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Spécial “ Noise at work 2007 ”
15
Acoustique
&
Techniques n° 49
Participative strategy of risk management applied to the problems of noise at work
First, an attempt is made to assess the personal noise
exposure level of the workers. A trained occupational health
specialist is invited to determine the appropriate time and
duration of the measurements, to control the validity of the
measuring technique, to perform the measurements and
estimate the exposure duration at each measured level, if
different conditions exist.
The measurements are restricted to A-weighted noise levels.
They should preferably be performed using a calibrated
exposimeter recording, for instance, the equivalent noise level
every 15 seconds. From the equivalent noise levels LAeq and
exposure durations, it is recommended to compute for the
different noise sources the partial personal noise exposure
levels LPE,i., that is, the personal noise exposure level if all
other noise exposures were insignificant. These partial LPE,I
levels make it possible to determine what work sequences,
what situations or what noise sources are the most responsible
for the risk of discomfort or hearing impairment.
The total personal noise exposure level (LPE) is estimated as
usual by the addition of the partial exposure levels.
The interpretation scale is more quantitative than in stage 2,
Observation
, from light discomfort, to a probability of 75%
to suffer from a NIHL at the age of 55 years in case of an
exposure to these conditions during 35 years.
Discomfort is linked not to the personal noise exposure level
but rather to the equivalent level in the short term.
The risk of hearing impairment on the contrary is in relation
to the LPE.
The users are then invited to go through the list of possible
solutions and identify what could be done to reduce the risk
of discomfort or hearing impairment.
As in stage 2,
Observation
, they are invited to estimate what
the situation might be if these solutions were implemented
and to estimate the residual risk. If this risk is unacceptable,
additional efforts and information are required: a stage 4,
Expertise
, must be undertaken with the further assistance
of an expert.
They will finally draw up the inventory of the technical measures,
define deadlines and allocate responsibilities for actions.
At this stage, more than in stage 2,
Observation
, the
users have adequate training and enough information to
determine :
• Whether personal protection must be worn;
• What protection should be carried on, by whom, when and
for how long;
• Who should participate in the audiometric programme and
when.
The document draws the attention on some main aspects
of the personal protection. These recommendations are
based on the fact that the best protective device is the one
that is worn during the longest period of time [16, 17].
Emphasis is therefore placed on convenience to use, comfort,
aesthetics, rather than on the intrinsic attenuation capacity.
Stage 4, Expertise
At this stage, the overall situation should be known and
attention will concentrate on very specific items such as the
reverberation of the hall, the damping of a vibrating structure,
the silencing of a resonating structure… This will involve
specific, highly sophisticated measurements and the experts
should know what to do in a given case.
The only aspect to stress is the absolute necessity to assist
this expert. Much too often, the problem is transferred to the
expert and he is expected to solve it by himself.
As underlined in table 1, this strategy is based on the
complementarity between the
Expertise
of the workers and
the
Expertise
of the specialists.
Validation
The strategy was validated in ten SME of various industrial
sectors. It proved to be understood, accepted and used
and showed its effectiveness to improve the working
conditions, to train the operators, to support the use of
personal protective equipments and the adoption of adequate
procedures of work.
Conclusion
The strategy has three major characteristics:
First, it is realistic: noise regulations exist for decades. Still,
many workers are exposed to harmful noise. Motivation is
limited in industry, since time, budget, technical resources
and competence in acoustics are limited. The assessment
and prevention procedures is optimised, starting from what
industry is willing and able to do.
Second, it is participative: the workers and their management
play the essential role in the dynamics of the improvement
of the working conditions. Occupational health specialists
and experts are there to assist, in order to identify the most
adequate technical and organisational control measures.
Third, it is structured in 4 stages that require complementary
knowledge and competencies:
At the two first stages,
Screening
and
Observation
:
knowledge of the industrial process, the machines and the
working procedures.
At the
Analysis
stage: assistance of specialists with education
and training about the general methodological aspects, the
common measuring and evaluation techniques, the main
technical solutions;
At the
Expertise
stage: when it is absolutely necessary,
assistance of highly trained experts who will bring their specific
knowledge for the identification of particular solutions.
The strategy is not designed for experts but for the industry,
calling in experts when needed. This itself might be utopian
in many industrial settings, at least at the present time.
Specialists can still use the strategy directly to initiate the
procedure, demonstrate its simplicity and usability. Contrary
to what is done too often, the experts are not called in to be
responsible for finding the solutions, but the whole process of
searching for solutions is carried out in full partnership.
The strategy does not therefore exclude the participation of a
specialist from the start. Simply, it does not rely on this.