In
physics and
engineering the
quality factor or
Q factor is a
dimensionless parameter that describes how
under-damped an
oscillator or
resonator is, and characterizes a resonator's
bandwidth relative to its center frequency. Higher
Q indicates a lower rate of energy loss relative to the stored energy of the resonator; the oscillations die out more slowly. A pendulum suspended from a high-quality bearing, oscillating in air, has a high
Q, while a pendulum immersed in oil has a low one. Resonators with high quality factors have low
damping so that they ring longer.