The hearing aid is a challenging digital signal processing application. The amount of processing horsepower required is formidable, both to filter out ambient noise and to amplify and otherwise enhance sounds that are of importance, and especially considering that the signal processing chain must be traversed within a few milliseconds in order that the user doesn't perceive lip sync loss or other visual-to-audible delays. But long battery life is equally essential; no hearing aid owner wants to be constantly swapping out power cells.