Noise-related hearing loss is the most common occupational disease in Europe and North America, accounting for almost one-third of all work-related illnesses. These disorders can lead to long-lasting effects causing stress, fatigue or isolation that significantly increases the risk of work-related accidents caused by other factors. Hearing loss is irreversible and often detected late, so PPE covering this risk is classified as Category III.
Noise, as a vibratory phenomenon is characterized by:
The ear can be broken down into three distinct parts:
The human ear has a particular sensitivity to each frequency range. At moderate sound levels, it is less sensitive to low pitched sounds. To represent this particular sensitivity, the noise measurements and standards use a weighting of the measured sound levels called weighting A. The thus weighted decibels are denoted dB (A).
To choose the correct product for hearing protection.
The performance of the hearing protector (its attenuation level) must be adapted to the risk assessment of the workplace. It should bring the noise level to a level that is not harmful to health, while avoiding overprotection would cut the operator from his environment (warnings, communication...).
3 indicators, from the simplest to the most precise are made available to the user:
When hearing protection equipment can be worn in several ways (on the head and under the chin for example), it must be tested for each method of wearing.
When wearing a single hearing protector is not enough, it is possible to combine them. The attenuation resulting from the simultaneous wearing of earplugs with a B SNR and a noise-cancelling headset with an ST SNR is calculated by the following formula: 33 × log ((0.4 × B) + (0.1 × ST))