On Wed, 24 Oct 2012 19:05:00 +0100, GB
wrote:

You've actually missed the whole point about how hearing aids work, and
why.

As we get older, the ears become less sensitive at high frequencies, but
retain their sensitivity at lower frequencies. Hence, hearing aids don't
just make everything louder. They boost the high frequencies, but not
the lower ones.

You'll need to build that into your hat, or it won't help.

Pah, trivially easy.
Russian fur hat with the flaps down or simple baseball cap with
extensions out to the lower sides, cunningly shaped as cartoon
characters to attract the local idiots.