Audiological Tests For NIHL
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Audiological tests are used to evaluate noise-induced hearing loss (NIHL). A case history is taken including noise exposure details. Pure tone average and high frequency audiometry from 8-20kHz are conducted to detect early NIHL. Tests show initial notch at 15kHz before losses below 8kHz. Periodic baseline and monitoring tests track threshold shifts over time to identify NIHL. Proper testing procedures and equipment calibration are needed to accurately diagnose NIHL.
Audiological Tests For NIHL
- 1. Audiological tests for NIHL Prepared by Vishnu Mohan
- 2. Audiological tests • Case history • Pure tone average • High frequency audiometry • Immittance • OAE • AEP • Special test
- 3. • Case history: – Type of noise – Duration of work hours per day – Duration of exposure – Previous exposure to noise – Environment at home – Loudness of noise – Any previous evaluation undergone – Family history of HL (presbycusis) – Any other susceptible factor – Use of any EPD’s
- 4. • Sign & symptoms: – Unilateral / bilateral – Tinnitus – Giddiness – Ear pain – Sensitive for sounds – Hearing loss – Speech intelligibility (specially in the presence of noise) – Any voice problem
- 5. • Pure tone average: – 8 KHz to 20KHz high frequency audiometry • To extend, confirm / reject clinical impression • For early detection, description differentiation of NIHL • Usually notch is seen at 15KHz, even before any loss seen <8KHz • This tells us about sub-clinical HL – Mid octave need to be tested – Testing to be done in sound treated room with calibrated audiometers – Experienced audiologist should test
- 6. – Early stages BC notch is seen usually at 4KHz, but at later stages it becomes flat – In gun shooters HL is seen more in left ear for right handers – Truck drivers – asymmetrical HL – Factory workers – symmetrical – Age correction factor has to be added to differentiate them
- 7. • Stephen et al(1981) – Threshold shifts between 8KHz – 20KHz – Prominent was between 13 – 20 KHz – This was for steady state noise – Maximum threshold shift was 20 dB to 35 dB
- 8. • Baseline and periodic monitoring tests: – Pre employment hearing tests: •All employers should undergo hearing testing •Bryan and Tempest (1980) – questionnaire need to be administered, about prior exposure before employment •Periodic follow up tests •Baseline audiogram / reference audiogram
- 9. • Monitoring audiometry: – Workers exposed to more than 85dB level, monitoring should be frequent – After strike, long leave, sick leave – audiometry should be done – If person claims for any compensation then aging effect and effect of ototoxicity should be taken care off – Counseling is very important • Use of EPD’s • Susceptible factors • Prevention of hearing loss
- 10. • Instrumentation: – Pure tone audiometry • Screening • Diagnostic • Speech – Manual or automatic – Manual-3 basic types • Wide range • Limited range • Narrow range – Should have facility varying intensity as well frequency
- 11. – Automatic: • Fixed frequency type is used • Each test frequency is usually presented sequentially in periods of 30 sec • Intensity level is controlled by the person who is being tested • Valid – test for 6 times at each test frequency, and take the average – (Melnick, 1987), manual is more advantages • as the tester has greater flexibility over testing procedures and test situations
- 12. • as the tester has greater flexibility over testing procedures and test situations • Reduces operator error • Unique to the situation • In large industrial situation it will permit testing fro several persons • Task is comparatively easy
- 13. sweeps Discrete/octave Frequency Case Examiner Intensity manipulation tracing Examiner Audiogram plot Examiner starts later controlled by itself Audiologist Stimulus presentation Automatic Manual
- 14. fixed Examiner Interval b/w stimulus Until threshold is not established Possible Rechecking Tester has more control Flexibility Single Double Channel Automatic Manual
- 15. • Checklist for audiometric evaluation: – Audiometers should be in good working position – Biologic calibration – Should be done under professional supervision – Employees receive immediate feedback of the audiogram
- 16. • Employees receive written feedback for the audiogram reviewer: – Hearing status compared to normal for age – Hearing change over time – Recommendation for better protection on and off work place – Medical examination or treatment if appropriate
- 17. • Quality control responsibility of technicians: – Maintaining test equipments – Environment – sound treated and away from distractions – Using constant instructions and testing methods – Maintaining complete records – Auditory history information – Checking hearing protection devices – Immediate feedback about hearing trends – Follow ups
- 18. THANK YOU