How the cochlea computes (2024) • Hacker News Board

Re: How the cochlea computes (2024)

#71

Post by bonoboTP » Thu, Oct 30, 2025, 8:11 PM UTC

patrickthebold wrote: post #65

edbaskerville wrote: post #21

To summarize: the ear does not do a Fourier transform, but it does do a time-localized frequency-domain transform akin to wavelets (specifically, intermediate between wavelet and Gabor transforms). It does this because the sounds processed by the ear are often localized in time. The article also describes a theory that human speech evolved to occupy an unoccupied space in frequency vs. envelope duration space. It mak…

I think I might be missing something basic, but if you actually wanted to do a Fourier transform on the sound hitting your ear, wouldn't you need to wait your entire lifetime to compute it? It seems pretty clear that's not what is happening, since you can actually hear things as they happen.

Yes, for the vanilla Fourier transform you have to integrate from negative to positive infinity. But more practically you can put put a temporally finite-support window function on it, so you only analyze a part of it. Whenever you see a 2d spectrogram image in audio editing software, where the audio engineer can suppress a certain range of frequencies in a certain time period they use something like this.

It's called the short-time Fourier transform (STFT).

https://en.wikipedia.org/wiki/Short-time_Fourier_transform

Re: How the cochlea computes (2024)

#72

Post by xeonmc » Thu, Oct 30, 2025, 8:15 PM UTC

brcmthrowaway wrote: post #56

OT: Does anyone here believe in Intelligent Design?

As low-level physical mechanistic processes? Absolutely not.

As higher-order, statistically transparent abstract nudges of providence existing outside the confines of causality? Metaphysically interesting but philosophically futile.

Re: How the cochlea computes (2024)

#73

Post by antognini » Thu, Oct 30, 2025, 8:16 PM UTC

If you want to get really deep into this, Richard Lyon has spent decades developing the CARFAC model of human hearing: Cascade of Asymmetric Resonators with Fast-Acting Compression. As far as I know it's the most accurate digital model of human hearing.

He has a PDF of his book about human hearing on his website: https://dicklyon.com/hmh/Lyon_Hearing_book_01jan2018_smaller...

Re: How the cochlea computes (2024)

#74

Post by javier_e06 » Thu, Oct 30, 2025, 8:17 PM UTC

This is fascinating.

I know of vocoders in the military hardware that encode voices to resemble something more simple for compression (a low-tone male voice), smaller packets that take less bandwidth. This evolution of the ear to must also have evolved with our vocal chords and mouth to occupy available frequencies for transmission and reception for optimal communication.

The parallels with waveforms don't end there. Waveforms are also optimized for different terrains (urban, jungle).

Are languages organic waveforms optimized to ethnicity and terrain?

Cool article indeed.

Re: How the cochlea computes (2024)

#75

Post by IshKebab » Thu, Oct 30, 2025, 8:30 PM UTC

patrickthebold wrote: post #65

edbaskerville wrote: post #21

To summarize: the ear does not do a Fourier transform, but it does do a time-localized frequency-domain transform akin to wavelets (specifically, intermediate between wavelet and Gabor transforms). It does this because the sounds processed by the ear are often localized in time. The article also describes a theory that human speech evolved to occupy an unoccupied space in frequency vs. envelope duration space. It mak…

I think I might be missing something basic, but if you actually wanted to do a Fourier transform on the sound hitting your ear, wouldn't you need to wait your entire lifetime to compute it? It seems pretty clear that's not what is happening, since you can actually hear things as they happen.

Yes exactly. This is a classic "no cats and dogs don't actually rain from the sky" article.

Nobody who knows literally anything about signal processing thought the ear was doing a Fourier transform. Is it doing something like a STFT? Obviously yes and this article doesn't go against that.

Re: How the cochlea computes (2024)

#76

Post by IshKebab » Thu, Oct 30, 2025, 8:31 PM UTC

cherryteastain wrote: post #70

patrickthebold wrote: post #65

Earlier quoted context omitted.

I think I might be missing something basic, but if you actually wanted to do a Fourier transform on the sound hitting your ear, wouldn't you need to wait your entire lifetime to compute it? It seems pretty clear that's not what is happening, since you can actually hear things as they happen.

Not really, just as we can create spectrograms [1] for a real time audio feed without having to wait for the end of the recording by binning the signal into timewise chunks. [1] https://en.wikipedia.org/wiki/Spectrogram

Those use the Short-Time Fourier Transform, which is very much like what the ear does.

https://en.wikipedia.org/wiki/Short-time_Fourier_transform

Re: How the cochlea computes (2024)

#77

Post by jancsika » Thu, Oct 30, 2025, 8:34 PM UTC

hansvm wrote: post #64

lgas wrote: post #59

Earlier quoted context omitted.

> It does this because the sounds processed by the ear are often localized in time. What would it mean for a sound to not be localized in time?

It would look like a Fourier transform ;) Zooming in to cartoonish levels might drive the point home a bit. Suppose you have sound waves |---------|---------|---------| What is the frequency exactly 1/3 the way between the first two wave peaks? It's a nonsensical question. The frequency relates to the time delta between peaks, and looking locally at a sufficiently small region of time gives no information about that…

> It's a nonsensical question.

Are you talking about a discrete signal or a continuous signal?

Re: How the cochlea computes (2024)

#78

Post by Y_Y » Thu, Oct 30, 2025, 8:41 PM UTC

Terr_ wrote: post #57

a-dub wrote: post #30

Earlier quoted context omitted.

> At high frequencies, frequency resolution is sacrificed for temporal resolution, and vice versa at low frequencies. this is the time-frequency uncertainty principle. intuitively it can be understood by thinking about wavelength. the more stretched out the waveform is in time, the more of it you need to see in order to have a good representation of its frequency, but the more of it you see, the less precise you can…

> it also could just have a lot to do with the fact that, well, they have tiny articulators and tiny vocalizations! Now I'm imagining some alien shrew with vocal-cords (or syrinx, or whatever) that runs the entire length of its body, just so that it can emit lower-frequency noises for some reason.

Sounds like an antenna, if you'll accept electromagnetic noise then there are some fish that could pass for your shrew, e.g. https://en.wikipedia.org/wiki/Gymnotus

Re: How the cochlea computes (2024)

#79

Post by km3r » Thu, Oct 30, 2025, 8:45 PM UTC

edbaskerville wrote: post #21

To summarize: the ear does not do a Fourier transform, but it does do a time-localized frequency-domain transform akin to wavelets (specifically, intermediate between wavelet and Gabor transforms). It does this because the sounds processed by the ear are often localized in time. The article also describes a theory that human speech evolved to occupy an unoccupied space in frequency vs. envelope duration space. It mak…

> one would suspect that the specific characteristics of the human cochlea might be tuned to human speech while still being able to process environmental and animal sounds sufficiently well.

I wonder if these could be used to better master movies and television audio such that the dialogue is easier to hear.