Research On The Characteristics Of Thunder Signal

Thunder is generated by the attenuation of shock wave during its transmission process which originates from the rapid expansion of air around the lightning. It is a kind of natural phenomenon. It is also a sound wave, which has certain energy, so studying its mechanism of action on the plant breeding will become a new application field. The time domain, frequency domain and time-frequency characteristics of the thunder were researched in this thesis, providing a theoretical basis for the study of the effect of thunder on the plant breeding.Complexity of thunder signal increases the difficulty to study the characteristics. According to the signal processing methods, the following contents were studied:(1)The dissemination process of thunder mixes with a lot of noise, so it must be through the noise reduction processing. The de-noising effect of db wavelet, coif wavelet and sym wavelet were compared by comparing the signal-to-noise ratio (SNR) and mean square error (MSE) of them, and then it was found that the de-noising effect of coif5 wavelet is the best when the decomposition layer is 5.(2)The time domain and frequency domain characteristics of thunder were analyzed through the normalized short-time energy and classic Welch method, Burg method. It was found that the energy of thunder is concentrated in the low frequency part within 0-2000Hz.(3)The simple analysis of power spectrum can only provide the approximate range of thunder energy distribution, in this thesis, Hilbert-Huang transform (HHT) was used to analyze finer time-frequency characteristics on the basis of traditional time-frequency analysis methods including short time Fourier transform, Wigner-Ville distribution and rearrangement spectra. The time-frequency information of thunder can be expressed accurately by Hilbert spectrum. The time period of main energy of the thunder was obtained and the energy reached the maximum at about 200Hz.Through this study, wavelet transform and HHT can be combined to analyze the thunder signal, and then thunder can be applied to cultivate plants seed, promoting seed germination and increasing the seed yield.