Ears are not very robust. They are damaged easily and don't heal afterwards. This is most likely because:
1. Anything in our ancestral habitat that would be cataclysmic enough to damage our hearing (lightning strikes, boulders falling, volcanos) would also be likely to kill us.
2. Losing our
hearing doesn't have a huge effect on whether we live long enough to procreate. It makes us less fit, but not to the point where we would get eaten immediately.
Of course now we have machines and loud music to destroy our hearing forever. I know mine has been somewhat damaged by lawnmowing jobs and too many forgotten earplugs at metal concerts. \m/
The proposed device would be an all-purpose hearing enhancement, similar in form to a hearing aid, but with several features:
1. Hearing protection - The device would use an audio level compression or limiting scheme to attenuate really loud sounds. If the device were turned off it would just behave like a regular earplug, so it can certainly attenuate well.
2. Amplification - It could also be configured to increase the level of quiet signals, to give a "bionic ears" effect. Most people would probably leave this feature off except for special situations. Maybe it could be triggered to turn on when the user moves their ears, like an animal would perk up their ears to hear better. (Not that everyone can do this, of course.)
3. Arbitrary signal input - Also it would allow any type of audio signal to be sent wirelessly directly into the ear, obsoleting headphones, cell phone speakers, car stereos, etc. Obviously this would need some kind of security features and such so people aren't beaming ads directly into your ears.
Potential problems:
1. Fidelity - No one will want them if they alter sound quality or have limited bandwidth. They will need to be a hi-fi stereo system in a tiny little package. Probably the state of the art expensive hearing aids are not that bad, though. I don't know; I've never worn one. They've certainly been around long enough to perfect this art.
2. Directional cues - The input to output phase shift and such needs to behave the same as the ear canal would have, so that we can still pick up on directional cues from the way things reflect off the outer ear folds, etc.
3. Delay/response time - Related to the above. If the signal takes longer to get from ear opening to eardrum than normal, it will certainly be confusing for the user. Not sure how well humans can adapt to changes like this delay, but it would necessarily hamper our response time a bit even if we adapted to it.
Luckily, we are helped by the fact that electromagnetic waves move a little bit faster than sound waves. (Roughly 800,000 times faster, in fact, according to google calculator.) So we can definitely get our signal from input to output faster than the sound would have traveled the same distance. The bottleneck is then processing time. For an implant that takes up 1 cm of ear canal length, we have 30 millionths of a second to process our signal and get it back into sound. This would either require very fast digital hardware or complicated analog hardware, both of which would be hard to fit into such a small place. But this is not completely outlandish. A DSP dedicated to a few simple functions can be made much smaller and faster than a general microprocessor.
"The outer ear consists of an ear flap and an approximately 2-cm long ear canal." Hmm...
The hearing protection algorithm requires significant delay, though. All real audio compressors delay in the milliseconds, I believe. Is it possible to build a slope-based, predictive version? Remember a few milliseconds into the past and if the waves are getting louder and louder and the current wave has a very high slope you should start cutting back on it. Or something.
3. Control - To switch on and off different functions, set basic level, etc. Most likely a wireless remote control.
Same potential problems as a regular ear canal hearing aid:
4. Power source
5. Ear canal shape and size changes over time
6. Does earwax need to get out? Would it be harmful to leave these in constantly?