Drove my wife's car on a long trip.

When I went over 70 MPH, i got this strange vibration noise coming from the
driver's side dashboard.  hi-pitched, only occasionally. road conditions
didnt seem to affect it, only speed.

i tried touching certain items, but it wasn't affected.

closest description is the sound a comb makes when you put tissue paper over
it and blow. used to do that as a kid (40 some years ago).

any thoughts?