Pure tone audiometry

Pure tone audiometry
Medical diagnostics
Diagram of the human ear
ICD-9-CM	95.41
MeSH	D001301
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Pure tone audiometry (PTA) is the key hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss. Thus, providing the basis for diagnosis and management. PTA is a subjective, behavioural measurement of hearing threshold, as it relies on patient response to pure tone stimuli. Therefore, PTA is used on adults and children old enough to cooperate with the test procedure. As with most clinical tests, calibration of the test environment, the equipment and the stimuli to ISO standards is needed before testing proceeds. PTA only measures audibility thresholds, rather than other aspects of hearing such as sound localization and speech recognition. However, there are benefits of using PTA over other forms of hearing test, such as click auditory brainstem response (ABR). PTA provides ear specific thresholds, and uses frequency specific pure tones to give place specific responses, so that the configuration of a hearing loss can be identified. As PTA uses both air and bone conduction audiometry, the type of loss can also be identified via the air-bone gap. Although PTA has many clinical benefits, it is not perfect at identifying all losses, such as ‘dead regions’ of the cochlea and neuropathies such as auditory processing disorder (APD). This raises the question of whether or not audiograms accurately predict someone’s perceived degree of disability.

There are both international and British standards regarding the PTA test protocol. The British Society of Audiology (BSA) is responsible for publishing the recommended procedure for PTA, as well as many other audiological procedures. The British recommended procedure is based on international standards. Although there are some differences, the BSA-recommended procedures are in accordance with BS EN ISO 8253-1, which is the international standard for PTA established by the International Organization for Standardization. The BSA-recommended procedures provide a "best practice" test protocol for professionals to follow, increasing validity and allowing standardisation of results across Britain. The British Society of Audiology. Recommended Procedure: Pure Tone air and bone conduction threshold audiometry with and without masking and determination of uncomfortable loudness levels.