Strange Rattle

[Nhdataguy]

At freeway speeds I can hear a strange rattle that sounds like someone is ringing a tiny bell in the section right by the front seatbelt? I was driving and My son in law heard it, I could not, then last few days I was in passenger seat and could hear it. I put my ear up to the panel and that's where its coming from. I don't think its speed related but maybe highway speed related?
I would say that its like there was air coming in the bottom of the door and vibrating something?
Anybody else hear something like this?

Thanks