Wow, this discussion about how our ears work is mind-blowing! It's amazing how complex sound processing is, and the comparison to signal processing concepts is really illuminating.
How the cochlea computes (2024)
141–150 of 159 posts
Re: How the cochlea computes (2024)
#142If 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...
Neither this article nor this book discuss the fact that hair cells phase lock to sound pulses. While individual neurons can fire no more than 200hz, populations of neurons are capable of phase locking to frequencies up to thousands of hertz.
Because cochlear implants only rely on stimulating the places in the cochlea related to particular frequencies but do not play the actual frequencies themselves (for reasons unknown), people with cochlear implants can detect frequency differences but lose appreciation for music.
Re: How the cochlea computes (2024)
#143Earlier quoted context omitted.
Yeah, it's sort of like saying the ear doesn't do "a" Fourier transform, it does a bunch of Fourier transforms on samples of data, with a varying tradeoff between temporal and frequency resolution. But most people would still say that's doing a Fourier transform. As the article briefly mentions, it's a tempting hypothesis that there is a relationship between the acoustic properties of human speech and the physical/ne…
> ...it's a tempting hypothesis that there is a relationship between the acoustic properties of human speech and the physical/neural structure of the auditory system. This seems trivially true in the sense that human speech is intelligible by humans; there are many sounds that humans cannot hear and/or distinguish, and speech does not involve those.
Yes, but at the least it's a bit more than that, because the ear is more sensitive to certain frequency ranges than others, and speech sounds seem to be more clustered in those ranges.
Re: How the cochlea computes (2024)
#144Somewhere here must lie the cure to tinnitus.
Re: How the cochlea computes (2024)
#145Somewhere here must lie the cure to tinnitus.
No, tinnitus beyond the cochlea, beyond the hearing nerve even, in some part of the audio processing brain tissue.
Cutting the hearing nerve does not cure tinnitus.
It develops due to a destruction of hearing cells that leads the brain to upregulate gain to catch a weak/absent signal, when the deprivation pattern is just right. (no tinnitus develops when the hearinf nerve is cut -> deprivation pattern matters)
Re: How the cochlea computes (2024)
#146Earlier quoted context omitted.
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 a…
The problem is that evolution works on a much longer timescale than the pace of change to the environment that humans cause.
While I understand the spirit of this comment, if you look at the fossil record you’ll see that’s objectively not true.
Roughly half of the shifts in the last 11 evolutionary periods, over the last 500 million years, were caused by changes that occurred in a-few-hours-to-a-few-thousand-years with 75%-90% species lost.
Evolution did not fail to work then.
Re: How the cochlea computes (2024)
#147The thesis about human speech occupying less crowded spectrum is well aligned with a book called "The Great Animal Orchestra" ( https://www.amazon.com/Great-Animal-Orchestra-Finding-Origin... ). That author details how the "dawn chorus" is composed of a vast number of species making noise, but who are able to pick out mating calls and other signals due to evolving their vocalizations into unique sonic niches. It's qu…
Birds have also evolved to choose when to vocalize to best be heard - doing so earlier in urban areas where later there will be more traffic noise, and later in some forest environments to avoid being drowned out by the early rising noisy insects.
My friend, through all these voluminous deafening comments, we certainly heard your loaded minimalist beautiful tune by you simply broadcasting your marvelous name!
Re: How the cochlea computes (2024)
#148Earlier quoted context omitted.
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 u…
Neuro person here.
Yes, many neurons fire at discrete intervals set by their morphology. In fact, this DFT/FFT/Infinite-FT/whatever-FT is all the hell over neuroscience. Many neurons don't really 'communicate' in just a single action potential. They are mostly firing at each other all the time, and the rate of firing is what communicates information. So neuron A is always popping at neuron B, but that tone/rate of popping is what affects change/information.
Now, this is not nearly true of every single neuron-neuron interaction. Some do use a single action potential (your patella knee reflex), some communicate with hundreds of other neurons (pyramidal cells in your cerebellum), some inhibit the firing of other neurons (gap/dendrite junction/axon interactions), some transmit information in opposite ways. It's a giant mess and the exact sub system is what you have to specify to get a handle on things.
Also, you get whole brain wave activity during different periods of sleep and awake cycles. So all the neurons will sync up their firing rates in certain areas when you're dreaming or taking an SAT of something. And yes, you can influence mass cyclic firing with powerful magnets (TCMS).
For the cochlea here, these hair cells are mostly firing all the time and then when a sound/frequency that they are 'tuned' to is heard, then their firing pattern changes and that information is then transmitted toward the parietal lobes. To be clear too, there are a lot of other brain structures in the way before the info gets to a place where you can be conscious of it. Things like the medial nuclei, the trapezoidal bodies, the caleyx of Held, etc. Most of these areas are for discriminating sounds and the location of sounds in space. So like when your fan is on for a long while and you no longer hear it, that's because of the other structures.
Re: How the cochlea computes (2024)
#149If 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...
Neither this article nor this book discuss the fact that hair cells phase lock to sound pulses. While individual neurons can fire no more than 200hz, populations of neurons are capable of phase locking to frequencies up to thousands of hertz. Because cochlear implants only rely on stimulating the places in the cochlea related to particular frequencies but do not play the actual frequencies themselves (for reasons unk…
Yes this is another important difference between human auditory perception and classical signal processing algorithms. Typically when processing audio we take a Fourier transform and then throw away the phase information. Mostly the amplitude information is all you need to understand a sound, but the ear actually is capable of picking up phase information.
(I thought this was discussed at some point in Lyon's book but it's admittedly been many years since I read it, so I can't remember for sure.)
Re: How the cochlea computes (2024)
#150> 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…
STFT?
Yesterday there was an article about how the ear works more like a Gabor transform or a wavelet transform than a Fourier transform, both of which are Short Time Fourier Transforms, so yes!