Spectrogram, part 3

In nature, there is also infrasound whose a major source is wind. How infrasound caused by the wind stands out?

In a figure below, a strong ground wind causes noise in the low frequency regions. A particularly strong variation is on very low frequencies, which can be detected best in the time domain measurements. There is no noticeable periodicity in wind-induced infrasound. The figure below shows wraparound point (1.), where there is infrasound caused by strong ground wind.

Infrasound produced by wind turbines can be seen very clearly as vertical stripes pointed by white arrows (2.).

Ground wind means wind near the ground level. It should be noted that even if there is wind in higher level and the wind turbines are in operation, there is not always hardly any wind on the surface of the ground . In the figure above, it can be seen that during . 00: 00 – 14: 00 period there is little wind on the Earth’s surface, but between 14: 00 – 22: 20 wind is blowing hard in the surface of the Earth.

Wind turbine infrasound signal is covered partly by the noise caused by the strong ground wind.