the.com/hum
the sound you make when your brain forgets the words but refuses to shut up
earth's noteThe planet hums a constant low frequency below human hearing
power linesThey drone at 50 or 60 hertz, depending on country
the humA mysterious global noise some people hear, others never can
hummingbirdsNamed for the wing-hum, beating up to 80 times per second
focus trickHumming raises nasal nitric oxide, easing airflow and stress