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Noise = invisible cause:2018-12-06

Noise = invisible cause

 

Normal people can hear voices with frequencies ranging from 20 to 20,000 hertz and low frequencies below 300 hertz. Medical experts have found that low-frequency noise not only causes functional damage to human body, but also may cause organic damage and mental damage. Yang Yun, Director of Special Inspection Department of Fujian Geriatric Hospital, said that low-frequency noise can directly reach the human ear bone, making people sympathetic nervous tension, tachycardia, elevated blood pressure and endocrine disorders. If people are disturbed by low-frequency noise for a long time, it is easy to cause neurosis such as neurasthenia, insomnia, headache, impaired memory and decreased comprehensive judgment ability. Foreign studies have also found that low-frequency noise can penetrate the abdominal and uterine walls of human body, affect fetal organ development, and even cause fetal malformation.


The environmental acoustics expert at the Guangdong Environmental Monitoring Center said, "The same is the sound of 70 decibels, the frequency of 100 Hz and 1000 Hz, the sound of the human ear is different. The natural frequency of the human body is basically in the low frequency and ultra low frequency range. It is easy to resonate with low-frequency sounds, so people will be troubled and feel uncomfortable. In addition, when low-frequency sounds propagate in the air, the air molecules vibrate less, the friction is slower, and the energy consumption is less, so the propagation is farther and the permeability is strong. Can easily cross obstacles such as walls and glass windows."


The senior engineer of the Guangzhou Environmental Monitoring Center said that besides the low-frequency noise sources such as elevators, transformers, frequency conversion air conditioners and bass horns, the low-frequency noise generated by engines in urban road traffic, especially in large passenger and freight cars and buses, is increasingly threatening people's health in the process of starting and accelerating. 。 Modern science and technology has developed many sound insulation materials with good effect, which can effectively alleviate high-frequency traffic noise. However, due to the strong penetration of low-frequency noise, closing doors and windows often fails to work. For example, when a bus stops and restarts, the noise spectrum generated by the bus stops and restarts is about 2-4 metres in half wavelength of sound wave at low frequency of 63 hertz, which is very close to the size of the interior of a residential building on the street. When the strong low frequency noise penetrates the glass into the residential room on the street, it often produces resonance phenomenon, which is extremely harmful to human health. 


Seeking the Solution to Low Frequency Noise Pollution from Many Aspects

 

Facing more and more serious low-frequency noise pollution problem, local governments, especially environmental protection departments are actively cracking it.  The director of the Xiamen Municipal Environmental Protection Bureau told the reporter that in response to the strong "subwoofer" problem of the citizens, Xiamen City is prepared to adopt the method of "disclosure and combination, and sparseness." The aspect of “sparse” is mainly in urban planning and construction of the entertainment industry and the catering industry. The “blocking” aspect is drafting and compiling management methods, and transforming the previous notification commitment system into an administrative approval system, from the source to entertainment. Enterprises conduct normative control.


"In addition to reasonable planning, the use of high technology and new materials may be a breakthrough in cracking low-frequency noise pollution." According to environmental acoustic experts from the Guangdong Environmental Monitoring Center, Guangdong's relevant acoustic experts and polymer materials experts have jointly developed a successful one. Sound insulation material - Mass Loaded Vinyl, outstanding performance in controlling low frequency noise. The appraisal results of the Guangdong Provincial Economic and Trade Commission and the Science and Technology Department show that Mass Loaded Vinyl has reached the current international advanced level in terms of use and performance.


According to the engineer of Guangzhou Environmental Monitoring Center Station, low-frequency noise caused by low decibel number has also attracted the attention of the relevant state departments, which are actively formulating a new standard for low-frequency noise pollution. It was revealed that the "Standards and Measurements of Noise Control in Social Life" has been approved by experts, but there are still some aspects that are being further studied and improved. Once it is introduced, the problem of low-frequency noise pollution can not be relied on will soon be changed.


Before the standard is issued, the government's functional departments can take advantage of some existing laws and regulations including the “Regulations on the Administration of Entertainment Places”, “Code for Design of Sound insulation for Civil Buildings” and “Key Points for Design of Healthy Residential Buildings” Deal with the pollution problem of low frequency noise and actively protect the health and interests of the people.