1. Measurement and
assessment of exposure to
noise in a working
environment
Difficulties and responsibilities
ICA2007MADRID - F. KRAJCARZ Slide n°1

2. French regulations
Decree 2006-892 of 19 july 2006
- lower exposure action value : Lex8h = 80 dB(A) or
Lpc = 135 dB(C),
- upper exposure action value : Lex8h = 85 dB(A)
or Lpc = 137 dB(C),
and
- exposure limit value : Lex8h = 87 dB(A) or Lpc =
140 dB(C), including Hearing Protector abatement
ICA2007MADRID - F. KRAJCARZ Slide n°2

3. Measuring standard
NFS 31084 (October 2002)
- systematic measurements
or
- after the analysis of the work, and grouping in
Homogeneous Exposure Group (HEG) :
task-based measurements
or
job-based measurements
ICA2007MADRID - F. KRAJCARZ Slide n°3

4. Gamba Acoustique references
- Several thousands of measurements in 15 years
- Participation to working groups (AFNOR / NFS
31084, ISO 9612)
- Agreement of the French Ministry of Labour
- Software developing : DiagLexd® dedicated to
assessment of noise-at-work, including Hearing
Protectors
ICA2007MADRID - F. KRAJCARZ Slide n°4

5. Experience feedback
- Uncertainties “never” under ± 3 dB(A)
- Measurement effort given by NFS 31084 is really
a minimum (often has to be increased of 50% or
more)
- Some situations can not fit the standard
requirements (very long cycles or maintenance
workers)
- Confusion between “noise mapping » and
« dosimetry »
ICA2007MADRID - F. KRAJCARZ Slide n°5

6. Comparison to exposure limit value :
Lex8h = 87 dB(A)
ELV = Lex8h (or Lex40h) – attenuation of Hearing
Protectors
following the requirements of NF EN ISO 4869-2
ICA2007MADRID - F. KRAJCARZ Slide n°6

7. Actual and theoretical protection
of Hearing Protectors
Significant difference between theoretical and
actual protection * : up to 10 or more dB
and
non-wearing duration is very important
* References : Casali ; Pääkkönen ; ...
ICA2007MADRID - F. KRAJCARZ Slide n°7

8. Maximum attenuation based on
the non-wearing duration of HP
Duration of
wearing
Duration of non-wearing
Maximum
attenuation
4h00 50% 4h00 50% -3 dB
6h00 75% 2h00 25% -6 dB
90% 48mn 10% -10 dB
95% 24mn 5% -13 dB
7h12
7h36
7h55 99% 5mn 1% -20 dB
The time you wear your HP may be more
significant than the type of HP you wear !
ICA2007MADRID - F. KRAJCARZ Slide n°8

9. Experience feedback about HP wearing
(year 2006)
- wide-ranging measurement (approximately 1000
subjects) > 4 sites of the same industrialist
- noted, for each instrumented workers :
- type of HP (simple earplugs, moulded
earplugs, helmet or “no HP”)
- duration of wearing of the HP, declared
verbally and anonymously by the workers
ICA2007MADRID - F. KRAJCARZ Slide n°9

10. Type of HP worn on the 4 sites
No protector Ear plugs Moulded ear
plugs
Helmets
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Site 1
Site 2
Site 3
Site 4
ICA2007MADRID - F. KRAJCARZ Slide n°10
Percentage %

11. Declared durations of HP
"Always worn" "Worn less than 90% of the
time"
70
65
60
55
50
45
40
35
30
25
20
15
Site 1
Site 2
Site 3
Site 4
ICA2007MADRID - F. KRAJCARZ Slide n°11
Percentage %

12. Declared durations / Lex8h
Lex8h < 80
dBA
"Never worn"
"Always worn"
"Worn < 90% of the time"
80< Lex8h < 85 85< Lex8h < 97 Lex8h > 97
dBA
100
90
80
70
60
50
40
30
20
10
0
ICA2007MADRID - F. KRAJCARZ Slide n°12
Percentage %

13. Declared durations / Lex8h
"Never worn" "Always worn" "Worn < 90% of the
time"
100
90
80
70
60
50
40
30
20
10
0
Lex8h < 80 dBA
80< Lex8h < 85
85< Lex8h < 97
Lex8h > 97 dBA
ICA2007MADRID - F. KRAJCARZ Slide n°13
Percentage %

14. Questions ...
47 % of workers (of this study) exposed > 85
dB(A) never wear hearing protectors ?
24 % of workers (of this study) still exposed >
87 dB(A) in spite of hearing protectors ?
ICA2007MADRID - F. KRAJCARZ Slide n°14