Infrasound Characteristics Research Articles

Research on the Response Characteristics and Identification of Infrasound Signals in the Jialongcuo Ice Avalanche, Tibet

Due to the inability of remote sensing satellites to monitor avalanches in real time, this study focuses on the glaciers in the rear edge of Jialongcuo, Tibet, and uses infrasound sensors to conduct real-time monitoring of ice avalanches. The following conclusions are drawn: (1) In terms of waveform, compared to background noise, ice avalanche events have a slight left deviation and a slightly steep shape; compared to wind, rain, and floods events, ice avalanche events have less obvious kurtosis and skewness. (2) In terms of frequency distribution, the infrasound frequency generated by ice avalanche events is mainly distributed in the range of 1.5 Hz to 9.5 Hz; compared to other events, ice avalanche events differ some in frequency characteristics. (3) The model based on information entropy and marginal spectral frequency distribution characteristics of infrasound have higher accuracy in signal classification and recognition, as they can better represent the differences between infrasound signals of different events than other features. (4) Compared with the K-nearest neighbor algorithm and classification tree algorithm, the support vector machine and BP (Back Propagation) neural network algorithm are more suitable for identifying infrasound signals in the Jialongcuo ice avalanche. The research results can provide theoretical support for the application of infrasound-based ice avalanche monitoring technology.

Study on the Coupling Characteristics of Infrasound–Temperature–Gas in the Process of Coal Spontaneous Combustion and a New Early Warning Method

ABSTRACT The phenomenon of coal spontaneous combustion poses a serious threat to mine safety, and monitoring and warning of coal spontaneous combustion has become an important issue that needs to be urgently addressed in coal mines. The current monitoring and early warning methods for coal spontaneous combustion have their limitations, and a single indicator cannot accurately mark the degree of coal spontaneous combustion danger inside the goaf. Therefore, this article proposes a new method for monitoring coal spontaneous combustion through infrasound waves. Infrasound waves have advantages such as low attenuation and long transmission distance. However, current research on monitoring and warning coal spontaneous combustion in goaf through infrasound waves is not yet complete, and there is a lack of research on the characteristics of infrasound signal changes during coal spontaneous combustion. Based on this, the article first tested the characteristic temperature and release changes of indicator gases (CO, C2H4) through thermogravimetric experiments and coal oxidation and heating experiments. Then, the generation and variation of infrasonic signals during coal spontaneous combustion (CSC) was studied and analyzed using a self-designed CSC infrasonic testing system. The results showed that obvious infrasound signals could be generated during the CSC process, there is a good mapping relationship between signals and temperature. Furthermore, the analysis revealed the inherent relationship between the infrasonic signal, temperature, and indicator gas of coal at different oxidation stages. The research in this article has promoted the use of infrasound waves for temperature inversion and promoted the development of multi-parameter analysis and early warning of CSC, which is of great significance for the field of CSC monitoring.

Global shockwaves of the Hunga Tonga-Hunga Ha’apai volcano eruption measured at ground stations

The eruption of the Tonga volcano created globally propagating spherical shockwaves in the atmosphere. Analyses are done to data from two southern U.S. stations of the author sampling at 3-21s intervals and 189 weather stations at 1-5min intervals. The shockwaves arrived from two routes in the atmosphere: the shortest spherical arc and the longer spherical arc through the antipole. In most stations, signals up to the 6th path of shockwaves were recorded as the waves traveled around the globe multiple times. The speed of shockwaves is estimated to be 309.5± 2.9m/s, consistent with the speed of sound at the top of the troposphere where a waveguide exists. Discussion is made on the post-shockwave ringing of 4-8min as higher amplitude oscillations above the level of pre-shockwaves background noise. A theoretical wave dispersion is derived which verifies that the spherical shockwave's phase speed is the same as the speed of sound.

