Mystery Drone

I’m getting a droning noise when driving. To clarify, it only starts around or above 40mph never below and only when under power. If I touch the accelerator I get the drone, if I let off it goes away. I get it ONLY with the accelerator being pressed above 40mph, no other times at all. Can’t figure it out therefor I am a new member of StangNet... Thanks in advance. 2001 Mustang GT convertible. Also the frequency of the drone increases with speed.

It does sound like it’s coming from the rear but sometimes it’s hard to tell. I was thinking it might be the rear end as well but I really don’t know enough to say for sure. I’m willing to bet you’re 100% right though. Thanks for the info, I really appreciate it. Looks like i’m gonna be rebuilding the rear end.