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Methods of protection from exposure to noise




Noise according to ДСН 3.3.6.037-99 should take noise-safe development of technology, the use of means and methods of collective protection [4], personal protection [6], as well as construction and acoustic methods.

Basic methods of reducing industrial noise, attenuation or elimination of the causes of noise at the source of its origin; Noise reduction in the ways of its distribution; use of personal protective equipment.

The weakening of the noise at the source of its origin are the most efficient means to combat noise.

Reducing noise in the way of its distribution is achieved complex construction and acoustic measures. These include rational planning decisions (first removing noise sources in an appropriate distance from the objects to be protected, sound insulation, sound absorption and noise reflection).

The noise propagating in air (air sound), the most radical can be lowered towards arranging its distribution soundproofing barriers in the form of walls, partitions, ceilings, special soundproofing casings, cabins, etc.

The sensitivity of human hearing decreases with decreasing frequency sound. For example, the human ear perceives pure tone (also known musical tone - a sinusoidal oscillation) frequency of 100 Hz, a sound pressure level of 44 dB, as that is equal to the volume pure tone frequency 1000 Hz sound pressure level of 29 dB. In Engineering International Electrotechnical Commission identified various corrective frequency characteristics A, B, C and D. As a standard frequency response adopted the so-called scale A which is closest to the frequency response of the hearing aid sensitivity perception person.

In the case of constant noise power 70 dB occurs disorder of the endocrine and nervous systems, 90 dB - disturbed hearing, 120 dB - there is unbearable physical pain.

 

Various sources noise intensity, dBA

Source of noise Noise level, dBA
Winter forest, quiet weather
Whispering
Rural locality
Library
Machinery bureau
Automobile interior
Jackhammer
Heavy tip truck
Pop-music orchestra
Lightning
Jet aircraft at 25 meters
Space rocket launch

Vehicle noise is the excess of natural noise caused by the engine, wheels, brakes and aerodynamic features of the vehicle. The total noise of automobile which contains of the noise that the engines, car body, accessories, rustling of rolling tires airflow. Noise occurs when the engine and the whole car can be divided into two groups - aerodynamic and mechanical. Aerodynamic noise is the result of gas exchange in the engine during the intake process fresh charge and exhaust, as well as the interaction of fan blade with air. Mechanical noise causing combustion process and dynamic processes in the crank mechanism, Valve gear, lubrication system, cooling system, power supply and so on. Aerodynamic noise passes air, mechanical noise - the outer surface of the engine and vehicle units.



 


 


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