Visualizing vowels as colored ACF images | Hacker News Reader

Visualizing vowels as colored ACF images

soundshader.github.io

26 pointsgbh444g10 comments

Hi HN! In my previous post, https://news.ycombinator.com/item?id=25037784, I presented so-called ACF images, where the auto-correlation function of a sound waveform is drawn in polar coordinates. It turned out that ACF images capture a good deal of sound symmetry.

This post is a natural extension of that idea. I've been thinking how to introduce colors into ACF images. ACF splits a waveform into a set of pure cosine waves and aligns them together by removing the phase. The idea is to color each cosine wave with the note it corresponds to, so when these waves are aligned, not only the amplitudes of the waves add up, but also their colors.

Are the overall amplitudes normalized? Some images appear brighter or darker than others, so I wonder if comparing them would be easier if there was some kind of perceptual brightness normalization step.

Amplitudes are normalized locally, using something like a moving average. Global normalization rarely works because most sounds have high dynamic loudness range.

It somehow reminds me of a sci-fi story (I believe by Ray Bradbury) about Martians being able to "see" sounds and music and the possibility - by injecting a drug - for humans to have the same possibility but only once in a lifetime and for a limited time, I cannot remember the exact title.

Correction, it was Asimov's, title is "The secret sense":

https://en.wikipedia.org/wiki/The_Secret_Sense

> Rougly (sic) speaking, the radial coordinate corresponds to time, the angular coordinate corresponds to frequency and color correponds (sic) to pitch or musical note.

Confused since pitch and frequency in my mind are the same thing. I googled around and there is precious little about this that I could find to enlighten me ... uses a pair of FFT's or some such.

It's probably note within octave, so 55, 110, 220, 440, 880, etc. would all get colored as "A".

Yep, that's the idea.

Neat, they're vaguely reminiscent of the heptapods' written language.

It immediately reminds me of Voyelles a poem, written in 1895 by Arthur Rimbaud

  A noir, E blanc, I rouge, U vert, O bleu : voyelles,
  Je dirai quelque jour vos naissances latentes :
  A, noir corset velu des mouches éclatantes
  Qui bombinent autour des puanteurs cruelles,
    
  Golfes d’ombre ; E, candeurs des vapeurs et des tentes,
  Lances des glaciers fiers, rois blancs, frissons d’ombelles ;
  I, pourpres, sang craché, rire des lèvres belles
  Dans la colère ou les ivresses pénitentes ;
  
  U, cycles, vibrements divins des mers virides,
  Paix des pâtis semés d’animaux, paix des rides
  Que l’alchimie imprime aux grands fronts studieux ;
  
  O, suprême Clairon plein des strideurs étranges,
  Silences traversés des Mondes et des Anges :
  — O l’Oméga, rayon violet de Ses Yeux !

Arthur Rimbaud, Poésies

But you’re right, it also looks like an alien alphabet. Very cool

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