The Physics of Vibration

Kurzfassung

Vibrations are mechanical oscillations. They can be described by frequency, amplitude, phase and shape. There are several ways to describe amplitude, and these different terms cannot be used interchangeably. Moreover, each of these terms indicates different physical properties of the vibration signal, and thus has different relevance for benefits and risks by vibration exercise and therapy. Vibrations can naturally emerge in systems that allow transfer between different types of energy, e.g., between potential and kinetic energy (pendulum) or between elastic and kinetic energy (spring-mass oscillator). Driven vibrations are generated by actuators that impose their own frequency onto another system. Resonance occurs when an actuator excites a natural oscillator at its preferred frequency, the so-called eigenfrequency. Analysis of oscillatory signals has traditionally been performed with spectral analysis, which is based on Fourier’s harmonic analysis. More recently, wavelet analysis has been proposed for time-variant signals. A third opportunity is offered by averaging methods, such as peri-stimulus plots and peri-stimulus histograms, in particular when the shape of complex oscillations is of interest.