For audience, the main type would be males, usually older. This may be because most Noir films are quite old and would offer a sense of nostalgia for the older viewers.
It could also be because there is a little bit of action, and crime involved therefore stereotypically appealing to males. Another reason would be the introduction to an attractive femme fatale, and the male viewers would enjoy seeing a beautiful woman portrayed usually erotically or sexually.
This being said females will still watch them however they will tend to view more neo-noir.
