[philwelch]

> * hearing aids are commonly moulded to fit the individual, and thus have exceptionally good noise rejection.

> * They are designed to be worn for long periods of time without discomfort.

There are already headphones you can get that are moulded to the individual ear. Touring musicians use them on stage for monitors.

The problem with this is that extended hearing aid or in-ear headphone usage is not really the best thing for your ears. Your ears are supposed to ventilate. It's especially problematic if you have an ear infection.