Infrasound generated by meteorological fronts as a background for infrasound monitoring of explosions

The results of study of temporal variations of the characteristics of infrasound (amplitudes, coherences, grazing angles, azimuths and horizontal phase speeds) detected during a passage of warm and cold fronts through the networks of microbarometers in the Moscow region are presented. .Infrasound radiated during periods of weather changes is an almost continuous background against which infrasound monitoring of explosions in the atmosphere is carried out. The significant differences observed in the characteristics of infrasound from warm and cold fronts are found. Such differences must be taken into account when detecting infrasound precursors of atmospheric storms. A possible aerodynamic mechanism for the generation of infrasound caused by the turbulent air flow around the geometric irregularities of the surface of meteorological front is proposed. [Work supported by RSF Grant No. 21-17-00021.]

Infrasound characteristics of nontornadic and tornadic thunderstorms using high-resolution simulations

There has been increased interest in improving severe weather detection by supplementing NOAA's WSR-88D radar network with an infrasound observation network, which may be able to detect distinct sub-audible signatures from tornadic thunderstorms. While there is evidence that tornadic thunderstorms exhibit observable infrasound signals, what is not well-understood is whether these infrasound signals are unique to tornadic storms compared to nontornadic storms or whether there is any useful signal prior to tornadogenesis (which would be most relevant to NWS forecasters). In this presentation, we will present the results of high-resolution simulations of severe thunderstorms, specifically tailored to represent acoustic wave propagation with frequencies of 0.1 to 1 Hz. The spectral analysis of pressure perturbations generated by a nontornadic and tornadic supercell thunderstorm will be compared against each other. Two additional sensitivity tests that employ different microphysics schemes (i.e., the representation of precipitation within the storm) will be discussed, since prior work has indicated that the melting of precipitation is a dominant contributor to infrasound generation in thunderstorms. So far, preliminary results suggest that there are no discernible differences in infrasound observed in the vicinity of tornadic versus nontornadic supercell thunderstorms prior to tornadogenesis.

The experimental research on response characteristics of coal samples under the uniaxial loading process

In order to study the response characteristics of infrasound in coal samples under the uniaxial loading process, coal samples were collected from GengCun mine. Coal rock stress loading device, acoustic emission tested system and infrasound tested system were used to test the infrasonic signal and acoustic emission signal under uniaxial loading process. The tested results were analyzed by the methods of wavelet filter, threshold denoise, time–frequency analysis and so on. The results showed that in the loading process, the change of the infrasonic wave displayed the characteristics of stage, and it could be divided into three stages: initial stage with a certain amount infrasound events, middle stage with few infrasound events, and late stage gradual decrease. It had a good consistency with changing characteristics of acoustic emission. At the same time, the frequency of infrasound was very low. It can propagate over a very long distance with little attenuation, and the characteristics of the infrasound before the destruction of the coal samples were obvious. A method of using the infrasound characteristics to predict the destruction of coal samples was proposed. This is of great significance to guide the prediction of geological hazards in coal mines.

The study of sudden stratospheric warmings using infrasound

Infrasound has a long history in monitoring SSWs. Several pioneering studies have focused on the various effects of a major warming on the propagation of infrasound, described throughout this chapter. A clear transition can be denoted from observing anomalous signatures towards the use of these signals to study anomalies in upper atmospheric specifications. First studies describe the various infrasonic signatures of a major warming. In general, the significant change in observed infrasound characteristics correspond to summer-like conditions in midwinter. More subtle changes are denoted during a minor warming, recognizable by the presence of a bidirectional stratospheric duct. A combined analysis of all signal characteristic unravels the general stratospheric structure throughout the life cycle of the warming. From then on, infrasound observations are used to evaluate the state of the atmosphere as represented by various NWP models. A new methodology, comparing regional volcano infrasound with simulations...

