Research And Experiment On Signal Processing Method Of Underwater Acoustic Beacon With Low Signal To Noise Ratio

Black box is the most important instrument for data recording in the air crash.,whether or not the black box can be found has become a key issue in unraveling the mystery of missing flights.Acoustic beacon is installed in the black box,and the underwater acoustic signal should be detected and located through acoustic signal processing method.However,the signal of acoustic beacon will be inundated by the background noise of the ocean environment and difficult to identify,and the transmission loss of ocean will cause a severe attenuation of the signal during long distance transmission.These factors make it difficult for existing methods of underwater acoustic signal processing like Fourier transform and Wavelet transform to identify underwater*acoustic beacon signals with long range and low SNR.Therefore,a new algorithm for signal enhancement is proposed in this paper,the source signal can be enhanced and amplified without changing the signal waveform.And a kind of underwater acoustic beacon signal processing system is designed and tested.In this paper,a signal enhancement algorithm based on random decrement technique is proposed.It is dislocation superimposed method.Two superposition methods are analyzed which are superposition of the adjacent pulses and superposition of the same time interval.It uses the staggered superposition method and the cross correlation function to extract the sound beacon signal with noise interference.The dislocation superimposed method and cross correlation function are used to extract the acoustic signal with noise interference.First,we select the superposition starting point and determine the length of the intercepted signal segments according to two different superposition methods.Then we linearly superimpose each intercepted signal segment to complete the extraction of underwater acoustic beacon signal.Finally,we perform cross-correlation analysis and energy analysis on the signal to determine the accuracy of the intercepted signal.Based on the signal enhancement algorithm,a signal processing module for underwater acoustic beacon is designed and it mainly consists of hydrophone,preamplifier,digital storage oscilloscope,circuit development board and display module.The circuit board uses the STM32 series of microcontrollers.By detecting the signal level of four positions,the system calculates the propagation distance of four points,thereby solve the position information of the underwater acoustic beacon signal.During the test process,different kinds of signal processing methods are used to process the collected acoustic beacon signals.After comparison and analysis of the data,the results show that dislocation superimposed method can keep the energy of the signal under consideration and the noise part is obviously weakened.After several times of superposition,the correlation between the synthesized signal and the sinusoidal signal reaches more than 80%,and the extraction effect is significantly better than other methods.The acoustic beacon signal extracted by the dislocation superimposed method has a high accuracy waveform and the method is simple and easy.