Natural frequency and resonance
Strike a bell, a glass or a tuning fork and it rings at particular pitches. Those are its natural (resonant) frequencies. They depend on the object's shape, size, mass distribution and the stiffness of its material. A periodic push that matches a natural frequency transfers energy efficiently, so the vibration builds up until losses balance the input.
Key quantities
- Frequency (f): cycles per second, in hertz (Hz).
- Quality factor (Q): how sharply peaked the resonance is; high Q means low damping.
- Mode: a specific vibration pattern with its own frequency.
Why frequency is a good thing to measure
Frequency can be measured very precisely against a stable clock, so small shifts in a resonance can be detected. The same property makes it sensitive to temperature, mounting and other disturbances, which must be controlled or recorded.
Resonance in S.P.H.E.R.E.
The proposed experiment compares the measured resonant frequencies of controlled copper spheres at different locations. Whether any location dependence exists is the hypothesis being tested, not an established result. Next: vibration modes of a sphere. Background: Wikipedia: Resonance.