Real world attenuation of foam earplugs- smith

RAAF Institute of Aviation Medicine

Real-world attenuation of foam earplugs.

Dr Adrian Smith

RAAF Institute of Aviation Medicine

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

RAAF Institute of Aviation Medicine

RAAF Institute of Aviation Medicine

RAAF Institute of Aviation Medicine

Measured noise Factory attenuation data Calculated at-ear noise

exposure

… assuming that the wearer gets full benefit of earplugs.

• 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.

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.

This is how deep to insert earplugs!

Aim

Document real-world attenuation of foam earplugs.

Determine whether training improves attenuation.

Method43 aircrew, attending AVMED for training

Asked to insert earplugs as normal.– Blinded to purpose of the study– Not coached or corrected– Technique recorded

Attenuation measuredOne-on-one training, plus 10-sec video clipsAttenuation re measured

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%

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 protectionof an ‘informed user’

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

What about those with “formal training”?

*

After training…

Importance of technique

** *

* p<0.001

*

*

Does the training benefit everyone?

One size fits all....

One size fits most....

Small

Large

Improvement P-value‘Formal instruction’ already 10.1 dB

0.81Self-taught 9.4 dBPilot 8.4 dB

0.41Non-pilot aircrew 10.5 dBNewly-qualified (<100 h) 11.1 dB

0.15Experienced (>1500 h) 7.3 dBConfident in technique 9.4 dB

0 96

Who benefits from training?Attenuation P-value

Before training 15 dB<0.001

After training 26 dB

10 dB improvement … so what?

Every 3 dB=

double sound pressure level

Sound pressure level↓

Noise exposure↓

Risk of NIHL3 6 9 12 15

dB f tt ti

Conclusions

Foam earplugs in the hands of untrained users are significantly less effective than factory specifications.

ADF pers likely over-exposed to noise.

Brief training intervention– Insertion technique, improved

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?

Thank you

Dr Adrian Smith

Specialist Aviation Medical Officer (Army)RAAF Institute of Aviation Medicine

adrian.smith14@defence.gov.auTel: 08 7383 3169

Foam earplugs:

more interestingthan you think!

Thank you

Dr Adrian Smith

Specialist Aviation Medical Officer (Army)RAAF Institute of Aviation Medicine

adrian.smith14@defence.gov.auTel: 08 7383 3169