Unless you are talking about an electric toothbrush, vibrations are generally an undesirable by-product of industrial activity or environmental action. All sorts of ill effects are associated with vibrations: noise, discomfort, stresses, material fatigue, etc; eventually, vibrations tend to result in decreased efficiency, higher maintenance costs, and shortened life of equipment and structures.

Common sources of vibration are traffic of pedestrians or vehicles, excitation by winds or waves, the operation of pumps and other mechanical equipment, explosions, earthquakes, impacts…

In fact, just circulating fluids can cause vibrations, particularly when phase changes are involved. And the mechanisms are sometimes sophisticated: imagine the frequency of the von Karman eddies coupling with the second cantilever mode of a lamppost, or the excitation from collapsing bubbles of liquid salt, or the unconscious synchronisation of active audiences or pedestrians.