Altar Bell              

The bell is a feminine symbol, often used to invoke the Goddess in ritual. It is a ritual instrument used for releasing powerful vibrations relative to their volume, and tone, reflecting the element of Air. A bell or gong can be rung to banish unwanted entities, negativity or anything else you do not wish to remain in your area. The gentle vibrations and tones purify your ritual area. It can be rung to signify the beginning or ending of a ceremony or ritual but remember that once rung it can not be undone. It is used in Dragon Magick to attract the dragon at a certain point in a ritual. It is also a way to focus your mind at a certain point in rituals too.

Alternately, as touched on, you could use a small gong or finger symbols or even a triangle to represent this form of air.

What kind of bell do you choose? A Tibetan bell with dorje? A small bell with its own clanger? The choice is yours, the only advise I would offer you is be guided by the tone when it rings. You'll know when you find the right one!