Noise protection. Occupational Safety and Health

OCCUPATIONAL SAFETY AND HEALTH
Free library / Occupational Safety and Health

Noise protection. Occupational Safety and Health

Occupational Safety and Health

Occupational Safety and Health / Legislative basis for labor protection

From a physical point of view noise is a mixture of sounds of different frequencies and intensities, propagating through solid, liquid and gaseous media.

From a physiological point of view, noise is any sound and / or combination of sounds that interferes with a person.

The audible range of sounds (noises) is from 20 to 20 Hz. Below 000 Hz - the region of infrasounds, above 20 Hz - the region of ultrasounds.

The human ear can perceive and analyze sounds in a wide range of frequencies and intensities. The boundaries of frequency perception significantly depend on the age of the person and the condition of the hearing organ. In middle-aged and elderly people, the upper limit of the audible region drops to 12-10 kHz.

The area of audible sounds is limited by two curves: the lower curve determines the threshold of audibility, i.e. the strength of barely audible sounds of various frequencies, the upper one is the threshold of pain, i.e. such a strength of sound at which a normal auditory sensation turns into a painful irritation of the organ of hearing.

The subjectively perceived intensity of a sound is called its loudness (physiological strength of sound). Loudness is a function of sound intensity, frequency and duration of the physiological features of the auditory analyzer. With increasing sound intensity, the ear reacts in approximately the same way to sounds of different frequencies of the sound range.

As characteristics of constant noise at workplaces, as well as to determine the effectiveness of measures to limit its adverse effects, sound pressure levels (in dB) in octave bands with geometric mean frequencies of 31,5 are taken; 63; 125; 250; 1000; 2000; 4000 and 8000 Hz.

In the hygienic assessment, noise is classified according to the nature of the spectrum and according to temporal characteristics.

According to the nature of the spectrum, noise is divided into:

broadband, with a continuous spectrum with a width of more than one octave;
tonal, in the spectrum of which there are pronounced discrete tones.

The tonal nature of noise for practical purposes (when monitoring its parameters at workplaces) is established by measuring in one-third octave frequency bands by exceeding the level in one band over the neighboring ones by at least 10 dB.

According to temporal characteristics, noise is divided into:

constants, the sound level of which during an 8-hour working day (work shift) changes over time by no more than 5 dBA when measured on the A scale of a sound level meter;
intermittent, the sound level of which during an 8-hour working day (work shift) changes over time by more than 5 dBA when measured on the A scale of a sound level meter.
Intermittent noises are subdivided, in turn, into:
fluctuating in time, the sound level of which continuously changes in time;
intermittent, the sound level of which changes in steps by 5 dBA or more, and the duration of the intervals during which the level remains constant is 1 s or more;
impulse, consisting of one or more sound signals, each with a duration of less than 1 s. At the same time, the sound levels in dBA, measured respectively on the time characteristics of the "impulse" and "slow" sound level meter, differ by at least 7 dBA.

Noise, being an informational hindrance to higher nervous activity in general, has an adverse effect on the course of nervous processes, increases the stress of physiological functions during labor, contributes to the development of fatigue and reduces the body's performance.

Among the numerous manifestations of the adverse effects of noise on the body, one can single out a decrease in speech intelligibility, unpleasant sensations, the development of fatigue, a decrease in labor productivity, and, finally, the appearance of noise pathology.

Among the various manifestations of noise pathology, the leading clinical sign is a slowly progressive hearing loss.

However, in addition to a specific effect on the hearing organs, noise also has an unfavorable general biological effect, causing shifts in the functional systems of the body. So, under the influence of noise, vegetative reactions occur, causing a violation of the peripheral circulation due to the narrowing of the capillaries, as well as a change in blood pressure (mainly an increase). Noise causes a decrease in immunological reactivity and overall body resistance, which is manifested in an increase in the level of morbidity with temporary disability (1,2-1,3 times with an increase in the level of industrial noise by 10 dB).

