Hearing is kind of fascinating if you calculate the power supplied to the eardrum in the ~0 dB range, we're talking about attowatts of sound power generating movements in the single-digit nanometer range, which is still picked up and converted to a neuronal response. Meanwhile the whole thing suppresses the far greater pressure fluctuations due to your heartbeat and other movements quite well, and can reasonably cope with a ~120 dB dynamic range (though this is damaging fairly quickly).
Pro DJ here... Agree with the rest of your comment except for... "Where vision shines is distinguishing where the signal comes from."
Suggest closing your eyes and having someone else snap their fingers around you, you'll know immediately where that sound came from. This is accomplished by your mind differentiating the slight time difference between when your left and right ear register the noise as well as the volume difference.
This innate ability can be developed by DJ's to take two songs playing at different speeds and speed or slow them down to match. This is called "beat matching" and before software made this more accessible (aka more automated) it was the key skill necessary for DJ'ing as it allows seamless transitions between songs.
I still find your comment insightful and interesting, I just had to nitpick that one part.
They are orthogonal. Hearing has phase and continuous wideband frequency information but only two channels. Eyesight has millions of channels but discretized narrowband frequency and no phase information.
A many-channel sense with full frequency, phase, polarization, ... information would presumably be very hard to process usefully.
If so, then it's even more stunning that the communication channel to the auditory cortex is quiet enough to carry a massive disturbance + a tiny signal, and still preserve that signal after subtracting out the disturbance.
That would be very difficult to accomplish electronically.
The brain doesn't compute it, the cochlear is an fft! It is a cone shaped structure (that is curled up) that is covered in hairs and neurons. The fatter end is used for low freq and the thinner end is used for hi freq. So the brain takes audio in the frequency domain, not as continuous samples!
(I did an Anatomy degree almost 20years ago now, all from memory)
The person you are responding to is right and your assertion is incorrect. The person you replied to knows the ear delivers a frequency domain representation. They were disagreeing with the FFT part.
The FFT is a specific mathematical construction that carries out a Fourier Transform efficiently through a hierarchy of "butterfly" steps. The ear has no such thing. It is just ~20,000 hair cells, each resonant to a specific frequency. That is, each computation is local, very unlike the FFT.
I can roughly recall the mechanism by which it worked, and was told that this was an analog for how the Fourier transformation worked, and I vaguely remember going through one on paper. The spiral of the cochlear seems an analog of how the harmonium works. Does the earlier poster have a point with regard to the cochlear as a physical object performing a Fourier transform (though perhaps not a fast one)?
Fourier transform is different from FFT, which is Fast Fourier Transform. FFT is an optimization that involves decomposing a signal into multiple "smaller" signals, recursively performing FFT on those, and then combining the results.
The accurate way of saying this is that the cochlear does Fourier analysis.
Folks around here don't handle ambiguity well, and are treating your comment like it's wrong, rather than basically correct except for a harmless conflation of an algorithm for something with the thing itself.
No, that's also not accurate. Words mean things. We know that parts of the cochlea respond to different frequencies, but that does remotely imply that the auditory system is doing Fourier analysis, which is a high level mathematical transform with a specific set of formulations. "Fourier Analysis" does not describe every possible method of extracting frequency content from a signal.
> Fourier analysis of discharge patterns in response to sinusoidal acoustic stimulation provides a consistent and repeatable measure of response phase and amplitude. The Journal of the Acoustical Society of America 58, 867 (1975); https://doi.org/10.1121/1.380735
> sinusoidal frequency domain decomposition of sound waves is a key mechanical phenomenon exploited by our hearing system, leading to in effect a frequency domain transformation of the temporal pattern of compressions and rarefactions that we term sound.https://uncommondescent.com/video/hearing-the-cochlea-the-fr...
That one has a video.
Your case is roughly as incoherent as one which claims that a thrown ball does not perform Newtonian physics. It doesn't have to.
Now that we've disposed of the nonsense that cochlear response is not meaningfully modeled with Fourier analysis, interested parties might have fun with research into all the ways this model is not perfect. I've got a paper loaded in my reader claiming it's actually wavelet analysis, for when I have time and inclination to read it.
WHAT?! :> I'm at ACL and can't hear a fucking thing. ;)
I wonder about the limits of the muscles of the eardrum (TT and stapedius) to prevent hearing damage. For example, I recall awaking one morning being unable to hear because those muscles were isometrically flexing to a degree that prevented the eardrum from move normally. I thought I lost my hearing but then they started to relax over a few minutes.
I don't know if anyone else can, but I can consciously make both eardrums vibrate creating a sound like a rumble.
Last thing: I can hear my left eye move. I have a SCDS that I was able to identify myself as it's the only condition with this rare symptom. There is a tiny hole in the thin, porous bone between my inner ear and brain. It can be fixed surgically but requires brain surgery that effectively jacks the brain up and out of the way to be repaired by a surgical otolaryngologist. Eating chips is horrendously loud. Exercising leads to hearing my pulse. The risks of surgery though make me think it's worth enduring annoyances, although I don't know if it's causing extra cognitive load (distraction filtering) or balance problems. Oh and tinnitus from hell.. REEEEEE.
What you hear vibrating is not your ear drums themselves, but is a muscle called the tensor tympani. It aids in dampening loud sounds like chewing or screaming. I can also do this.
