What does ringing a bell mean:

Bells are used to call the faithful to worship & toll the time. The sound of a bell can express great joy, sound a warning, or signal great loss and mourning. Bells have also been rung to bring on or stop the rain, keep evil spirits at bay,invoke curses, and lift spells.

Bells hold an honored place in religious ceremonies. In both Buddhism and Christianity, bells are blessed before each ceremony. In Roman Catholicism, bells are symbols of paradise and the voice of God. According to Tibetan Buddhism, ringing the bell represents an offering to all the buddhas and bodhisattvas in order to accumulate positive karma. Also, the bell represents wisdom, so ringing the bell is the sound of wisdom which purifies confusion.