Why do we ring the bell in a temple?

Is it to wake up the Lord? But the Lord never sleeps. Is it to let the Lord know we have come?
He does not need to be told, as He is all knowing. Is it a form of seeking permission to enter
His precinct? It is a homecoming and therefore entry needs no permission. The Lord
welcomes us at all times. Then why do we ring the bell?
The ringing of the bell produces what is regarded as an auspicious sound. It produces the
sound Om, the universal name of the Lord. There should be auspiciousness within and
without, to gain the vision of the Lord who is all-auspiciousness.
Even while doing the ritualistic aarati, we ring the bell. It is sometimes accompanied by the
auspicious sounds of the conch and other musical instruments. An added significance of
ringing the bell, conch and other instruments is that they help drowned any inauspicious or
irrelevant noises and comments that might disturb or distract the worshippers in their
devotional ardour, concentration and inner peace.
As we start the daily ritualistic worship (pooja) we ring the bell, chanting:
Aagamaarthamtu devaanaam
gamanaarthamtu rakshasaam
Kurve ghantaaravam tatra
devataahvaahna lakshanam
I ring this bell indicating
the invocation of divinity,
So that virtuous and noble forces
enter (my home and heart);
and the demonic and evil forces
from within and without, depart.