Yep, the TT. Thanks for precise elucidation. It's layman's terminology because I'm uncertain of the audience composition as HN has become less Ivy League than it once was.
> For example, I recall awaking one morning being unable to hear because those muscles were isometrically flexing to a degree that prevented the eardrum from move normally. I thought I lost my hearing but then they started to relax over a few minutes.
I remember listening to a podcast where one of the guests experienced a highly stressful event. They mentioned that they felt like they couldn't hear anything for a few weeks but the problem eventually went away.
When I heard this, I assumed it was some kind of psychosomatic effect but reading this made me realize that it could also be related to actual physiological responses to stress. (You could argue that psychosomatic responses are also physiological so I'm drawing a distinction between "your brain stopped you from hearing" vs "your body was so stressed out, your ears stopped you from hearing".)
A good deal of this appears, in my opinion, to be the press release overselling what has been done in research with their employees involved now being published in Nature.
The function on physical and physiological levels has largely been well understood and that knowledge still stands in the light of this publication.
What the researchers are reporting appears to be a more detailed structural description of this sensory protein complex, and the additional structure information combined with simulations of known physics and chemistry in turn suggests additional detail about of how the "signal" occurs on the molecular level.
Disclaimer that I didn't take time to read the whole thing now, but that's the gist of it from summaries and skimming.
It is, with little doubt, some valuable pieces of information in the context Collective Knowledge of Mankind, and keeping large, complex, multipart molecular machines like this reasonably stable and normal for examination is arduous work, so I don't mean to denigrate the studies or the scientific paper, but as so often the way this is being spun in the press release is regrettable.
According to the article and the paper we now have a clear understanding of how it works - the proteins in worms (which are similar to humans in their hearing structures) and their function.
So, unless I misread it, we absolutely know how sound > neural impulse works.
More:
> The initial step in the sensory transduction pathway underpinning hearing and balance in mammals involves the conversion of force into the gating of a mechanosensory transduction channel1. Despite the profound socioeconomic impacts of hearing disorders and the fundamental biological significance of understanding mechanosensory transduction, the composition, structure and mechanism of the mechanosensory transduction complex have remained poorly characterized. Here we report the single-particle cryo-electron microscopy structure of the native transmembrane channel-like protein 1 (TMC-1) mechanosensory transduction complex isolated from Caenorhabditis elegans. The two-fold symmetric complex is composed of two copies each of the pore-forming TMC-1 subunit, the calcium-binding protein CALM-1 and the transmembrane inner ear protein TMIE. CALM-1 makes extensive contacts with the cytoplasmic face of the TMC-1 subunits, whereas the single-pass TMIE subunits reside on the periphery of the complex, poised like the handles of an accordion. A subset of complexes additionally includes a single arrestin-like protein, arrestin domain protein (ARRD-6), bound to a CALM-1 subunit. Single-particle reconstructions and molecular dynamics simulations show how the mechanosensory transduction complex deforms the membrane bilayer and suggest crucial roles for lipid–protein interactions in the mechanism by which mechanical force is transduced to ion channel gating.
Smell (chemical environment) was probably the "original" sense, followed quickly by touch (slow macro pressure) and hearing (fast micro pressure). Pretty much every animal has those, even if they lack the brains to do much sophisticated with them.
Sight came way, way, way, way, way, way, way later. Encoding language in sounds is an even more recent innovation, in the grand scheme.
This may also be why we have such trouble assigning words to smells, and you can't write a poem to replace a hug, for instance. They're processed by entirely different, and far more primal, parts of the brain than language.
I never thought about it before but if someone had asked me I probably would have guessed the same - humans are probably biased to assume hearing must involve ears.
OTOH, detection of mechanical vibrations seems like the kind of adaptation to evolve early. Hearing is in some sense just a refinement of that, so at the very least the groundwork for it must be old.
Remarkable nature. Whenever my daily problems get on top of me, I like to spend a moment to think about the absurd but beautiful reality that we creatures exist and that we're hurtling through space. And now... that worms can hear... in a way similar enough to humans.
>So, unless I misread it, we absolutely know how sound > neural impulse works
Am I being unclear?
I asked : did we always consider it to be a mystery? Or did we have a different model before? (Which just recently got replaced by this new, better, model)
As it is said in the article, “Scientists exploited the fact that the roundworm Caenorhabditis elegans harbors a mechanosensory complex very similar to that of humans.” So, not only in worms.
This isn't about a drug. Those have some very specific conditions under which they have to do their thing. This is about a mechanism for transducing oscillatory forces to a neuronal signal, and it describes the exact structure. There are still holes in the pathway, but it looks very interesting to me, and (from my lay understanding) generic enough. You wouldn't say that a study into a rat's retina is completely irrelevant to human eye sight, would you?
> You wouldn't say that a study into a rat's retina is completely irrelevant to human eye sight, would you?
Er, probably? Not completely irrelevant, and perfectly valuable in laying out the groundwork for how we suspect things might work, but I also wouldn't trust it until somebody had it separately verified that human retinas actually worked the same way.
> and (from my lay understanding) generic enough
Yes, if that's true then it's interesting. I'm just extremely cautious of assuming that the things in question are in fact the same. I think the drug analogy does in fact hold, because if the mechanisms were the same them I would expect artificially chemically altering them to play out the same. And also in fairness, that frequently does work! But it also doesn't work in many cases, hence my being extremely cautious until somebody actually does the leg work to verify that humans are actually the same.
