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10 INDUSTRIAL NOISE

10.1 Characteristics of N oise

Industrial noise is any unwanted sound to a human, which hinders the
perception of useful signals.

There are the next basic parameters of the noise:
The amplitude of the oscillation is the maximum deviation from the initial
position of the particles of the environment that conduct sound.
Sound pressure is a variable pressure that occurs in addition to the
atmospheric pressure in the environment through which the sound waves are spread.
The speed of sound is the distance at which the wave process can spread in
one second.
The wavelength of a sound is the distance between adjacent identical parts of
a wave - for example, between adjacent compressions.
The power of sound (intensity) is the amount of energy that passes in the result
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of sound spread through an area of 1m per unit of time.
The frequency content of noise is a collection of sound frequencies contained
in it.
The range of normal perception for the young person is 20–20,000 Hz.
The whole frequency range is divided into sets of frequencies called bands.
Each band covers a specific range of frequencies. For this reason, a scale of octave
bands and one-third octave bands has been developed. A band is said to be an
octave in width when the upper band frequency is twice the lower band frequency. A

one-third octave band is defined as a frequency band whose upper band-edge
frequency (f2) is the lower band frequency (f1) times the cube root of two.
All octave bands and one-third octave bands characterized by the center
frequencies that are standardized notation and used to characterize the frequency
dependence of noise:

1/2
fc= (f1f2) ,
where: fc is center frequency and f1 and f2 are lower and upper band edges
respectively, Hz - 31.5, 62, 125, 250, 500, 1K, 2K, 4K, 8K, 16K

Interference is the process of imposition of the sound waves of the same
frequency.
Diffraction is the process of sound waves rounding of the finite size obstacles.
Resonance is the process of a sharp amplitude increase due to the coincidence
of the sound frequency with the natural frequency of oscillation.
Sound volume or noise (loudness level L). The unit of the loudness level is
fon.
Only at the frequency of 1000 Hz units of the Sound pressure level in dB
match with units of loudness level in fon.
Sound power of the sound source P is the total amount of sound energy
radiated by a source of noise into the environment per unit of time.

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