Sound Pillar

A rectangular black granite pilar about 1500 milimeters heigh, with for slits running from across the top to three quarters of the way down the sides. The pilar sits on concrete and is located in a garden environment.

While solid objects vibrate to create sound, air gaps help to generate louder sounds.

How it works

Knock around the top and sides of the pillar and listen carefully for the subtle sounds you create.

Things to try or ask around the exhibit

Would the pillar sound different if it had no gaps at all?
Does it matter whether you tap on the top or the side of the pillar?

Background

The Sound Pillar is a solid block of black granite, with a deep cross carved down the centre of the pillar. When you tap on the solid pillar, it vibrates slightly, causing neighbouring particles within the pillar to vibrate as well. Once a vibration reaches the cross in the centre of the pillar, the vibrations move back and forth more vigorously, allowing you to hear the sounds more clearly (although they're still quite subtle in volume).

Finding the science in your world

Percussion instruments used by musicians contain a variety of different sized hollows, to generate softer or louder sounds, and to create different tonal qualities which are referred to as 'timbre'.