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How the cochlea computes (2024)

dissonances.blog

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Re: How the cochlea computes (2024)

#111

Post by jibal »

kazinator wrote: post #22

> A Fourier transform has no explicit temporal precision, and resembles something closer to the waveforms on the right; this is not what the filters in the cochlea look like. Perhaps the ear does someting more vaguely analogous to a discrete Fourier transforms on samples of data, which is what we do in a lot of signal processing. In signal processing, we take windowed samples, and do discrete transforms on these. The…

The ear clearly doesn't operate on "samples of data", it doesn't "take windowed samples" ... there's an ongoing mechanical process.

Re: How the cochlea computes (2024)

#112

Post by anyfoo »

IshKebab wrote: post #110
anyfoo wrote: post #104

Earlier quoted context omitted.

Yes, but the article specifically says that it isn't like a short-time fourier transform either, but more like a wavelet transform, which is different yet again.

Barely different though. Obviously nobody is saying it's exactly a Fourier transform or a STFT. But it's very like a STFT (or a wavelet transform). The article is pretty much "cows aren't actually spheres guys".

I'd say the title is like that (and I agree with someone else's assessment of it being clickbait-y). I think the actual article does a pretty good job in distinguishing a lot of these transforms, and honing into which one matches most.

But the title instead makes it sound (pun unintended) that what the ear does is not about frequency decomposition at all.

Re: How the cochlea computes (2024)

#114

Post by actionfromafar »

anyfoo wrote: post #101
crazygringo wrote: post #88

Earlier quoted context omitted.

Yeah, this article feels like it's very much setting up a ridiculous strawman. Nobody who knows anything about signal processing has ever suggested that the ear performs a Fourier transform across infinite time . But the ear does perform something very much akin to the FFT (fast Fourier transform), turning discrete samples into intensities at frequencies -- which is, of course, what any reasonable person means when t…

Since we're being pedantic, there is some confusion of ideas here (even though you do make a valid overall point), and the strawman may not be as ridiculous. First, I think when you say FFT, you mean DFT. A Fourier transform is both non-discrete and infinite in time. A DTFT (discrete time fourier transform) is discrete, i.e. using samples, but infinite. A DFT (discrete fourier transform) is both finite (analyzed data…

Don’t neurons fire in bursts? That’s sort of discrete I guess.

Re: How the cochlea computes (2024)

#115

Post by fat_cantor »

superb-owl wrote: post #60

The title seems a little click-baity and basically wrong. Gabor transforms, wavelet transforms, etc are all generalizations of the fourier transform, which give you a spectrum analysis at each point in time The content is generally good but I'd argue that the ear is indeed doing very Fourier-y things.

It's a graduate student writing a journal club article about the Lewicki 2002 paper, which is very good, and whose abstract states the idea more precisely: "The form of the code depends on sound class, resembling a Fourier transformation when optimized for animal vocalizations and a wavelet transformation when optimized for non-biological environmental sounds"

Re: How the cochlea computes (2024)

#116

Post by smallnix »

actionfromafar wrote: post #114
anyfoo wrote: post #101

Earlier quoted context omitted.

Since we're being pedantic, there is some confusion of ideas here (even though you do make a valid overall point), and the strawman may not be as ridiculous. First, I think when you say FFT, you mean DFT. A Fourier transform is both non-discrete and infinite in time. A DTFT (discrete time fourier transform) is discrete, i.e. using samples, but infinite. A DFT (discrete fourier transform) is both finite (analyzed data…

Don’t neurons fire in bursts? That’s sort of discrete I guess.

I was also thinking of refractory periods with neurotransmitters. But I don't know much about this.

Re: How the cochlea computes (2024)

#117

Post by anyfoo »

actionfromafar wrote: post #114
anyfoo wrote: post #101

Earlier quoted context omitted.

Since we're being pedantic, there is some confusion of ideas here (even though you do make a valid overall point), and the strawman may not be as ridiculous. First, I think when you say FFT, you mean DFT. A Fourier transform is both non-discrete and infinite in time. A DTFT (discrete time fourier transform) is discrete, i.e. using samples, but infinite. A DFT (discrete fourier transform) is both finite (analyzed data…

Don’t neurons fire in bursts? That’s sort of discrete I guess.

Even if they do (and I honestly have no idea), isn't it the frequency, i.e. the output of the basilar membrane in the ear, and not a sample in time of the actual sound wave which would correspond to a short-time frequency transform, that gets sampled here?

And the basilar membrane seems like a pretty un-discrete (in time, not in frequency) process to me. But I'm not 100% sure.

Sure, if you go small enough, you end up with discrete structures sooner or later (molecules, atoms, quantum if you go far down enough and everything breaks apart anyway), but without knowing anything, the sensitivity of this whole process still seems better modeled as continuous rather than discrete, the scale at which that happens seems just too small to me.

Re: How the cochlea computes (2024)

#118

Post by anyfoo »

smallnix wrote: post #116
actionfromafar wrote: post #114

Earlier quoted context omitted.

Don’t neurons fire in bursts? That’s sort of discrete I guess.

I was also thinking of refractory periods with neurotransmitters. But I don't know much about this.

It's a good question, but as elaborated in a sibling comment, I'm not sure it even matters in this case. (Sampling frequency vs. sampling the sound wave itself.)

Re: How the cochlea computes (2024)

#119

Post by tsoukase »

As the auditory associative cortex in parietal lobe discriminates frequencies, there must be some time-frequency transform between the ear and the brain. This must be discrete (as neurons fire in bursts and there is a finite frequency resolution capacity) and finite time.

The poor man's conversion of finite to equivalent infinite time is if you assume an infinite signal where the initial finite one is repeated infinately to the past and the future.

Re: How the cochlea computes (2024)

#120

Post by kulahan »

jibal wrote: post #109
kulahan wrote: post #62

Earlier quoted context omitted.

Probably worth mentioning that as evolutions that allow them to compete well in nature die out, ones that allow them to compete well in cities takes their place. Evolution is always a series of tradeoffs. Maybe we don't have sonic variation, but temporal instead.

The dying out of birds "in nature" and the adaptations to cities are largely independent as they occur in different populations.

It's about filling open niches. City birds were an open niche for a long time. The ones who adapted to handle that better are thriving in better population numbers than those which can only survive with 13 specific types of trees.

Even still, among the populations of birds not adapting to the city, they are being forcibly adapted in other ways. If the reach is too big, they die.

This is how evolution works, and has always worked. The world shifts, and those who can handle it thrive, while those who can't, suffer. It's the reason mammals are running the planet today when it was lizards just a couple million years ago.

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