Striking a metal rod can create sound. How the rod emits sounds may depend on various factors, such as the way the rod is supported, material used to hit the rod, etc. But carefully listening to the sound we notice that there is a component with the lowest pitch.
Say the rod is of:
- length (L): 100mm = 0.1m,
- radius (R): 10mm,
- Young’s modulus (E): 197GPa,
- Poisson’s ratio (): 0.3,
- density (): 8000Kg/m^3.
Then wave velocity in the rod should be something like
Assuming free vibration (no fixed boundary), wave length of the fundamental mode should be
Its frequency is then
The frequency is way beyond the upper limit of my hearing. So I am hearing sub-harmonics, or what?