Why do Hindus ring bells in temples?

The answers to that question are given in the old vadic texts and shastras.

There are spritual and scientific reason behind ringing bells. Ringing of bells has many health benifits too.

When being rung, its vibrating sound will instantly ward off any negativity in temple vicinity.

When bells ring a vibration is created in the atmosphere.

All the bacteria, microbes, and other harmful microscopic germs falling on the path of these vibrations get distroyed.