The development of the transport and technological equipment is accompanied by the increasing of the size and the power of the machines, which tends to cause the growing of the low frequency rates in their noise sound spectra. This sound of low frequency is called infrasound and is not a completely studied phenomenon of the new industrial environment.

The infrasound is the sound of low frequencies, which are lower than 20 Hz. “Infrasound” is the word of the Latin origin. “Infra” means “lower, under”. The infrasound is natural and can be heard in the atmosphere, in the sea or in the forests. The source of the infrasound vibrations can be the thunder or the explosions.

The infrasound almost can’t be absorbed by the objects. So it is spread for the larger territories in comparison with the sound of higher frequencies.

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