1. RAAF Institute of Aviation Medicine
Real-world attenuation
of foam earplugs.
Dr Adrian Smith
RAAF Institute of Aviation Medicine

2. RAAF Institute of Aviation Medicine
Noise-induced hearing loss
• Common occupational hazard
– Across industries
– Global
• Costs
– Australia, 24% of OH&S claims in last 10 yrs
– $$: compensation
– $$: lost productivity
– In Australia, $11 billion each year

3. RAAF Institute of Aviation Medicine

4. RAAF Institute of Aviation Medicine

5. RAAF Institute of Aviation Medicine

6. Measured noise Factory attenuation data Calculated
at-ear noise
exposure

7. • Roll earplug into a crease-free cylinder.
• Pull Back ear by reaching over head with free hand,
gently pull top of ear up and out.
• Insert earplug deep into ear canal.
• Hold until it fully expands.
• Visual check. The earplug should not be visible from the
front.
• Acoustic check. Earplugs should block enough noise
that covering your ears does not result in a significant
difference.

8. But…
Most earplug users do not receive formal
training to insert earplugs.
Start of training.
“These are earplugs.
t them in your ear when you are around loud noise”.
End of training.

9. This is how deep to insert
earplugs!

10. Aim
Document real-world attenuation of foam
earplugs.
Determine whether training improves
attenuation.

11. Method
43 aircrew, attending AVMED for training
Asked to insert earplugs as normal.
– Blinded to purpose of the study
– Not coached or corrected
– Technique recorded
Attenuation measured
One-on-one training, plus 10-sec video clips

12. Demographics
Aircrew
– Pilots, 24 (56%)
– Non-pilots, 19 (44%)
Experience
– Junior (1-100 hr), 53%
– Experienced (101-1500 hr), 28%
– Very experienced (>1500 hr), 19%

16. ANSI S12.6-1997
Earplugs inserted under direct vision
of a trained audiologist.
Earplugs inserted by naïve wearers,
following manufacturer’s instructions.
AS1270:2002
Optimum protection
Typical protection
of an ‘informed
user’

18. I S12.6-1997 Optimum performance,
inserted under direct control
of trained audiologist.
NRR 32 dB
270:2002 Typical performance
achievable by 80% of
‘informed users’.
SLC80 25 dB
s study. Performance of typical
population of users.
SLC801 18 dB

19. What about those with “formal
training”?

20. *

23. After training…

30. Importance of technique

31. ** *
* p<0.001

32. *

33. *

35. Does the training benefit everyone?

40. One size fits all....

41. One size fits most....
Small
Large

42. Improvement P-value
‘Formal instruction’ already 10.1 dB
0.81
Self-taught 9.4 dB
Pilot 8.4 dB
0.41
Non-pilot aircrew 10.5 dB
Newly-qualified (<100 h) 11.1 dB
0.15
Experienced (>1500 h) 7.3 dB
Confident in technique 9.4 dB
Who benefits from training?
Attenuation P-value
Before training 15 dB
<0.001
After training 26 dB

43. 10 dB improvement … so what?
Every 3 dB
=
double sound pressure level
Sound pressure level
↓
Noise exposure
↓
3 6 9 12 15

44. Conclusions
Foam earplugs in the hands of untrained
users are significantly less effective than
actory specifications.
ADF pers likely over-exposed to noise.
Brief training intervention
– Insertion technique, improved

45. Take-home messages
Earplugs are not intuitive to use.
Earplugs need formal, structured training
– Improved attenuation
– Reduction in occupational noise exposure
– Reduction in risk of noise-induced hearing loss
AVMED training module: Roll. Pull. Push. Hold. Check.
Target training or different earplugs?

46. Thank you
Dr Adrian Smith
Specialist Aviation Medical Officer (Army)
RAAF Institute of Aviation Medicine
adrian.smith14@defence.gov.au
Tel: 08 7383 3169

47. Foam earplugs:
more interesting
than you think!

48. Thank you
Dr Adrian Smith
Specialist Aviation Medical Officer (Army)
RAAF Institute of Aviation Medicine
adrian.smith14@defence.gov.au
Tel: 08 7383 3169