The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague. Commonly heard when a train passes a stationary person, Mechanical,
A background ambience, suitable for a machine room or furnace room. A heating or engine or machine is running, giving a constant hum and buzz. Seamless looping! Mechanical,
