According to a New York Times story here, humming isn't just entertaining, but it could be good for you:
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.
Another study a year later in The European Respiratory Journal found a similar effect: humming resulted in a large increase in nasal nitric oxide, “caused by a rapid gas exchange in the paranasal sinuses.” Since reduced airflow plays a major role in sinus infections, the researchers suggested that daily periods of humming might help people lower their risk of chronic problems. But further study is needed, they said.
THE BOTTOM LINE
Studies show that humming helps increase airflow between the sinus and nasal cavities, which could potentially help protect against sinus infections.
But why wait for another study?