Brainstem auditory evoked potentials (BAEP) are the electrical activity of nerve impulses in the auditory conduction pathway of the brainstem induced by sound stimuli. It is generally believed that the possible sources of each wave are: wave I, the extracranial segment of the auditory nerve; wave II, the intracranial segment of the auditory nerve and the cochlear nucleus; wave III, the medial superior olivary nucleus or the cochlear nucleus; wave IV and wave V, the lateral thalamic nucleus; wave V may still be related to the electrical activity of the central nucleus. Test indexes: The absolute latency (PL), interpeak latency (IPL), V/I wave amplitude ratio and V wave response threshold of BAEP main waves I, III and V were mainly measured. In the conventional test, the first 5 waves such as wave Ⅰ to wave V are the most stable, among which wave V has the highest amplitude and can be used as a marker to identify each wave of BAEP. Under normal conditions, wave Ⅱ and wave Ⅰ, or wave VI and wave VII often fuse to form a composite waveform. Judgment criteria: Normal criteria:Both ears have typical image curves, complete waveforms, clear differentiation, good repeatability, and 100% wave out rate of Ⅰ, Ⅲ and V main waves, PL and IPL in the normal range of the same age in this laboratory. Therefore, the examination results do not only look at the V wave response threshold, but also must refer to Ⅰ, Ⅲ, V wave absolute latency (PL), interpeak latency (IPL), V/Ⅰ wave amplitude, in order to make a correct judgment conclusion. Abnormal criteria: According to the absence of Ⅰ, Ⅲ, V wave, PL, IPL and V wave response threshold is greater than 3.0 standard deviations under the same test conditions of this experiment. Types of abnormalities: (1) peripheral auditory pathway damage: mainly refers to Ⅰ wave absence or PL prolongation and V wave threshold elevation. (2) Central brainstem auditory pathway damage: mainly refers to the absence of Ⅲ and V waves, prolongation of PL and IPL or V/Ⅰ wave amplitude ratio.