Personal Sound Amplifiers (PSA)
Hearing aids are very expensive, typically from $3000 to $6000 a pair.
But some people might postpone wearing them, for many year.
I describe this alternative at my university website:
http://csam.montclair.edu/~kowalski/aps.htm
Feel free to share this short essay with others.
Comments will be appreciated.
Ludwik Kowalski (see Wikipedia)