Roof tiedown noise

Bought a used canoe, love it. When carrying it on the roof there is a howl starting at 40MPH that makes fingernails on a blackboard soothing. Any suggestions how to quiet the straps down?

Put a twist or two in the strap where a section is free running and exposed to the wind

And keep
the straps close to the gunwales where they pass under the crossbars.