1.Pure tone audiometry Pure tone audiometry is referred to as electroacoustic audiometry, which uses the principle of electroacoustics to generate pure tones of different frequencies and intensities, and to determine the degree and type of deafness and the location of the lesion by testing the hearing threshold strength of each frequency in the examined ear. Pure tone audiometry is one of the most accurate and commonly used methods in clinical audiology that can be both qualitative and quantitative. Because it is a subjective audiometric method, the accuracy of its test results is affected by many factors, such as the test environment, the degree of cooperation of the test subject, the calibration of the audiometer, the operation of the examiner, and the condition of the external auditory canal. 2.Acoustic conductance test The acoustic conductance test is performed by measuring the change in acoustic impedance of the middle ear, and then recording it to provide an objective basis for analyzing middle ear pathology. It is one of the routine methods for clinical hearing diagnosis because of its high sensitivity, easy operation, objective results and high accuracy. It is mainly used to identify the nature of deafness, the site of deafness lesions (such as cochlear lesions and postcochlear lesions), identify non-organic deafness, provide diagnostic reference for postcochlear auditory pathways and brainstem diseases, make localized diagnosis and prognosis prediction for peripheral facial palsy, and make auxiliary diagnosis and efficacy assessment for myasthenia gravis, etc. 3.Auditory brainstem response audiometry (ABR) is the detection of brainstem bioelectric response evoked by acoustic stimulation, consisting of several waves, also known as brainstem auditory evoked potentials (BAEP). By measuring the waveform, amplitude and latency, it can objectively and sensitively reflect the function of the brainstem and the degree of hearing impairment. It is mainly used clinically for: determination of high frequency hearing threshold, hearing screening of newborns and infants, identification of organic and functional deafness, diagnosis of occupying lesions in the pontocerebellar horn, etc.; it can provide valuable objective information for diagnosis, localization and treatment selection, outcome judgment of central nervous system diseases such as auditory neuropathy, multiple sclerosis, brainstem glioma, traumatic brain injury, coma, cerebral palsy, brain death, etc. 4.Otoacoustic emission Otoacoustic emission is divided into spontaneous otoacoustic emission (SOAE) and evoked otoacoustic emission (EOAE) according to the presence or absence of external acoustic stimulation. The latter is divided into transient evoked otoacoustic emissions (TEOAE), distortion product otoacoustic emissions (DPOAE) and frequency stimulated otoacoustic emissions (SFOAE) according to the type of stimulation. Otoacoustic emissions are closely related to inner ear function, and any factor that impairs the function of the outer hair cells of the cochlea causing hearing impairment above 40 dBHL can lead to a significant reduction or loss of otoacoustic emissions. This is the theoretical basis of otoacoustic emission as a hearing screening method. Otoacoustic emission testing has the advantages of being objective, simple, non-invasive and sensitive. Clinical applications: hearing screening of infants and children, early quantitative diagnosis of cochlear deafness (e.g., drug-induced deafness, noise deafness, Meniere’s disease, etc.), differential diagnosis of cochlear deafness and postcochlear deafness, and determination of postcochlear auditory pathway lesions.