The bullroarer is an ancient ritual Aboriginal musical instrument and a device historically used for communicating over great distances. In Australian Aboriginal culture, it is used in religious rituals and ceremonies, such as initiations and burials, to communicate over distance, and sometimes to ward off spirits. 

It consists of a piece of wood attached to a string or twine, which when swung in a large circle produces a roaring vibrato/humming sound. Bullroarers have been used in initiation ceremonies and in burials to ward off evil spirits, and for bad tidings. Bullroarers are considered secret men's business by all or almost all Aboriginal tribal groups, and hence forbidden for women, children, non-initiated men, or outsiders to even hear.