Along with influence from photography, the arts, music, I think one aspect has been overlooked. The radio programmes of the 40's and 50's. Shows like 'Yours Truly, Johnny Dollar' and 'The Whistler' seemed to have undertones like the films noir of the time. Albeit, being a serial, these shows didn't go as deep as the movies did. I believe they did, however, display the characteristics of noir. The stories, the characters, the use of sound and music. The major difference being the visual and the mood that the cinematography normally made, was left to the imagination of the listener.