In Hindu religion, outside the temples and shrines, bells are hanged. It is believed that in a temple where the sound of the bell is heard clearly, such temples are called Jagrat Dev. It is known that in temples, every morning and evening aarti takes place and at that time apart from ringing many small bells, large bells are also used.
The point is very few people are aware that hanging bells in a temple not just has spiritual, but also scientific reasons.
The bells in temples are played/used in a specific rhythm and pace. It is believed that by ringing bells in a temple, the gods in the form of statues wake up and the wishes of devotees are fulfilled sooner.
According to the Skanda Purana, by ringing the bells in a temple, the sins of humans hundred lives are removed. Bells are believed to be the symbol of Kaal. According to Dharam Shastras, when the time of destruction will come, sound of millions of bells ringing will be generated.
There is a scientific reason too behind hanging bells in temples. When bells ring, a vibration is created in the atmosphere, which spreads too far with the flow of winds. All the insects and particles coming across this vibration get killed and the atmosphere becomes clean and healthy.