The primary speech frequencies fall between 5 Hz, although normal human hearing ranges from ~20 Hz to ~20,000 Hz. Variability is also expected when testing the same patient, due to differences in audiometry equipment, examiner, and patient factors for this reason, a change in hearing threshold of 5 dB is thought to be within the standard error of these measurements.Ī typical audiogram measures thresholds at frequencies within a range slightly broader than that of human speech, including 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz. Some level of variability across the population is expected, and hearing thresholds up to 25 dB are considered normal. Hearing Level is a scale based upon normative data for human hearing thresholds, devised such that 0 dB is the loudness at which most people can perceive a sound 50% of the time individuals that can hear better than average may, therefore, have hearing thresholds that are lower than 0 db. Pure tone thresholds are then plotted on an audiogram, displaying the quietest sound at a given frequency that a patient is able to discern, at least 50% of the time, measured in decibels Hearing Level (dB HL). Most commonly, tones at the frequency being tested are presented at decreasing intensity levels (in 5 or 10 dB steps) until becoming inaudible, and then are re-presented at increasing intensity until becoming audible again, a procedure known as the Hughson-Westlake method. Bone conduction thresholds are obtained via an oscillating transducer placed on the mastoid process. Pure-tone evaluations are performed in sound-treated rooms to eliminate ambient noise while obtaining hearing thresholds for both air-conducted and bone-conducted sound. Air conduction tones are presented through insert earphones or over-the-ear headphones. This review aims to explore the basic principles of audiometry and discuss the audiogram's interpretation, including examples of common pathologies that can be diagnosed via audiometry. ĭespite the ability of this powerful tool to guide clinical practice in managing patients with hearing loss, many healthcare providers have difficulty accurately interpreting an audiogram. In contrast, bone conduction measures transmission only from the inner ear to the CNS. Air conduction measures sound transmission from the outer ear, through the middle ear, and into the inner ear, where signals are sent to the central nervous system (CNS) for auditory processing. The configurations and patterns displayed on the audiogram help healthcare providers to understand the etiology and severity of a patient's hearing loss.Īudiograms are most useful for objectively identifying deficits in hearing by looking at how sound travels through the auditory system via air conduction or bone conduction. Audiometric testing utilizes various intensities of sound emitted over a range of frequencies to determine deficits in hearing, and results are plotted on a graph known as an audiogram. Subtle findings in young patients may warrant referral for audiometry, as children with even slight hearing impairment may suffer from speech and language delays.Īudiometric threshold data, also known as pure-tone testing, have been used clinically since the 1920s to categorize degree and type of hearing loss. Accurately diagnosing and managing hearing loss is important in patients of all ages, whether for safety and quality of life in adults or for developmental reasons in children. More than 16% of adult Americans experience some degree of hearing loss.
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