Noise is an acoustic phenomenon producing an auditory sensation uncomfortable and unpleasant. Noise is also often perceived as aggression.
Despite considerable efforts to prevent the noise nuisance is frequently encountered in many companies in all sectors. Over 5 million people complain of noise and their workplace and more than 3 million are exposed to noise levels of 85 decibels or dB (A), which is currently the regulatory threshold.
A simple way of assessing subjective sound level: If one has difficulty speaking to a person within one meter and must raise their voices, the level of 85 dB (A) is reached.
Third leading cause of occupational disease
The hearing impairment caused by noise lesion is the third leading cause of occupational disease more common after the peri-articular disorders or MSDs (musculoskeletal disorders) and disorders resulting from the inhalation of asbestos dust. About 600 occupational deafness are recognized annually with an average unit cost of 100 000.
The frequencies that can be perceived by the human ear range from 20 Hz (sounds serious) to 20 000 Hz (high tones) with a maximum sensitivity to sounds between 1 000 and 6 000 Hz The human voice is, in speech frequencies between 500 and 2 000 Hz.
The intensity is expressed in decibels or dB (A), which is a logarithmic unit of measurement. Any increase of 3 dB represents a doubling of loudness. For an additional 10 dB, the intensity is multiplied by 10. The weighting reflects the sensitivity of the human ear, which is more important for frequencies between 1 000 and 6 000 Hz.
The noise dose received is equivalent to exposure to 85 dB (A) for 8 hours, 88 dB (A) for 4 hours, 94 dB (A) for 1 hour, 115 dB (A) for 1 minute …
The threshold of pain is 120 dB (A), which corresponds to the level of noise generated by a jackhammer. Beyond 120 dB (A), severe injuries are feared with torn eardrums. A gun causes the same noise level as a testbed aircraft engine: 130 dB (A) …
At equal intensity, the sharp sounds and pulse are more dangerous than the serious and continuous noise.
The negative effects of noise
Fatigue hearing is the first stage of the effects of noise on the ears. It came hours after exposure to loud noise with a temporary decrease in hearing, which often manifests as a feeling of blocked ears, sometimes with tinnitus, characterized by ringing or buzzing in the ears. This damage is reversible with recovery usually complete hearing loss and tinnitus usually complete within hours or days.
The occupational deafness is characterized by a deficit-centered 4 000 Hz, which will gradually widen and expand to other frequencies. Initially, the ear hole or scotoma causes no discomfort because it is beyond speech frequencies (500 to 2 000 Hz).
Only later, when the achievement has increased and it became irreversible as the person becomes aware of difficulties with its partners to understand and communicate, especially when several people speak. Tinnitus can significantly increase the social and professional embarrassment exists.
Early detection of occupational deafness based on the achievement of regular audiograms. To be reliable and interpretable, the tests must necessarily be conducted in a soundproof booth. They also verify the effectiveness of collective and individual protection.
Some people are more vulnerable than others to noise and may have more severe hearing damage for the same noise exposure. This fragility may result from conditions related to infectious factors, toxic substances (including medication), traumatic or hereditary. The sensitivity to noise increases with age and becomes more pronounced at age 50.
The effects of noise are not limited to the ear but should apply to the entire human body, generating, among other things: stress, concentration difficulties, memory disturbance, mood disorders with aggressiveness, irritability, anxiety , sleep disorders …
The occurrence of accidents may be favored by these disturbances, which are superadded the masking noise that interferes with the perception of acoustic signals and safety of the floor.