What is the meaning of "The size of adam's apple"?

Answer 1

Ok I know I'm stating the obvious, but just in case this is what you're looking for:

The Adam's apple is
"the slight projection at the front of the throat formed by the largest cartilage of the larynx, usually more prominent in men than in women",
i.e. it's simply the lump at the front of your throat.

I don't know that its size means anything else than literally how big or small it is.
Some people don't like the size of their Adam's apple and have it changed by plastic surgery, though that is quite dangerous...

Answer 2

It may refere the strength of sound of somebody ...