There are a few ways that you can reduce wind noise in your cargo box. One way is to make sure that the box is properly sealed. You can use weatherstripping or other materials to help create a seal around the lid of the box. Another way to reduce wind noise is to add insulation to the inside of the box. This will help to deaden any sound that might be coming from outside of the box. Finally, you can also try using a tarp or cover over the top of your cargo box when it is not in use. This will help to further reduce any wind noise that might be emanating from the box.