Why does Tom Waits' voice sound the way it does?

Question

Do singers like Waits achieve a "gruff" vocal sound by some sort of technique, or is it just from smoking a lot?

Answer 1

Tom had this to say in an interview:

"I bark my voice out through a closed throat, pretty much"

http://www.wbur.org/npr/141657227/tom-waits-the-fresh-air-interview

Answer 2

The smoking didn't hurt, but it's a vocal technique. Check out Captain Beefheart and Howling Wolf. They were both influences to his vocal style.

Captain Beefheart

Howlin' Wolf

Answer 3

It could be HPV (human papilloma virus) which can in a small percentage of men attack the vocal chords. Instead of vocal cords that resemble violin strings, HPV turns them into jello, making clear crisp sounds difficult.