Variation in tone presentation by Pure Tone Audiometers: the potential for error in screening audiometry

Regular paper

Christopher Barlow

Southampton Solent University

Tuesday 2 june, 2015, 09:20 - 09:40

0.4 Brussels (189)

Manual pure tone audiometry has been in consistent use for a long period of time, and is considered to be the ‘gold standard’ for the assessment of hearing thresholds. Increasing legislative requirements, and a significant global cost impact of noise induced hearing loss, means that a significant amount of reliance is placed on this tool for diagnosis. There are a number of questions regarding the degree of accuracy of pure tone audiometry when undertaken in field conditions, particularly relating to the difference in conditions between laboratory calibration and clinical or industrial screening use. This study assessed the test-retest variability of a number of commercially available screening audiometers, all with recent calibration, using both laboratory and clinical testing. Laboratory tests used a Bruël and Kjaer Head and Torso simulator to measure the output sound pressure level of 4 different commercial audiometers in a simulated clinical environment. Tests used 3 presentation levels and test frequencies of 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz and 6 kHz. Clinical tests used pure-tone conduction assessment in accordance with ISO 8253- 1:2010 to assess the hearing thresholds of 12 volunteers, including subjects with both normal and impaired hearing, with a number of tests repeated over a 3 week period. The results of both lab and patient studies showed a high level of test-retest variability, with maximum between test variation of 21 decibels at some frequencies in the lab tests, and 20 dB in the clinical tests. Significant variation occurred at all frequencies, with a particularly high level of variation at 6kHz for all meters. A further finding was that the use of attenuating cups with the audiometer headphones significantly increased the degree of variation. Levels of variation measured in this study suggests a high potential for diagnostic error when using screening pure tone audiometry.

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