• Oscillations
  • The process of regularly varying pressure above and below a mean value, a periodic process. 
Abstract from DBPedia
    Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. The term vibration is precisely used to describe a mechanical oscillation. Familiar examples of oscillation include a swinging pendulum and alternating current. Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science: for example the beating of the human heart (for circulation), business cycles in economics, predator–prey population cycles in ecology, geothermal geysers in geology, vibration of strings in guitar and other string instruments, periodic firing of nerve cells in the brain, and the periodic swelling of Cepheid variable stars in astronomy.

    振動(しんどう、英: oscillation、vibration)とは、状態が一意に定まらず揺れ動く事象をいう。英語では、重力などによる周期が長い振動と、弾性や分子間力などによる周期の短い振動は別の語が充てられるが、日本語では周期によらず「振動」という語で呼ばれる。周期性のある振動において、単位時間あたりの振動の数を振動数(または周波数)、振動のふれ幅を振幅、振動の一単位にかかる時間を周期という。

    (Source: http://dbpedia.org/resource/Oscillation)