Frequency Analysis of Thunder Features

Abstract

Acoustic signatures of thunder can be used in understanding some properties of lightning channels. Basic features of thunder signal are qualitatively classified as Peals, Claps and Rumble. In studies [1] and [4], attempts have been made to recognize these features quantitatively. To strengthen previous findings, above features were analyzed using Stransformation in this study. Characteristics of Peals, Claps and Rumble are directly affected by the acoustic energy, channel tortuosity, the interference of distinct parts of the channel, channel orientation relative to the observer and attenuation of high frequencies during the propagation. The fundamental frequency of audible thunder appears less than 250 Hz. Stransformation was introduced to estimate the fundamental frequencies and mean frequencies of thunder features with a level of significance. The elapsed time of peals and claps depends with the intensity level and the frequency composition of the fluctuation. The mean fundamental frequency of rumbles is 63 Hz.