Technical measures should be taken to control noise from three aspects: sound source, sound transmission way and sound receiver (worker).
1. Controlling and eliminating noise sources is the fundamental measure. Through technological transformation, mute or bass equipment and technology should be used as much as possible to replace high-pitched equipment. Such as welding instead of riveting and hydraulic instead of forging; Strengthen machine maintenance or reduce unnecessary parts to eliminate noise caused by machine friction and collision; There is elastic material instead of metal to cushion the impact force at the machine collision, and rubber pad or copper-manganese alloy is added at the machine collision.
2. Reasonable factory planning and workshop design. That is, there should be a certain distance or protective belt between the workshop with strong noise and the non-noise workshop and office, and 90% of the windows of the noise workshop should be designed together with the non-noise workshop and office. The noise sources in the noise workshop should be concentrated as far as possible, and sound insulation measures should be taken. Sound-absorbing materials should be installed indoors, and sound-absorbing materials should be installed or painted on the walls to reduce the reflected sound in the workshop.
3. Take anti-noise measures for local noise sources, and isolate and seal the noise sources with noise elimination devices; Adopt vibration isolation device to prevent noise from spreading through solid; Epoxy resin is used to fill the gap between rotor slot and stator of motor to reduce electromagnetic noise.
4, control the spread and reflection of noise:
(1) Sound absorption: It acts on porous materials such as glass wool, slag wool, foam plastic and felt cotton wool. Decorate indoor walls or hang them in space, or make sound-absorbing screens;
(2) Noise elimination: it is suitable for reducing aerodynamic noise, such as intake and exhaust noise of various fans, air compressors and internal combustion engines. There are three kinds of mufflers designed according to the frequency spectrum characteristics of noise: resistive muffler, reactive muffler and impedance compound muffler.
(3) Sound insulation: the sound source is sealed with certain materials, structures and devices, such as sound insulation wall, sound insulation room, sound insulation cover, sound insulation door and window floor, etc.
(4) Damping and vibration isolation-Damping refers to coating foam on the air duct wall to reduce the vibration of the wall, and vibration isolation refers to installing damping devices and structures on the foundation, ground and wall where noise sources are installed. For example, a shock-proof rubber pad is installed on the base of the forging hammer, and sand is filled in the pipe of the column.
5. Personal protection: For technical or economic reasons, employees whose post noise exceeds the national health standards must wear earplugs, earmuffs or helmets to protect their hearing. Earplugs and earmuffs are made of soft plastic, soft rubber or fiber cotton. Wearing earplugs and earmuffs with appropriate models can reduce the sound insulation effect by 20-40dB (a).
6. Workers exposed to noise should be given regular hearing and general health checks. If it is found that the hearing in high frequency band continues to decline, which is beyond the normal fluctuation range (15-20 dB), it should be transferred from the noise operation post as soon as possible. New workers who have physical examination before employment and have hearing loss and obvious organic diseases of cardiovascular system and nervous system are not allowed to engage in noise operations.
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