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36
Spécial “ Noise at work 2007 ”
Acoustique
&
Techniques n° 49
Practical noise attenuation of hearing protectors according to noise directive 2003/10/EC
devices. This means that the daily noise exposure is about
87 dB. This means that no additional noise exposure
should occur during that day. If there is a delay with engine
testing, the only way to continue is to substitute a worker,
which can increase a risk of operational safety of that
machine. Therefore, an extremely sophisticated method of
evaluation is needed for this work. In the abovementioned
cases in Table 1 there is also an urgent need to develop
new technical noise control methods.
When hearing protection evaluation was conducted for the
implementation of the noise directive limit value (87 dB),
our tests showed that the exposing noise value could be
more than 100 dB for a general wide-frequency noise
spectrum. When the noise is low-frequency or the user
has not inserted the ear plug properly, the noise level of
exposure can be even less — down to as low as 95 dB,
as pointed out by Finnish labour protection authorities.
Since measurements and evaluations are associated with
significant uncertainty, emphasis should be placed on the
technical means of reducing noise exposure. However, for
critical conditions workplaces should seek expert help.
These are very simple guidelines that workplaces require
when conducting their evaluation. Standard EN 458 gives
good guidance to evaluate the noise attenuation of hearing
protectors. It also considers frequency and impulse
responses. However, it relies strongly on laboratory
attenuation values that are not achieved, as described in
previous discussion. Therefore, a safety coefficient should
be used. In addition, the validity of the methods is low if
the workers cannot choose between several protectors,
because of the variation in the morphology of the face.
Still, the parallel use of other protection devices may
reduce attenuation. Therefore practical factors and safety
culture have an influence on real noise attenuation, which
must also be evaluated.
Bibliography
1. Berger E. (1986) Methods of measuring the attenuation of hearing protection
devices.
J. Acoust. Soc. Am. 79 (6) : 1655-1687
2. Berger E. (1988) Can real-world hearing protector attenuation be estimated
using laboratory data. Sound Vibration, 22 (12) : 26-31
3. Casali JG and Berger EH. (1996) Technology advancements in hearing
protection circa
1995: active noise reduction frequency/amplitude-sensitivity, and uniform
attenuation. AIHA J. 57 (2) : 175-185
4. Directive 2003/10/EC (2003) On the Minimum Health and Safety
Requirements Regarding the Exposure of Workers to the Risks Arising from
Physical Agents (Noise). Official Journal of European Union, L42/38-44
5. EN 352. Hearing protectors — Safety requirements and testing — Part 1 :
Ear-muffs, Part 2 : Ear-plugs, etc. CEN 1992. Several standards.
6. European standard EN 458. Hearing protectors — Recommendations for
selection, use care and maintenance — Guidance document. CEN September
1993. 34 p.
7. Pekkarinen J (1989) Exposure to Impulse Noise, Hearing Protection and
Combined Risk Factors in the Development of Sensory Neural Hearing Loss.
Doctoral dissertation. Publications of the University of Kuopio 4/1989. University
of Kuopio, Finland. 87 p. + app. 59 p
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plug fit and attenuation — An experimental study. Acustica — acta acustica 86 :
481-484
9. Pääkkönen, R., Lehtomäki, K. & Savolainen, S : Noise attenuation of hearing
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10. Pääkkönen, R., Lehtomäki, K., Savolainen, S., Myllyniemi, J & Hämäläinen,
E. : Noise attenuation of hearing protectors in the human ear-a method
description. Acta acustica
86 (2000c), 477-480.
11. Pääkkönen, R., Savolainen, S., Myllyniemi, J., Hämäläinen, E. & Lehtomäki,
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