A hearing test that analyses brain waves for subconscious responses to sound has recently

been devised by a team of specialists at the University of Iowa. Instead of depending on the patient to indicate when he hears a laboratory-controlled noise, as in the traditional form. of testing, this new method, called electric response audiometry, enables audiologists to trace the noise's path directly from the ear to the brain while the patient relaxes or sleeps. Although brain responses have been used in other auditory tests for some time, the University of Iowa specialists are the only scientists to date who analyze simultaneously three components of hearing—the responses of the middle ear, the auditory nerve, and the brain stem. This information helps to identify the precise location of a hearing problem and, at the same time, to measure its severity. While electric response audiometry is not meant to replace conventional means of testing, it is specially effective in diagnosing hearing problems in very young children, multiply handicapped individuals, and psychologically disturbed persons because it does not require the patient's active participation.

According to the passage, electric response audiometry can be used ______.

A．whether a person is awake or asleep

B．only if a person is relaxed

C．particularly if a person hears a loud noise

D．particularly when a person is dreaming