Like Tyflyer said, twist the straps a few times. The buzzing didn't hurt the kayak because the buzzing is from the part of the line that isn't touching the kayak. Make that part of the line (between the car and kayak) twist/turn on itself a few times. Also, if you tie the kayak down in front, too, you won't have to crank down so hard on the side straps. Twist that one, too.