The document summarizes a study conducted by the RAAF Institute of Aviation Medicine to measure the real-world effectiveness of foam earplugs when used by untrained users, compared to laboratory tests. 43 aircrew had their earplug insertion technique and noise attenuation measured before and after a brief insertion training. Results showed that before training, earplugs provided significantly less attenuation than factory specifications, but attenuation improved by an average of 10 dB after training. The study demonstrates the importance of proper insertion technique training to maximize hearing protection and reduce noise exposure risks for aircrew.

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