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Spécial “ Noise at work 2007 ”
33
Acoustique
&
Techniques n° 49
Atelier : Protecteurs individuels : quelle est leur
atténuation réelle ?
Practical noise attenuation of hearing
protectors according to noise directive
2003/10/EC
he implementation of the new noise directive
2003/10/EC sets a limit value that must not be exceeded
when hearing protective devices (HPD) are used. The
simplest way to compare the exposure limit values is to
measure the noise exposure outside the hearing protector
and then evaluate the exposure inside it by using one of the
methods given in EN458. Since the attenuations provided
by the manufacturers are based on laboratory results,
they tend to overestimate the practical attenuation. In
addition, the use of several protectors may decrease the
attenuation of HPDs. Thus there are situations in which this
exposure inside the HPD must be measured, for example,
in a military environment, the wood-working industry or the
metal industry.
According to the noise directive, when noise exposure
exceeds 80 dB, hearing protection devices (HPD) can
be used and employers must provide HPDs for workers
upon request. When noise exposure of 85 dB is exceeded,
workers must use HPDs and the employer must make every
effort to ensure the wearing of hearing protectors. The
limit value is 87 dB expressed as a daily/weekly exposure.
Depending on the efficiency of hearing protectors, this
exposure limit is exceeded with ambient noise exposure
of 95-125 dB. In Finland the labour protection authorities
require expert evaluation of hearing protectors when
noise exposure of 95 dB is exceeded. Double protection
cannot normally be used because no attenuation data is
available for this solution. If double protection is used,
daily exposure can be as high as 130 dB, but beyond this
limit the possible solutions are the shortening of exposure
time and/or the use of technical noise control solutions.
In laboratory conditions the HPDs attenuate noise 20-
40 dB when measured as a SNR-index. However, there
are many indications that practical noise reduction in
working conditions is significantly less, such as 0-30 dB
(Berger 1986, 1988, Casali & Berger 1996, Pääkkönen
2000a-d). In addition, working, eating, speaking, and other
facial movements reduce the noise attenuation of hearing
protectors (Pääkkönen 2000a and 2000d). In a Finnish
study, average noise attenuation was 17 dB in industrial
Rauno Pääkkönen
Finnish Institute of Occupational Health
P.O. Box 486
FIN-33101 Tampere
Finland
E-mail : rauno.paakkonen@ttl.fi
Summary
In our measurement of standard ear muffs and plugs a noise attenuation of
10-24 dB was achieved. In practical circumstances the noise attenuation
of hearing protection is usually less than claimed in laboratory tests. Many
factors contribute to this, such as individual differences (morphology, beard,
hair, etc.) and skill in applying the protector. Secondly, simultaneous use of
other protective devices such as eyeglasses, respiratory devices or helmets
may reduce the attenuation of hearing protection. At the workplace level, very
simple evaluation models are required or attenuation evaluation requirements at
workplaces are ignored.
Résumé
Nos mesures de performance des protections auditives classiques (casques et
bouchons d’oreille) ont montré que ces dernières offraient une atténuation du
bruit allant de 10 à 24 dB. En pratique, l’atténuation produite par les protections
auditives est généralement inférieure à celle revendiquée par les tests en
laboratoires. De nombreux facteurs contribuent à cette différence, comme les
caractéristiques individuelles (morphologie, barbe, cheveux, etc.), et l’habileté
à mettre en place les protections auditives. En outre, l’utilisation simultanée
d’autres équipements de protection comme des lunettes, des masques
respiratoires, ou des casques, peut diminuer l’efficacité des protections
auditives. Il est nécessaire de recourir à des modèles d’évaluation très simples
sur les lieux de travail car les normes d’évaluation concernant l’atténuation du
bruit au travail sont ignorées lorsqu’elles sont trop complexes.
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