4. Sensitivity to mechanical environment

The resonator is a vibrator whose frequency can vary if the propagation speed or resonance conditions vary. Linear relations, i.e. first-order development of deformations, perfectly describe a wave of negligible amplitude in an unconstrained medium. However, this approximation fails in two main cases:

• propagation of a high-amplitude wave, whose behavior will explain phenomena linked to the excitation level (anisochronism, intermodulation of resonators and filters, etc.);

• propagation of a low-amplitude wave in a constrained medium, the analysis of which will help explain the mechanisms of frequency variation under mechanical constraints (acceleration, pressure, etc.).