This is Bird No.

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

And why don't other birds wings hum and 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 wingbeats.

When hummingbirds flap, they create lift both on the downstroke and the upstroke, so twice

per wingbeat.

The researchers found that the hum derives from the difference in air pressure between

the top and 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 woosh, but only a hummingbird's hum.

For Bird Note, I'm Ariana Rimmel.

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