[LAD] Calculate R M S

[Fons Adriaensen]

On Fri, Feb 18, 2011 at 11:30:24AM -0800, Mark Knecht wrote:
> On Wed, Feb 16, 2011 at 10:45 AM, Fons Adriaensen <fons at linuxaudio.org> wrote:
> <SNIP>
> >
> > Some filtering followed by RMS detection will provide a good
> > approximation to subjective loudness.
> >
> <SNIP>
> 
> Is this part to implement something like like Fletcher-Munson curves?

In general that is not the case, probably because for most types of
content the mid-frequency range is dominant. And loudness measuring
systems are expected to give good results for typical content, not
to estimate the subjective loudness of single tones or narrow band
signals.

The filter recommended by the ITU and EBU is a combination of a 2nd
order highpass (around 50 Hz) and a shelf filter providing 4 dB gain
at 4 kHz and above. Listening tests have shown this to work quite 
well in practice.

Ciao,

-- 
FA