It turns out that humming may help in the perpetual struggle against sinus infections:
In a study in The American Journal of Respiratory and Critical Care Medicine, researchers examined this by comparing airflow in people when they hummed and when they quietly exhaled. Specifically, they looked to see if humming led to greater levels of exhaled nitric oxide, a gas produced in the sinuses. Ultimately, nitric oxides during humming rose 15-fold.
This blogger is eager to find out if singing AC/DC songs at the top of his lungs while driving has some sort of health benefit as well. Though this health benefit would have made itself apparent many years ago already.