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Comment by twelvechairs | Hacker News Reader

> no evidence that the human brain contains any hardware for pitch ratio detection. Consonance of simple ratios is a result of a simpler underlying rule,

My reading of your link is that it doesnt argue against pitch ratios being fundamental - what it does do is say that ratios are not only happening in chords but also in the sound of a single note, in different ways for different instruments.

This is very interesting work though and to me at least much more interesting than the headline post here which just points out the blindingly obvious (people raised in different musical cultures hear things differently)

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The most fundamental aspect of dissonance is the empirically measured Plomp and Levelt curve. This is approximated as: d(x)=e^(-3.5x)-e^(-5.75x), where x is the difference in frequency between two pure sine tones. (see http://sethares.engr.wisc.edu/paperspdf/consonance.pdf)

If we decompose sounds into sine waves, and sum the values on the Plomp and Levelt curve for all the pairs of sines, weighted by amplitude, then for the specific case of timbres based around the harmonic series, the minima for the dissonance curve happen to fall at simple ratios. This does not mean the brain is actually counting cycles! It's only a coincidence, and for other timbres the minima fall at different places.

The curve describes the (approximate) outcome. It doesnt prove or disprove how brain processes work. What we do know is that the outcomes are related to both these curves and simple ratios.

For me it seems logical that the brain (as a well established pattern matching machine) is probably doing something far more primative than calculating exponential curves. But if thats your view i cant disprove it.

The disconnect here is because the basic function of acoustic dissonance takes places in the hair cells of the ear. Harmonic ratios simply resonate hair cells in steady patterns rather than fast beat frequencies. (Slow beat frequencies are generally non-dissonant).

Studies like the OP's turn up every few years and are massively flawed due to oversimplification. Acoustic dissonance is waaaay more than a single-dimensional binary function... and then cultural layers are added.

Your comment makes me think of playing catch. Do we really calculate parabolas in our brain when choosing how to catch a ball?

What I've read is that the brain learns what the sight picture of a ball coming right to you should look like. When we run to catch a ball, what we're trying to do is line up with that sight picture.

Do you have some sources maybe? I find it very interesting, because it doesn't agree with my experiences.

I've never played baseball, but lots of basketball and soccer, and I get this "virtual trajectory of ball" overlay, so that I can adjust my body position, jump at the right time if needed.

Also often you look at ball, memorize where it will fall, then run to get there without looking at the ball. It can take seconds if it's a long ball in soccer, so it can't possibly be just adjusting to the sight picture.

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