To reduce noise in industrial premises, various methods of collective protection are used: reducing the noise level at the source of its occurrence; rational placement of equipment; the fight against noise along its propagation paths, including changing the direction of noise emission, the use of sound insulation, sound absorption and the installation of noise silencers, acoustic treatment of room surfaces.

Noise protection must be ensured in industrial workplaces construction-acoustic methods:

rational, from an acoustic point of view, solution of the general plan of the object, rational architectural and planning solution of buildings;
the use of building envelopes with the required sound insulation;
the use of sound-absorbing structures (sound-absorbing linings, wings, piece absorbers);
the use of soundproof observation and remote control booths;
the use of soundproof casings on noisy units;
the use of acoustic screens;
the use of noise suppressors in ventilation, air conditioning systems and in aerogasdynamic installations;
vibration isolation of technological equipment.

Acoustic landscaping, the creation of optimal acoustic conditions in auditoriums, auditoriums of theaters, cinemas, palaces of culture, sports halls, waiting rooms and operating rooms of railway, air and bus stations should be provided:

rational space-planning solution of the hall (ratio of volume-linear dimensions);
the use of sound-absorbing materials and structures;
the use of sound-reflecting and sound-diffusing structures;
the use of enclosing structures that provide the required sound insulation from internal and external noise sources;
the use of noise silencers in forced ventilation and air conditioning systems;
the use of sound amplification, warning and information transmission systems.

To protect against noise, various personal protective equipment is also widely used: anti-noise headphones that cover the auricle from the outside; earmolds that cover the external auditory canal or adjacent to it; anti-noise helmets and helmets; anti-noise suits (GOST 12.1.029-80. SSBT "Means and methods of protection against noise. Classification").

When developing new and upgrading existing equipment, devices and tools, it is necessary to provide measures to limit the adverse effects of ultrasound on workers:

decrease in the intensity of ultrasound in the source of education due to the rational selection of equipment power, taking into account technological requirements;
when designing ultrasonic installations, it is not recommended to choose an operating frequency below 22 kHz in order to reduce the effect of high-frequency noise;
equipping ultrasonic installations with soundproof casings or screens, while there should be no holes and slots in the casing. Increasing the effectiveness of the sound-absorbing casing can be achieved by placing sound-absorbing material or resonator absorbers inside the casing;
placement of ultrasonic equipment in soundproof rooms or cabins with remote control;
equipment of ultrasonic installations with interlock systems that turn off the transducers when the casings are opened;
creation of automatic ultrasonic equipment for washing containers, cleaning parts, etc.;
manufacture of fixtures to hold the source of ultrasound or the workpiece;
use of a special working tool with a vibration-isolating handle.

Reducing the intensity of infrasoundgenerated by technological processes and equipment should be achieved through the use of a set of measures, including:

weakening of infrasound power at the source of its formation at the stage of design, construction, elaboration of architectural and planning solutions, layout of premises and placement of equipment;
isolation of infrasound sources in separate rooms;
use of observation booths with remote control of the technological process;
reducing the intensity of infrasound in the source by introducing special damping devices of small linear dimensions into the technological chains, redistributing the spectral composition of infrasound oscillations to higher frequencies;
sheltering equipment with casings having increased sound insulation in the region of infrasonic frequencies;
surface finishing of industrial premises with structures having a high sound absorption coefficient in the region of infrasonic frequencies;
reduction of equipment vibration if infrasound is of vibrational origin;
installation of special silencers that reduce infrasound on air intake shafts, exhaust ports of compressors and fans;
increasing the sound insulation of building envelopes in the area of infrasonic frequencies by increasing their rigidity through the use of non-planar elements;
sealing holes and cracks in the enclosing structures of industrial premises;
use of interference type infrasound silencers.

Authors: Fainburg G.Z., Ovsyankin A.D., Potemkin V.I.

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