1. The hazards of environmental noise pollution
The impact and harm of noise on human body can be generally divided into two aspects: labor protection and environmental protection. The former refers to harm to human health and leads to various diseases. The latter refers to interference with the quiet environment and affects people's normal work and life. The main hazards of noise to human health are: damage to hearing and noise-induced deafness; lead to cerebral cortex excitement and balance disorders, damage to cerebrovascular function, resulting in neurasthenia; damage to the cardiovascular system, causing digestive system disorders, affecting endocrine; interfere with people Life, rest, language conversation and daily work and study, distract attention and reduce work efficiency. Most residents can easily ignore the harm caused by elevator noise, because the noise generated by elevators is generally low to medium frequency, and the human ear is not very sensitive to low frequency. However, through practical research, we found that in fact, low-frequency noise may also affect people's internal organs health.
2. Basic principles of noise control
The formation of noise pollution is mainly due to three factors, namely: sound source, transmission medium and receiver. Only when these three exist at the same time can it interfere with the listener. Starting from these three aspects, the purpose of noise control is achieved by reducing the sound source, limiting noise propagation, and blocking noise reception. In specific noise control technology, vibration isolation, sound absorption, sound isolation and attenuation can be used. Sound and other measures.
Sound absorption: When sound waves are incident on the surface of an object, part of the sound energy is absorbed by the object and converted into other forms of energy, called sound absorption. The sound absorption performance of the material is expressed by the absorption coefficient. The larger the sound absorption performance, the better the sound absorption performance of the material. The sound absorption performance of a material is related to the nature, structure, angle of incidence of the sound wave, and frequency of the sound wave. The sound absorption mechanism of porous sound-absorbing materials is: there are countless small interpenetrating holes inside the material. When sound waves are incident on the surface of these materials and then into these small pores, it is necessary to cause air movement in the pores. The air on the hole wall and the fiber surface is not easy to move due to friction and viscous movement resistance, so that the sound energy is converted into heat energy and consumed. Therefore, sound-absorbing materials with good performance should be porous, and the holes should penetrate each other, and the penetrating holes should communicate with the outside world so that sound waves can enter the interior of the material.
Sound insulation: The method used for sound insulation is to close the noise source and control the noise in a small space. This sound insulation structure is called the sound insulation cover. When the sound wave encounters the shield, due to the change in the characteristic impedance of the interface, part of the incident acoustic energy is reflected and partly absorbed, and part of the acoustic energy penetrates into the shield and continues to propagate. The sound insulation performance of the material can be expressed by the sound transmission coefficient. The smaller the sound transmission coefficient, the less sound energy is transmitted through, and the better the sound insulation performance of the material. The sound insulation performance of the material is related to the structure and properties of the sound insulator and the frequency of the incident sound waves.
Muffler: Muffler is to fix the porous sound-absorbing material on the inner wall of the air flow channel, or in a certain way in the pipeline, in order to weaken the aerodynamic noise, the noise reduction can generally reach 15-40 decibels.
3. Governance technical measures
There are three main aspects that need to be paid attention to to solve the elevator noise. First, the elevator design stage should consider the elevator installation location, installation method, and adopt active sound insulation and noise reduction measures, such as machine room sound insulation, etc.; second, the elevator production unit should be selected after strict The calculated vibration isolation equipment and facilities; the third is that elevator users should strengthen maintenance to ensure normal operation.
We know that elevator is a large-scale equipment. The high-speed operation and start of the motor when running and stopping, the suction and tension of the brake when parking, etc. determine the inevitability of noise and vibration. Therefore, the state has made relevant regulations on elevator noise standards. "According to the latest elevator noise standards formulated in 2003, the elevator noise value measured in the elevator machine room should be ≤80 dB."
More info: Suxun Elevator Co.,Ltd.
