Hearing Stuff
The earliest hearing aids were ear trumpets invented sometime in the 17th century. They were long horns with one large opening at one end and a smaller opening at the other end, which was placed in the ear. The principle behind this instrument being that sound pressure waves entering the large end are
condensed into smaller volume, thereby increasing the audible sound pressure.
The first electronic aid was a telephone invented by Alexander Graham Bell in 1876 that converted sound pressure waves to a current and then back to waves.
Who's Deaf?
An old man was wondering if his wife had a hearing problem.
So one night, he stood behind her while she was sitting in her lounge chair.
He spoke softly to her, "Honey, can you hear me?"
There was no response.
He moved a little closer and said again, "Honey, can you hear me?"
Still, there was no response.
Finally he moved right behind her and said, "Honey, can you hear me?"
She replied, "For the third time, Yes!"