The X-axis in an audiogram represents the frequency of the test tone, typically from 125 Hz to 8 kHz (up to 16 kHz for high-frequency audiometry). It is logarithmically scaled to clearly represent the wide hearing range of the human ear and to visualize tonotopia. Each point on the X-axis corresponds to a test frequency at which the hearing threshold is determined. In combination with the Y-axis (hearing threshold in dB HL), this results in the individual hearing curve. The display enables quick recognition of frequency-specific hearing loss patterns such as high-frequency or low-frequency losses.

X-linked inheritance describes genetic diseases in which the responsible gene is located on the X chromosome and the frequency and severity varies depending on gender. Men (XY) are affected more frequently and more severely as they only have one X chromosome, while women (XX) are usually carriers and show mild or no symptoms. Known X-linked hearing disorders include certain forms of otosclerosis and rare syndromes with hearing loss. Molecular genetic diagnosis uses blood or saliva samples to identify mutations on the X chromosome. Genetic counseling is essential to assess family risks and initiate early interventions such as newborn screening.