[PD] isosonic curves : level the perceptual loudness of different pitches

IOhannes m zmoelnig zmoelnig at iem.at
Thu Jan 25 18:52:57 CET 2007

Alexandre Quessy wrote:
> Hi all,
> I would like to create an abstraction to adjust the amplitude of
> synthetic sounds according to the ear sensitivity. At a given
> amplitude, we hear the notes in the middle range louder than the high
> and low notes. This perceptual property of the audition can be
> somewhat undesired in a musical work. (in my opinion at least)
> The equal lines of actual amplitude of notes that seem to have the
> same loudness are called "isosonic curves". Here are 2 different
> graphics of these curves :
> http://www.multimedia.uqam.ca/cours/audio/images/diag/sonpsy_isoson.gif
> http://www.comm.uqam.ca/GRAM/illu/mus/nature/CourbeDIsosonie.GIF
> A few links that might give you a few hint for the calculations :
> http://en.wikipedia.org/wiki/DB%28A%29
> http://en.wikipedia.org/wiki/Weighting_filter
> http://en.wikipedia.org/wiki/Stevens%27_power_law
> Anyone would have a formula or a table containing data that could help
> me to calculate this ? For instance, we would be able to generate sine
> waves of any frequencies that would be perceived as having the same
> intensity for all of them, by changing their amplitude according to
> this leveling formula . This way, we could hear our low freq notes as
> much as the middle ones. Very valuable. :)

btw, there is an object in iemmatrix called [mtx_phon_curve] which
should give you what you want.

since it is an abstraction, you can even see how the curves are created.


> Thanks !

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