Subject:RMS algorithm

Posted by: SonicCaveDan

Date:10/14/2005 11:21:26 AM

Is it possible to get the algorithm SF uses for deriving RMS values? Not sure how proprietary that is - it is a fairly standard algorithm though different applications use different varieties of the basic procedure. I need it to generate RMS values for large groups of files - it wouldn't work to have to load the files into SF one by one and scan them individually. Thanks for any info ...

dwf

Subject:RE: RMS algorithm

Reply by: mpd

Date:10/14/2005 2:02:57 PM

To calculate rms, you calculate the squart root of the average of the squares.

1. Square the data: y[n] = x[n]^2
2. Compute the average: mu = (sum(i=1..N) y) / N
3.. Compute the suqre root: rms = sqrt(mu)

Or roll it all together

rms = sqrt((sum(i=1..N) x[n]^2) / N)

Subject:RE: RMS algorithm

Reply by: SonicCaveDan

Date:10/18/2005 11:24:39 AM

I've gotten that far. What I don't seem to have is the calculation to convert that do "dB down from 0 dB". There is also the question of windowing. One algorithm I saw uses 50ms windows, gets the RMS value for each window, sorts them, then takes the value 5% from the highest one. There are definitely a few ways to skin this cat and I'm hoping to zero in on the one SF uses - code would be great ... thanks

dwf