The X-axis in an audiogram represents the frequency of the test tone, typically from 125 Hz to 8 kHz (up to 16 kHz in high-frequency audiometry). It is logarithmically scaled to clearly show the broad range of human hearing and to visualize tonotopy. 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 allows quick identification of frequency-specific hearing loss patterns such as high-frequency or low-frequency losses.

X-linked inheritance describes genetic disorders in which the responsible gene is located on the X chromosome and the frequency and severity vary depending on gender. Men (XY) are more frequently and severely affected because 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 diagnostics use blood or saliva samples to identify mutations on the X chromosome. Genetic counseling is essential to assess family risks and initiate early measures such as newborn screening.