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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