Infant in a U.S. hospital undergoing tests for hearing impairment using auditory evoked potential. The device, the Nicolet Pathfinder, measures the tiny changes in the brain's electrical activity brought about by auditory stimulation. The stimuli are applied through the baby's headphones, and an electroencephalograph (EEG) records the brain's electrical response. The results are processed by computer, removing background details, and averaged out. By comparing the characteristics of the output (seen on screen) with normal results, any problems may be identified.