Noise

Noise - a set of non-periodic sounds of varying intensity and frequency. From a physiological point of view, noise is any unfavorably perceived sound .

Spectrum

Noises are divided into stationary and non-stationary.

By the nature of the spectrum

By the nature of the spectrum, noise is divided into:

• broadband noise with a continuous spectrum of a width of more than 1 octave;
• tonal noise, in the spectrum of which there are pronounced tones. A pronounced tone is considered if one of the one-third octave frequency bands exceeds the others by at least 10 dB ^[1] .

Frequency (Hz)

According to the frequency response, the noise is divided into:

• low frequency (<300 Hz)
• mid-frequency (300-800 Hz)
• high frequency (> 800 Hz)

By temporal characteristics

• stationary ;
• non-stationary:
  • hesitant;
  • intermittent;
  • impulse.

By nature

• Mechanical
• Aerodynamic
• Hydraulic
• Electromagnetic

Selected noise categories

• White noise is stationary noise, the spectral components of which are uniformly distributed over the entire range of frequencies involved.
• Color noise - some types of noise signals that have certain colors, based on the analogy between the spectral density of a signal of an arbitrary nature and the spectra of various colors of visible light.
• Pink noise (in building acoustics), in which the sound pressure level changes in the octave frequency band. Designation: C ;

To quantify noise use averaged parameters determined on the basis of statistical laws. Noise meters , frequency analyzers , correlometers, etc. are used to measure noise characteristics.

The noise level is most often measured in decibels (20 dB - sound pressure 10 times higher than the standard threshold of audibility; 40 dB - 100 times ...).

Sound power in decibels:

• Talk: 40–45
• Office: 50-60
• Street: 70-80
• Factory (heavy industry): 70-110
• Chain Saw : 100
• Jet Launch: 120
• At the bell of the vuvuzela : 130

To measure acoustic noise, Steven Orfield founded the Orfield Laboratories in South Minneapolis. To achieve exceptional silence, the room uses fiberglass acoustic platforms a meter thick, double walls made of insulated steel and concrete 30 cm thick. The room blocks 99.99 percent of external sounds and absorbs internal ones. This camera is used by many manufacturers to test the volume of their products, such as heart valves, the sound of a mobile phone display, the sound of a switch on the car dashboard. It is also used to determine sound quality. ^[2]

Sources of acoustic noise can be any vibrations in solid, liquid and gaseous media; In engineering, the main sources of noise are various engines and mechanisms . The following classification of noise by source of origin is generally accepted:

• mechanical;
• hydraulic;
• aerodynamic;
• electric.

The increased noise of machines and mechanisms is often a sign of the presence of malfunctions or irrationality of structures in them. Sources of noise in the workplace are transport, technological equipment, ventilation systems, pneumatic and hydraulic units, as well as sources that cause vibration .

Non-Acoustic Noises

• Radio-electronic noise - random fluctuations in currents and voltages in electronic devices, arise as a result of uneven emission of electrons in electrovacuum devices ( shot noise , flicker noise ), uneven generation and recombination of charge carriers (conduction electrons and holes) in semiconductor devices, and thermal motion of carriers current in conductors ( thermal noise );
• thermal radiation of the Earth and the Earth’s atmosphere , as well as planets, the Sun, stars, interstellar medium, etc. ( space noises );
• on the Earth also there are inexplicable noise phenomena (see. Sound anomalies ).

Per person

The noise of the sound range slows down a person’s reaction to signals received from technical devices, this leads to a decrease in attention and an increase in errors when performing various types of work. Noise depresses the central nervous system (CNS) , causes changes in respiration rate and pulse rate, contributes to metabolic disorders, the occurrence of cardiovascular diseases, stomach ulcers , hypertension.
When exposed to high levels of noise (more than 140 dB), tympanic membranes may rupture, shell shock , and even higher (more than 160 dB) death is possible.

The noise produced by wind farms also affects the human environment and nature.

Hygienic noise regulation

To determine the permissible noise level at workplaces, in residential premises, public buildings and residential areas, GOST 12.1.003-2014 is used. SSBT “Noise. General safety requirements ”, SN 2.2.4 / 2.1.8.562-96“ Noise at workplaces, in residential, public buildings and residential buildings ”. Sound range noise is normalized by the limit spectrum of the noise level and by dBA. This method sets the maximum permissible levels (PDU) in nine octave bands with geometric mean frequencies of 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 Hz.

Sanitary norms SN 2.2.4 / 2.1.8.562-96 Noise at workplaces, in premises of residential, public buildings and in residential areas

To the nature

Underwater

Recently, there has been evidence that powerful engines of ships and submarines , and especially sonars and sonars, greatly interfere with underwater inhabitants using the sonar method of communication and search for prey. Particularly affected are some species of whales and dolphins .

Some previously unexplained cases of mass death of whales, their “throwing ashore” have now found an explanation. In some cases, the phenomenon may be associated with military exercises , during which mammals stall and lose their ability to navigate.

• Signal to noise ratio
• Noise suppression
• Sound level meter
• Noise pollution
• Industrial noise
• Vibration
• Silence
• NIOSH noise protection recommendations

• Bysko M.V. Shumologiya // "Media music ". - 2014. - No. 3 .
• Taylor R. Noise. - M .: Mir , 1978.
• SN 2.2.4 / 2.1.8.562-96 Noise at workplaces, in premises of residential, public buildings and in residential areas "
• Guidelines for the hygienic assessment of working environment and labor factors. Criteria and classification of working conditions. Leadership. R 2.2.2006 - 05
• MUK 4.3.2194-07 Monitoring the noise level in residential areas, in residential and public buildings and premises
• GOST 31296.1-2005 Noise. Description, measurement and assessment of noise on the ground.

• Volume levels of various noise sources
• Modern cars are getting quieter
• The noise around us // Science and Life. - 2006. - No. 4.