A BAER test, an acronym for brainstem auditory evoked response, detects electrical activity in the cochlea and auditory pathways in the brain in much the same way that an antenna detects radio or TV signals or an EKG detects electrical activity of the heart.
The response is collected with a special computer through electrodes placed on the scalp and earlobes. The stimulus click produced by the computer is directed into the ear using headphones. Each ear is tested individually, and the test usually is complete in 10-15 minutes. A printout of the test results should show spikes in your brain activity each time you heard one of the clicking sounds or other tones.