The nagara (sounding of drums, symbols, bells, etc) invites all the devs to the aarti, so they can have the darshan of the Supreme Lord. In much the same way, the gantadi (bell) is rung in temples and homes to tell everyone that aarti is taking place so they too can have this divine darshan. The divine sound overpowers any other noise and helps to focus our senses on the Lord.