400Hz (400-cycle) aircraft APU mains hum. Heard in the cabin and cockpit of large passenger airplanes. The 400Hz AC electric supply is used to power all onboard lighting, …
April 28th, 2024
This is the sound of an AC ground power unit mounted under a jet bridge at an airport. In the sound, it turns on, turns off, stays on, …
British telephone busy signal generated in Audacity with 400Hz tone
January 3rd, 2015
a 400Hz -18dBFS 30 second line up tone line up tone.
UK
September 18th, 2014
Example of the British-style telephone ringing tone, namely 400hz and 440hz in a 0.4, 0.2, 0.4, 2.0 sequence, repeated several times.
400hz sine wave sound
June 17th, 2010