Noise-Induced Hearing Loss - American Academy of Audiology

Assessing Hearing Protectors in the
Clinic- How to Perform CPT 92596
NRR (dB)
Real-Ear Attenuation (dB)
Using the NRR
Not Really Right
dBA P =dBA w – ½ (NRR – 7)
workplace noise
protected employee exposure
• 50% derating: a safety margin to account for the field vs.
lab difference in the labeled NRR.
• 7-dB correction: another safety margin to account for the
spectral uncertainty (i.e., the difference between the C
and A weighted levels).
35
30
25
20
15
10
5
0
-10
0
10
20
30
40
Predicted vs. Field Values
V-51R
EP-100
Field
Soft
Custom
Method B
SoundBan
Com-Fit
UltraFit
Mark IV
H7P3E
Classic
H9A
UF-1
Classic+UF-1
Attenuation Data
Tom Thunder, AuD, INCE ( tthunder@comcast.net)
Label Test
50
.125 .250 .500 1.0 2.0 4.0 8.0
Frequency (kHz)
0
15 Std. Dev.
ANSI S12.6 -1997 (R2002)
REAT
(Real-Ear at Threshold)
ANSI S12.6 – 1997
(R2002)
Sound-field thresholds
measured without HPD
Sound-field thresholds
measured with HPD
The difference is the
attenuation of the HPD
(insertion loss)
American Academy of
Audiology (April 2009)
Method A:
- Fit by tester
- 10 experienced subjects
- 3 trials (30 runs)
Method B:
- Fit by subject
- 20 naïve subjects
- 2 trials (40 runs)
Laboratory Testing of HPDs
Reverberant Room
1/3
1/3-Octaveband Noise Signal
Best Practice Bulletin:
Hearing Protection-Emerging Trends: Individual Fit Testing
Any population-based statistical estimate of hearing
protector performance is a poor estimate of individual
performance.
If the purpose of HPD evaluation is to determine how well
specific HPDs work on specific people, then they must be
tested on individual people (similar to the quantitative fit
testing of respirators).
http://www.hearingconservation.org/docs/AllianceRecommendationForFitTesting_Final.pdf