Why do Hindu temples have Bells?
It is believed that deities remain manifest in mandirs in which bells (ghanta) are rung. In Hindu mandirs, bells are usually hung in the area or porch preceding the inner sanctum. Devotees ring them as an invocation to the deity to listen to their prãrthnã and be blessed.
There is an art and science of making bells to produce the requisite sounds. There are bells specially made to produce the long strains of the sound OM. The handle of a ghantadi signifies prãna – the vital force in the form of Hanumanji, Garud, Nandi or Chakra. During Garud sthãpanvidhi, the handle is offered pujan. A bell without a handle in one of these forms is forbidden in rituals, since it may augur misfortune. The body of the bell is said to represent the divinity of time (Ãgama-Kosha 1992 VI:99). (Source:kids.baps.org).
Here is a deep scientific analysis of the temple bells.
Bells are also used to inform people to gather for aarti too.
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