Question Arising from Recent Fanfic

Do a lot of people, or at least a lot of fanfic writers/readers, consider humming particularly sexy, or something? There seems to be a convention of men humming seductively as they kiss somebody, or gaze into another’s eyes, or just pause in the conversation.

Maybe it’s not literal humming, maybe it means the character is saying “hmm,” or making some inarticulate sound that can’t be accurately conveyed as a grunt or a sigh?