[Joakal]

Hearing aids are designed to increase sound where the person can't hear as well. Sounds are faint? Hearing aid is a good choice. No therapy needed. Downsides is it that it amplifies noise too, requires batteries, maintenance.

Cochlear implant are designed with electrical signals directly to nerves but needs therapy to understand. Its akin to a legless person learning to walk again with new metal legs. Has similar issues as above with noise, etc, but the nerves are stimulated directly which allows more accurate hearing but not 100%. A major downside is that you lose 100% natural hearing in that ear as the nerve stimulation wires go inside the cochlear, effectively blocking any sound from going in. So imagine you lose a foot, and they offer you a metal leg to walk again and that requires therapy. Its a tough choice for some: some natural hearing or accurate but stimulated hearing.

Then the ear implant. Or really a natural cochlear implant is akin to attaching a new human leg to a legless person. Still, there's therapy needed. However, the cochlear is around the skull. So it's not as simple as taking it out and reattaching it. A lot of research is being done with promising results.

Later, the bionic cochlear, a complete electrical replacement of cochlear where you hear as well as a dog, but that's a dream.