Audiometric testing procedures are used to diagnose hearing disorders.These tests include:
- Tone threshold audiometry – tones of different frequencies with different volumes are played and the volume is determined at which the patient can just hear the tone of the respective frequency; furthermore, sound conduction is performed by air and bone conduction, this allows a distinction of disorders of the inner ear or middle ear.
- Impedance measurement – measurement of the acoustic impedance of the eardrum (part of the sound waves reflected by the eardrum). The resistance changes with the tension of the eardrum and is a measure of the mobility of the eardrum.
- Distortion products of otoacoustic emissions (DPOAE) – inner ear function testing.
- Speech audiometry – examination of hearing in terms of perception and intelligibility of speech.
- Dichotic speech test – testing of central auditory processing in adults and children (from about 5 years).
- Binaural Masking Level Difference (BMLD) – detection of disorders of the central auditory pathway.
These tests can be used to determine whether hearing loss is more likely due to changes in the hair cells of the inner ear or neurodegenerative changes in the central auditory pathway. In age-related hearing loss, a combined disorder of hair cells and central auditory pathway is present in about half of the cases.
