| Natural phenomena bring huge disasters and losses to mankind,such as earthquakes,volcanic eruptions,mudslides,avalanches,the prediction of natural disasters is very urgent.In recent years,the detection of infrasound produced before the occurrence of natural disasters is one of the main methods of natural disaster prediction.The conventional infrasound detection method is to use high-precision and high-cost infrasound sensors to detect the infrasound in the atmosphere,it will reduce the requirement of infrasound sensor,reduce a lot of cost,deploy sensor network in a larger geographical area,and better and more accurately forecast the natural disaster with sound source located underground.In this paper,an underground infrasound detection method based on vibration detection is proposed,which is inspired by the paper of earthquake detection from space,the relationship between the acceleration detected by the accelerometer and the vibration is studied.In view of this,the following research was carried out in this paper:(1)In view of the problem of the relationship between the acceleration value detected by the accelerometer and the vibration,the working mechanism of the accelerometer is analyzed,and the characteristic is combined that the signal amplitude of MEMS sensor has no attenuation in the range below natural frequency,the relationship between the acceleration detected by the accelerometer and the vibration velocity is obtained,through which the subsurface acoustic waves can be detected by the accelerometer.(2)Through the analysis of the refraction law and attenuation characteristics of acoustic waves,compared with the traditional infrasound detection method,the method based on vibration detection has higher detection accuracy and fewer interference sources,on the detection of the required accuracy of the sensor requirements lower advantages.(3)In this paper,a general design scheme of subsurface infrasound detection device is proposed,the device is designed on the basis of the characteristics of the infrasound signals of natural disasters which are located underground by each sound source,and combined with the software and hardware system of embedded technology and the corresponding algorithm.In this design,the MMA7260 is selected to collect the analog voltage signal of the vibration signal produced by the underground sound wave,and the STC15F2K60S2 is analog to digital converted by the low pass filter and the amplifier circuit to process the signal,because the hardware filtering is not ideal in the case of extremely low frequency,the signal still needs to be filtered by software through the second-order low-pass filtering algorithm,then FFT(Fast Fourier transform)transform is used to get the spectrum characteristic of the vibration signal produced by the underground infrasound,and to judge whether there is the infrasound signal produced by natural disaster.The 6 ～ 20 Hz infrasound generator and 0.01 ～ 5Hz infrasound shaking table are used to test the device respectively,to verify the rationality of the underground infrasound detection method based on vibration detection.In this paper,through the experimental verification of the underground infrasound detection device,it is concluded that the test result of the device satisfies the relationship between the calculated acceleration value detected by the accelerometer and the vibration velocity value generated by infrasound,the rationality of the detection method of subsurface infrasound based on vibration detection is proved.In the future,the device is expected to conduct further research on subsurface infrasound produced by natural disasters with sound sources located underground.Compared with other mainstream infrasound sensors which detect infrasound by detecting the change of air pressure,a method of detecting infrasound by buried underground to detect underground vibration was innovatively proposed,the detection device of subsurface infrasound is made for this purpose.However,due to limited conditions,and the current research on the infrasound on the ground is less,the device lacks the comparison between the experimental results and the measured values of standard sensors. |
