected audio clip?
It is obviously broken now (it worked fine in Cool edit Pro days), to show this simply do this:
create a new file
generate a one second sine wave at 1004 Hz,-6 dB amplitude, no modulation
check the "amplitude statistics" window
The results (for all or any part of the constant sine wave) should read -6 dB for all the catagories (Max, Min, Average, Total). In Audition 3 they typically read other (random?) numbers, however if you select a section of the sine wave near the middle with the selection length the same size as the amplitude statistics window it is sometimes possible to get the correct readings. Just the fact the reading change for various selections in a constant level sine wave shows there is a bug.
Fine.... but does anyone know if there is some way to get a correct reading out of Audition 3 ? Could I turn off some other features, or select the audio section to report the RMS level for in a very particular way?
Thank You.

Here is a really simple example of how adobe Audition 3 is reporting
incorrect values for the amplitude statistics of a selection that
only includes a CONSTANT AMPLITUDE SINE WAVE. Note that for a selection that has only includes a single constant RMS level signal, the reported RMS levels for:
MINIMUM RMS LEVEL
MAXIMUM RMS LEVEL
AVERAGE RMS LEVEL
TOTAL RMS LEVEL
should all be exactly the same (by defination ! ! !)
How to create an example of the incorrect reporting:
1) open Audition 3.0
2) create a new file (for example use mono 16 kHz, 16 bit depth)
3) generate 10 seconds of silence
4) make sure "Preferences-Data-smoothing" are both not checked
5) position cursor at 5 seconds (in middle of silence)
6) generate a sine wave at -6 dB amplitude, 1 second long
7) leave freshly generated sine wave selected
8) open amplitude statistics window
9) select "0 dB = FS sine wave" and default 50ms window width
10)note incorrect statistics reported:
Minimum RMS power -inf dB
Maximum RMS power -6 dB
Average RMS power -8.33 dB
Total RMS power -7.28 dB
At no point in the selection does a window have 50ms of -inf samples
The maximum power is correct
The average power is incorrect, it should also be -6 dB (constant sine wave!)
The total power should also read -6 dB, for a constant -6 dB sine wave
11) now close the amplitude statistics window and select the last 200ms of the
sine wave (from second 5.8 to 6.0)
12) open amplitude statistics windows again (still using 50 ms windows)
13) note the (really) incorrect statistics displayed:
Minimum RMS power -inf dB
Maximum RMS power -inf dB
Average RMS power -inf dB
Total RMS power -inf dB
I assert the Adobe Audition 3 amplitude statistics numbers are obviously wrong. It looks like the calculation is being done over
an incorrect section of some data buffer.

Average versus Total RMS power

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