15.15: Caractéristiques de la résonance
If a driven oscillator needs to resonate at a specific frequency, then very little damping is required. For example, piano strings require little damping to be played. Conversely, to achieve small-amplitude oscillations, such as in a car's suspension system, heavy damping is required. Heavy damping reduces the amplitude, but the tradeoff is that the system responds at higher frequencies. For instance, speed bumps and gravel roads prove that even a car's suspension system is not immune to resonance. Despite highly engineered shock absorbers, which convert mechanical energy to thermal energy almost as fast as it comes in, speed bumps still cause a large-amplitude oscillation. On gravel roads that are corrugated, the bumps are very noticeable if a car travels at the wrong speed; on the other hand, when driven at the correct speed, the bumps are hardly felt.
These features of driven harmonic oscillators apply to a huge variety of systems. When a radio is tuned, for example, its resonant frequency is adjusted so that it only oscillates to the desired station's broadcast (driving) frequency. The more selective the radio is in discriminating between two stations, the smaller its damping. In all of these cases, the efficiency of energy transfer from the driving force into the oscillator is best observed at resonance.
This text is adapted from Openstax, College Physics, Section 16.8: Forced Oscillations and Resonance and Openstax, University Physics Volume 1, Section 15.5: Forced Oscillations.
