An electroacoustic instrument designed to evaluate the activity of the auditory pathway of the brain in response to an acoustic signal [auditory brainstem response (ABR)] it provides at the ear (e.g., clicks delivered through an earphone), without need of patient cooperation. The signal, detected via the device's scalp electrodes and possibly a reference electrode on the ear lobe, is measured using computer averaging and signal processing techniques. This device is typically used to assess the function of the auditory pathways and to differentiate coma due to metabolic factors from structural damage.