4cylinder Rav4, strange noise accelerating and decelerating around 40 mph. Lightly moist roads mist / fog. Sound lasts for 3 - 5 seconds each time. Dealer found nothing wrong. Issue happen one more time after leaving dealer. Toyo Open Country A20 Tires in good shape. Issue has not happened the last day or so. Any ideas? Is this just a Rav thing ?