Acoustic Resonance

I followed a clear ringing sound further down the stone walkway until I spotted a metal wind chime hanging from a low tree branch. Standing on an overturned terra-cotta flowerpot, I reached up with a dry twig I retrieved from the grass. I tapped the longest aluminum tube right near its base. It produced a deep, sustaining tone—acoustic resonance generated by standing sound waves in a hollow cylinder! I tapped each adjacent pipe in succession, watching how varying lengths shift the pitch higher. The vibration tickled straight through the little wooden twig in my paws.