I can’t figure out if this is a silly question or not - so I’ll ask it anyways. Do the deaf hum or whistle? There’s no reason why they wouldn’t be able to, physically, and no reason why musical understanding (such as rhythm or beat or whatever) couldn’t be understood. So do they? It would seem to me that one would be able to “feel” whats being hummed or whistled, and so he/she might still do so, even if they can’t hear it. Anybody?
I’ve heard deaf people hum. I don’t know about whistling, but I don’t see why not. 
A couple years ago there were many young people walking around shopping centers here handing out cards saying they were deaf and basically soliciting donations. After I turned down one, she walked away whistling.
I took the more cynical interpretation of that.