A bell was a device used to produce sound.
A ghanta was a type of Tibetan bell. (TV: The Abominable Snowmen)
On Mondas, the Fifth Doctor rang church bells to alert the people to the grave robbing that was going on. (AUDIO: Spare Parts)
The crew of the Valiant were lured to a door which led to Time's End by the sound of a train bell. (AUDIO: The Nowhere Place)
The Eighth Doctor was once locked in a room full of ringing bells on Caerdroia. (AUDIO: Caerdroia)