[LAU] Normalizing Audio Levels using RMS

[Justin Smith]

On Tue, Apr 14, 2009 at 8:28 AM, Dave Phillips <dlphillips at woh.rr.com> wrote:
> Viktor Mastoridis a écrit :
>>>> Hi Linux Audio Geeks
>>>>
>>>> In my musical prehistory, while I was on Windows, I used to use a
>>>> program called SoundForge that had one very useful feature: normalizing
>>>> audio levels with RMS, even using the Equal Loudness Contour
>>>>
>>>> For a whole year I am struggling now to find something similar on Linux,
>>>> without much success.
>>>>
>>>> Any help/hints will be much appreciated.
>>>>
>>>> Viktor
>>>>
>
> The ReZound soundfile editor includes an Adaptive Normalize that "uses
> an RMS level detector (defined by the window time) and adjusts the
> amplitude inversely proportional to the signal level. As the level drops
> the gain increases; as the level rises the gain decreases. There is also
> a max gain limit so that silence does not get amplified by infinity
> (when the maximum gain level is not being imposed). The formula is:
>
> output = input*normalization level / current signal level
>
> If Lock Channels is enabled the signal level will be calculated across
> all selected channels which will preserve stereo phase."
>
> But I'm not sure it's what you're looking for.
>
> Best,
>
> dp
>
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If you want to normalize amplitude, the rezound algorithm works just
fine, if you want to normalize loudness, then you want to use jamin,
or some other program that processes different frequency ranges
separately, since the human ear does not have a flat frequency
response, loudness is frequency dependent. In regards to measuring in
terms of RMS or not, someone else will have to address that.