The Carina, a fully implantable hearing aid from Boulder-based Otologics, is in clinical trials. Credit: Peter Belanger

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.

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