Research On Suppression Of The Atmospheric Noise And Environmental Noise In The Signal Of The Laser Listening System

In this paper, in order to advance the ability of the laser listening system to resist the atmospheric disturbance and improve the surweillant signal's SNR or definition, the research is aimed at the atmospheric noise and environmental noise.In this paper, the soundex using laser bean modulated in intensity is advanced to suppress the atmospheric noise. First, the assistant carrier frequency modulates the laser bean in intensity, speech signal is modulated to the assistant carrier frequency in phase, the receiver detects the laser's intensity. Second, the atmosphere noise is cleared up by high-through filtering. Last, speech signal is demodulated from the assistant carrier wave modulated in phase. In generic instance, the method can avoid the atmospheric noise, even the atmosphere noise is very large (modulate index to laser bean reaching 1), it is anticipated that the signal's SNR can be kept OdB upwards.In this paper, an optimum FIR (Finite Impulse Response) linear filter is realized in real time. The filter's total number of bands can reach 7. The frequency of reject bands and pass bands, the length of the filter and the total number of bands can be adjusted in real time, the demand to suppress interceptive system's noise in real time can be satisfied.Basing on the theory of phonetics and the short-lived calm speciality of speech, a method enhancing speech by prolonging speech in duration is advanced. Speech signal is divided into a series of small segments that are short-lived calm. These segments is copied, and then is spliced, so the duration of speech is prolonged and speech is enhanced. The result of experiments indicates, even the duration of speech have been doubled, the character of speech's frequency spectrum keep steady, few new noise is imported, speech will not be distorted, the effect of speech enhancement is favorable.