in case ur wondering how i got here, i realised a couple of days ago that ppl wt hearing aids/cochlear implants hv the superpower to mute the sounds around them by taking their devices off so uh :P
(1) hearing aids vs cochlear implants
basically uh
so hearing aids are just hooked onto the ear and it basically makes the volume of everything louder. it has a microphone + amplifier + speaker and u can probably guess how they work based on those parts. but hearing aids dont directly tackle hearing loss - it literally just makes everything 🔊 LOOOOOOOOOOUDER 🔊 and this isnt effective for ppl with profound hearing loss. in comparison, cochlear implants do, sort of. they're also called "implants" for a reason, cuz they require surgery unlike hearing aids. oh and cochlear implants are DAMN EXPENSIVE, around like RM100K for device + surgery for EACH EAR. 💀😭
(2) revisiting how the ear works
^^ tadaaa this is ur ear hoorayyy. notice that spiral part in the inner ear called the cochlea? yeaaaa so that's where the cochlear implant goes, congrats for figuring that out. OH and even more interesting? cochlea = snail in greek bcs the cochlea looks like a snail shell lol 🐌
okok so how do we hear? ez oversimplified explanation: sound travels to ear -> eardrum vibrates -> ossicles vibrate -> fluid in cochlea vibrates -> hair cells in cochlea pick up vibrations and trigger electrical signals in auditory nerve -> signals sent to brain -> yay sound
also note that each hair cell in the cochlea doesn't pick up all frequencies, but instead only a certain range. and those hair cells are arranged so that different parts of the cochlea pick up different frequencies so like:
totally irrelevant info i found while researching:
try yawing rn - u shd feel/hear smth weird in ur ears. u can feel it when u swallow as well. mhmm yea so that's ur eustachian tube opening up, go search it up if u want. but ew i feel so conscious (and mildly disturbed?) abt that fact every time i swallow now HELPPP 😭😭😭
(3) cochlear implants
before FINALLY understanding how they work, first we gotta briefly understand the cause of (sensorineural) deafness in the first place. so in many cases, sensorineural hearing loss occurs when the hair cells in the cochlea are damaged, BUT the auditory nerve functions just fine. (in other cases, hearing loss may also result from damage to the nerve or CNS tho.) wokay here comes ur light-bulb moment: cochlear implants essentially play the role of the hair cells WOAHHH 😱😱🤯🤯
okay based on that diagram, u can probably already kinda guess how they work, and guess where that long electrode tail thingy goes? ...mhmm it coils up snuggly in the cochlea
so ez explanation: mic picks up sound -> processor converts to digital info -> transfers to receiver -> electrical signals sent through electrodes to auditory nerve -> signals sent to brain -> yay sound
so yes, literally, those electrodes do what the damaged hair cells are supposed to do. BUT, cochlear implants don't make everything sound normal. why? bcs most (modern) cochlear implants only have 22 electrodes per ear. in contrast, we have >3000 hair cells in each cochlea. (recall that each hair cell is specific to a certain frequency range.) so as u might guess, the frequency range with cochlear implants is limited compared to normal hearing. (and yes, the more electrodes the better. older implants had less electrodes.) this also makes it harder for ppl wt cochlear implants to pick up tones, so emotions and tonal languages (like mandarin) are more difficult to be understood. ppl hv described the sounds as "robotic" or "underwater" but it differs from person to person. i found some simulations here and here, but these are def not the most accurate. and also keep in mind that newer cochlear implants have more channels than the ones in the simulations.
welp the more you know yay 🌈 ✨ OKAY I SHD RLLY STOP PROCRASTINATING MY SCH WORK NOW BYE 💀