What are those gukky tubes for in old hearing aids...or

Handy can finally contribute something useful for a change. :wink:

Anyway, I was thinking about a guy I was in Kindergarten with years ago who wore a hearing aid that had those gukky tubes that seemed to always have some type of mucous garbage running through them. What were those for? He was only in class for the first year before the school that forced us to all write right-handed (I originally wrote with my left but can only do so now when I am not thinking about it) shipped him off to a school for the deaf.