1. A buzzing or clicking sound in the back of the head which is experienced by someone who is subjected to pulsed microwave radiation; such as, from a skull to voice instrument. 2. The sensation of hearing which is produced when an alternating current of suitable frequency and magnitude is passed through an animal or human body.
3. Audible clicks induced by pulsed or modulated microwave frequencies.

The clicks are generated directly inside the human head without the need of any receiving electronic device.