How Does a Handpan Work?
Entire books have been written on the subject of tone generation in tuned steel. This article is only meant to be a brief overview.
The handpan consists of two steel bowls joined at their edges. There is nothing inside of the instrument that makes it sounds the way it does. Sometimes, baffles may be used to control undesireable frequencies, but that will be left for another discussion.
Handpans and similar instruments work on a very unique principle of compressive in-plane stress.
It is a common misunderstanding that the ‘notes’ or ‘tone fields’ on a handpan are under tension, like the skin on a drumhead. However, it is quite the opposite.
In fact, the metal within the tone field is under a compressive stress; the metal within the tone field is actually pushing out against the border in all directions. This creates a state of controlled buckling, similar to metal lids seen on mason jars.
In order for the tone fields to sound pleasant to the ear, some vibrating modes are forced into the note by the tuner. These frequencies are most comonly an octave of the fundamental pitch (the octave being two times the fundamental pitch), and then a second harmonic commonly tuned to a compound fifth (three times the fundamental pitch).
It is this harmonious relationship of frequencies in each note that makes the unique sound of tuned steel that so many people love and crave.