[PD] noise floor: median in audio signals, for peak extraction

Thomas Grill gr at grrrr.org
Sun Dec 25 21:09:39 CET 2011

Hi Alexandre,
maybe the libsms integration into Pd is of use for you - it calculates
a model of sinusoidals + residual noise, the latter representing a
kind of "noise floor".
Those components can then also be modified and resynthesized.

bests, gr~~~

2011/12/21 Alexandre Torres Porres <porres at gmail.com>:
> Hi there, this is a technique for calculating the noise floor of a spectrum,
> and extracting the peaks.
> It'd be used pretty much like I04.Noie Gate Miller's example, that has the
> "mask" table with a constant multiplier. We'd have instead this
> "noise-floor" block of audio, also multiplied by a constant.
> To get the noise floor, we take the magnitude (or power) spectrum and get
> the median of small bits of it, like every 32 samples. So the values of
> every 32 samples would be the median of that section...
> this is where I got this from, check page 4 and
> this would be kinda like using the [median] or [median_n] objects, but over
> audio blocks and not number lists.
> Since there's the need of calculating this in and using the result back in
> the same block round into the audio chain, I can't put the spectrum into a
> table, and then calculate the median over bits of it.
> But then, how to do it? Should I be able to pull this out only if I write a
> "median~" or [noise_floor~] external?
> Or somehow there's another way to do this with some existing external, or a
> similar technique, or even some audio math trick using [fexpr~] or
> something?
> This has to do with the other post I did about a project that attempts to
> isolate notes into a chord in a spectrum, something like melodyne is does.
> thanks
> Alex
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Thomas Grill

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