Soundscape: Paranal UT chiller

(Interior) Fan sounds are very characteristic at the telescopes’ enclosures. This sound corresponds to the air conditioning inside a Unitary Telescope (UT), an active thermal control during the day that keeps the area at 5-11°C, as this is the average exterior temperature for the beginning of the night. Telescopes are kept at this temperature in order to avoid turbulences (caused by difference in temperature) in the air inside the telescope after the opening.