I have never, over the course of a dozen+ boat toting vehicles, had a bow line to bumper, or even diagonally vee’ed lines to under-hood tiedowns, make any noticeable noise.
Likewise I have never had traverse belly lines sing. That said, always lines. Ropes not straps. Even with an anti-harmonic thrum half twist webbing can sing a bit with the right aerodynamics and speed. The lines are low-stretch, start as tight as I dare with a trucker’s hitch, and get checked/tightened if necessary every time I stop for gas; there isn’t a lot of slack to vibrate thrum.
Maybe I’ve just been vehicle-lucky; including 3 trucks, 3 vans, two small SUV’s and a couple or five sedans, but I have yet to have a roof rack itself make an iota of whistle or thrum.
I am an auditory driver, I have to have my window open at least a crack so I can hear what’s going on around me. Worst drive I ever endured was with Wenonah’s rattleclanky aluminum plate adjustable seat hangers, positioned on the van just behind the driver’s seat. Arrrggghhhh, 100 miles of that was all I could stand.
I wedged a bunch of rags (including, IIRC, my socks) in between the rattling seat and hull edge. That helped a lot, and when we got home I wedged & glued a piece of minicel in there.
Rack, strap, line or boat noise would drive me bat crap behind the wheel.