He didn't - it's just part of the act (makes people pay more attention). He has a beautiful speaking voice offstage.
Narrative voice is the words and how they are put together; the narrative voice is the teller's voice.
You Lose Your Voice
The only way possibly to lose your voice is by either yelling loudly, or going through your period where your voice intends to change its pitch. It is in this time that you are likely to lose your voice for a short period of time. but to lose your voice for a prank is not possible.
The voice for Mr.Fox is George Clooney.
Gilbert Gottfried was the voice of Mr. Mxyzptlk .
Tom Kenny is the voice of Mr. Lopart on Handy Manny.
The medical condition where you lose your voice is called laryngitis. This is an inflammation of the voice box and often mimics the common cold until you lose your voice.
They lose there say, they lose there voice in society!
The voice of Mr. Potato Head is Don Rickles.
According to http://www.raybromley.com/guf/miscGUF.html the average teller loses $250 each year.
The voice of Mr. Krabs is Clancy Brown