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Christian Meyer-Bisch

Publications and source records attributed to Christian Meyer-Bisch.

2 recordsLinked to original sources

[Noise-induced hearing loss: news in the regulation].

Noise-induced hearing losses (NIHL) are among the most often encountered occupational diseases in many industrial countries. This is true in terms of the number of exposed workers and in the amount of health insurance or State health care compensations. These handicaps are not reversible. In order to understand why this is, we will explain how high levels of noise pressure can affect the ear, by describing the three parts of the ear, including some details about the inner ear and its sensitive cells. Several epidemiological surveys indicate that an average of 6.8 %, French employees are exposed to dangerous levels of noise with vast differences according to their sector of activity. The most exposed are found in the wood and paper industries (37.4 %), in large plants and amongst intermittent workers. Males are five times more exposed than females, but they are much more numerous in these industries. About 5 million French people suffer from hearing disorders; 2 million of them are under 55 years of age. The Labour Ministry controls the occupational medicine services where exposed workers are subjected to a special check-up, which includes an audiometric examination at least every two years. But for the others, it is useful to know the danger signs of hearing disorders, like hearing fatigue (TTS), tinnitus or difficulties in understanding with background noise. Aging also affects hearing capabilities: this is called presbyacusis, which can be a confusing factor in the assessment of NIHL in older workers. In order to improve the protection of all workers in the EC, a recent European Directive will decrease the maximum level of tolerated noise (from the current 90 dBA) to 87 dBA before March 2006. In addition, the level at which a preventive programme has to be developed (hearing conservation programme) will start at 80 dBA instead of the current 85. The French compensation system for workers suffering from NIHL has also recently been modified. Such a modification will increase the number of compensations (probably by 4 times). The annual cost of the aforementioned compensations was 100 million in 2003.

Female↗

[Measuring noise].

High levels of noise encountered both in leisure activities and at workplaces can be somewhat annoying, but they can also cause hearing damage. In order to lessen these risks, some physical characteristics of the sound phenomenon need to be understood. The level of a sound is given in dB, a logarithmic unit in which simple addition is not available : 100 dB + 100 dB = 103 dB. The highest level of noise which can be tolerated by the human ear is considered to be 120 dB. Another component of sound characteristics is the frequency, which describes the height of a sound. The frequency is given in Hz, the human hearing field is comprised in the range of 20 to 20,000 Hz. Regarding the sensitivity of the ear, depending on the frequency, acusticians use a weighed dB, called dB(A), which takes into account a lower risk to hearing below 500 Hz and above 6 kHz. They also integrate the energy measured during a period of time to take the fluctuation of usual noise levels into account. So that currently, the levels of noise are often given in LAeq (equivalent to the level of continuous noise given in dBA). For moderate levels of noise, another weighted filter is used in sound level meters : the C curve, because low frequencies, although they are less dangerous for the ear, are more disturbing. In every day life, we sometimes have noise levels reaching 100 dB, and even 120 dB (fire alarms). Amplified music can reach 110 dBA, but a French regulation limits the output of PCPs (Walkmans) to 100 dB and the levels in concerts and discotheques to 105 dBA. At the workplace, the maximum level of noise allowed by French Law is 90 dBA for an 8 hour exposure, and 140 dB for peaks. In order to improve the protection of all workers in the EC, a recent European Directive will decrease the maximum level to 87 dBA before March 2006.

Hearing Loss, Noise-Induced↗