This is Bird Note.

Just what puts the hum in a hummingbird's wings.

And why don't other birds' wings humming birds' wings hum in flight?

To figure it out, scientists used a specially built rig to measure air pressure,

12 high-speed cameras, and over 2,000 microphones to observe hummingbirds

fluttering in place at an artificial flower. This allowed them to make 3D visualizations

of the sound of a hummingbird's wing beats. When hummingbirds flap, they create lift both on the downstroke and the upstroke, so twice per wing beat.

The researchers found that the hum derives from the difference in air pressure between the top and the bottom of the wings,

which alternates 40 times a second as the hummingbird flaps.

The rapidly shifting air pressure produces a harmonic set of sounds, from low to high, creating

that iconic, musical hum.

Other birds flap with power on the downstroke only, so there's no rapidly changing pressure difference when they fly,

making them much quieter. Their wings might whoosh, but only a hummingbirds hum.

For bird note, I'm Ariana Rimmel. a rebel.