When I look at 2002 Bounders online I see two basic configurations of the front end. One has a grill and the other does not have a grill at all. Which type do you have?
If it has a grill I would try taping a sheet of cardboard over half the grill and then drive it briefly. If the speed the whistle occurs at changes it will tell you it's caused by air going into the grill.
Maybe you've already done this but I would tape up any and every line and joint on the front and drive again to see if it changes.
Could it be caused by the windshield wipers in the air stream? That could be checked by running the wipers while it's whistling, or temporarily take the wiper arms off completely.
Could the sound be caused by airflow around the drivers side headlight, turn signal or fog light? Heck maybe try taking the license plate off.
I wonder if the sound could be caused by something on the front side. Maybe put a ball of tape over the front of the rain gutter drip rail to break up the airflow. Maybe run a strip of tape around the window on the drivers side.
If your husband is handy try removing the drivers side mirror and tape up the hole(s) left behind. It's possible the shape of the mirror itself is causing the whistle.