Hum

Here's something I definitely did not know. When you breathe through your nose, not your mouth, your nasal passages produce nitric oxide which aids in how we absorb oxygen into the body. While checking this out online I stumbled across the article linked below which states that when you hum while exhaling through your nose there is an increase in the nasal production of nitric oxide by 15 fold.

ATSJournals: Humming Greatly Increases Nasal Nitric Oxide