A hearing aid is a straightforward device. Its microphone collects sound, its electronics amplify it, its tiny loudspeaker sends the sound into a tube placed in the ear canal, and the power comes from a disposable battery. There's just one problem: people hate hearing aids. They get lost. They're hard to wear while sleeping. They mustn't get wet. They get chewed up by the dog. They're awkward during sex.

I don't have a hearing aid. But I do have a cochlear implant. Cochlear implants are for people who are so deaf that even the most powerful hearing aids won't help. A processor worn on my ear collects sound and digitizes it, then transmits it by radio to a receiver embedded in my skull. The receiver sends pulses to electrodes attached to my auditory nerves.