For babies who do not pass the newborn hearing screening, they need to go to a qualified hearing diagnostic institution within 3 months of age for hearing diagnosis, in which the first and foremost is the hearing test, including acoustic conductance (1000 Hz), otoacoustic emissions and auditory brainstem response (multi-frequency steady-state evoked potentials should be added when the auditory brainstem is unresponsive). Acoustic immittance test: It is of great value for the localization and diagnosis of middle ear lesions, and combined with the pure tone hearing threshold test, it can make a preliminary quantitative, qualitative and localization diagnosis of hearing loss. It is also one of the most basic tests required in audiological diagnosis. Oto-acoustic Emissions: An indicator of the function of the outer hair cells of the cochlea. It is mainly used to assess the loss of auditory function in the cochlea. Auditory brainstem response: Useful for localizing and diagnosing lesions in the auditory pathway from the auditory nerve to the brainstem. The response threshold through the V-wave helps in the objective assessment of the level of hearing loss. Auditory steady-state response: It can be used to determine the presence or absence of residual hearing in children with severe deafness by high-intensity stimulation (120 dB nHL), which overcomes the limitations of tbABR in terms of high-intensity elicited non-response.