Audiometry

𝗢𝗿𝗶𝗴𝗶𝗻𝗮𝗹 𝗗𝗲𝘀𝗰𝗿𝗶𝗽𝘁𝗶𝗼𝗻: Audiometry is the measurement of the sensitivity and range of an individual's hearing. As many etiologies of imbalance, nystagmus, vertigo and/or dizziness can have an otologic origin the audiogram is an important piece of information in the evaluation of the dizzy patient. A basic audiogram (Fig. 1) tests an individual's threshold to hear pure tone signals presented over a wide range of frequencies, typically from 250Hz to 8Khz. The threshold for hearing is defined as the lowest sound level for which an individual can identify a pure tone signal 50% of the time. The sound level in audiograms is presented as decibels of hearing level (HL). Hearing level is calibrated by the American National Standards Institute (ANSI) to sound pressures based on the hearing ability of a healthy young adults tested in quiet conditions. Therefore, hearing a noise at 0 dbHL, means that is the softest sound that the average healthy young adult could detect 50% of the time. Levels of hearing loss are defined by the amount of decibels above 0 dbHL an individual's hearing thresholds are. An individual with a 40dB HL hearing loss has a hearing threshold 40dB higher than the softest noise a healthy young adult could hear in a quiet environment. Normal hearing is considered anything between -10-20dB HL, mild loss is 25-40db HL, moderate 40-50db HL, moderately severe 55-70 db HL, severe 70-90dbHL and profound is >90 db HL. Audiograms test both an individual's ability to hear noise transmitted through air, via the ear canal, as well as their ability to hear noise transmitted through bone. Understanding the differences between a conductive hearing loss (a decrease in hearing for air conducted sounds) and a sensorineural hearing loss (a decrease in both air and bone conducted sounds) is important to distinguish the etiology of hearing loss and its possible correlation with any balance symptoms. 𝗡𝗲𝘂𝗿𝗼-𝗼𝗽𝗵𝘁𝗵𝗮𝗹𝗺𝗼𝗹𝗼𝗴𝘆 𝗮𝗻𝗱 𝗡𝗲𝘂𝗿𝗼-𝗼𝘁𝗼𝗹𝗼𝗴𝘆 𝗧𝗲𝘅𝘁𝗯𝗼𝗼𝗸 𝗟𝗲𝗴𝗲𝗻𝗱: An introduction to audiometry