side windows whistle on 2013 sightseer 33c

Your "problem" is most likely the weep holes for the windows. Look at the outside of the window at the bottom. You'll see two slits in the metal frame. These slits are to allow water to drain outside the window instead of inside. Many mfg put covers on these slits to prevent the whistling. As a trial, take a small piece of duct tape and place it on all the window slits. See if the whistling goes away. If it does then you'll have to buy the little covers that go over them. Do not leave the duct tape on the slits or you could develop a water leak....Dennis

Weep hole cover