Estimates of a relative delay time of signals through analysis of their forms Sergey Kulichkov, Aleksey Chulichkov Dmitrii Demin A.M.Oboukhov Institute of Atmospheric Physics RAS, Pyzhevskii 3, Moscow , Russia Supported by RFBR projects №№ ,

OBJECTIVES ♦ T o develop method of processing of infrasound signals when conventional methods (correlation techniques, etc) are not so effective ♦ I ntensive noise (informative part of a signal less then main signal period) ♦ T o determine azimuth and grazing angles of different parts of infrasonic signals corresponding to different reflection heights ♦ T o processing of infrasonic signals having wave lengths less than the distance between acoustic microphones.

Time variations of the double amplitude of recorded signals (curve 1); reflections height H (curve 2), and the quantity F 1/2 /sin 3 Ө (curve 3) - top. Infrasonic signals recorded at a distance of 300 km to the north of the explosions equivalent to 20–70 t of TNT implemented on October 14, bottom

Infrasonic signals having wave lengths less than the distance between acoustic microphones.

Methods to processing of infrasound data Morphological analysis (analysis of the signals form) Identification (persons, finger-prints, etc.)

MODEL

Top Infrasonic signals observed at three microphones. Basic signal – black line (part of a signal between vertical lines). Bottom Adjacency of different parts of signals at different microphones to basic part of a signal (black line between vertical lines) in logarithmic scale. Left – present method; Right –method of maximal plauxibility

Top Infrasonic signals observed at three microphones. Time interval of signals part – red arrow (1.5 sec) Bottom Times delay between signals (blue and black lines) obtained by using of mrphological (blue) and correlation methods (green).

Top Infrasonic signals observed at three microphones. Time interval of signals part – red arrow (6 sec) Bottom Times delay between signals (blue and black lines) obtained by using of mrphological (blue) and correlation methods (green).

Top Infrasonic signals observed at three microphones. Time interval of signals part – 2 sec. Bottom Asimuths of arrivals obtained by using of morphological (blue and black) and correlation methods (red).

Top Infrasonic signals observed at three microphones. Time interval of signals part – 2 sec. Bottom Grazing angless of arrivals obtained by using of morphological (blue and black) and correlation methods (red).

Top Infrasonic signals observed at three microphones. Time interval of signals part –. Bottom Asimuths (black line) and grazing angles (red line) of arrivals obtained by using of morphological methods.

CONCLUSIONS ♦ The method of morphological analysis to processing of infrasound data are presented ♦ The method is based on an analysis of signal forms ♦ The method is especially efficient in analyzing isolated signal fragments whose durations are shorter than a characteristic period of signal ♦ It is suggested that this method may be used for the problems of infrasonic explosion monitoring, when an informative signal is recorded against the background of an intensive natural acoustic noise

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