B10 2009年の桜島昭和火口の噴火活動にともなう地震・空振波形について(火山の流体振動,口頭発表)

B10 2009年の桜島昭和火口の噴火活動にともなう地震・空振波形について(火山の流体振動,口頭発表)

Study on precursory characteristics of granite failure based on infrasonic energy

To study signal characteristics of precursory infrasound of granite failure, coal-rock stress loading device and infrasound acquisition device were adopted to perform infrasound test in uniaxial loading process for granite samples. Wavelet filtering, infrasonic energy methods were used to process and analyze the test results. The results show that the infrasonic waves caused by the failure of rock samples are mainly in the middle and low frequency. Moreover, in the loading process, the ratio of relative energy of infrasound in different frequency sections and the total relative energy of the whole low frequency section both exhibit significant regularity of stage change, which is in consistent with the compaction stage, elastic stage, plastic stage of rock deformation. Additionally, the precursory characteristics of infrasound before rock failures are prominent and easy to be recognized. Meanwhile, infrasonic wave has the advantage of low attenuation in propagation process, which grants the superiority of infrasound prediction technology. A new method of rock failure prediction based on infrasound is formed, which provides an important reference for rock damage prediction in coal mining process.

The interaction between infrasonic waves and gravity wave perturbations: Application to observations using UTTR Rocket Motor Fuel Elimination Events

AbstractInfrasonic waves propagate at long ranges through atmospheric ducts resulting from the stratification of atmospheric properties. In order to study the infrasonic wave propagation, we resort to atmospheric specification combining Numerical Weather Prediction and climatological models. However, these models do not describe small‐scale variability such as perturbations associated to the presence of internal gravity waves. These waves play an important role in the atmospheric dynamic by transferring momentum to the mean flow at critical levels and at wave‐breaking altitudes. In this study we intend to describe the interaction of infrasonic waves with internal gravity waves in order to understand the extended wave trains observed in broadband infrasound signals. We use a numerical model for the propagation of internal waves to generate realistic perturbations of the background atmospheric states. By using a linear full‐wave model of infrasound propagation, our goal is to ultimately relate infrasound characteristics to internal waves properties. We apply those numerical models to different atmospheric mean states including gravity wave perturbations and compare the simulations to infrasound signals recorded from rocket motor fuel elimination events at the Utah Test and Training Range (UTTR). Our results, based on an intensive simulation of infrasound waveforms, show that combining atmospheric background with gravity wave propagation model is relevant to explain, to first order, the behavior of the infrasound field at the distance of the first stratospheric arc. In particular we obtain a better match between pulse duration and peak‐to‐peak amplitude along the stratospheric arc. Such study supports the use of gravity wave simulation in conjunction with infrasound modeling in order to improve gravity wave parameterization in Numerical Weather Forecasting.

The interaction between infrasonic waves and gravity waves perturbations: Application to explosions at the Utah test and training range

Infrasonic waves propagate at long range through atmospheric ducts resulting from the stratification of atmospheric properties. These ducts are characterized by their spatio-temporal variability. Hence, infrasonic waves integrate information upon the atmosphere along their propagation paths. In order to study infrasonic wave propagation, we resort to atmospheric specification combining numerical weather prediction and climatological models. However, due to the lack of observations these models fail to describe small scale variability such as perturbations associated to the presence of internal gravity waves. These waves play an important role in the atmospheric dynamic by transferring momentum to the mean flow at critical levels and at wave-breaking altitudes. In this study, we intend to describe the interaction of infrasonic waves with internal gravity waves in order to understand the long-tail behavior observed in infrasound broadband signals. We developed a model for the propagation of internal waves used to generate realistic perturbations of the background atmospheric states. By using a linear full-wave model of infrasound propagation, our goal is to ultimately relate infrasound characteristics to internal waves properties. We apply those numerical models to infrasound observations recorded during the 2010 deployment of the Utah Test and Training Range (UTTR) experiment.

On the interaction of infrasonic waves with internal gravity waves perturbations

Infrasonic waves propagate at long range through atmospheric ducts resulting from the stratification of atmospheric properties. These ducts are characterized by their spatio-temporal variability. Hence, infrasonic waves integrate atmospheric information along their propagation paths. In order to study infrasonic wave propagation, we resort to atmospheric specification combining Numerical Weather Prediction and climatological models. However, due to the lack of observations, these models fail to describe small scale variability such as perturbations associated to the presence of internal gravity waves. These waves play an important role in the atmospheric dynamic by transferring momentum to the mean flow at critical levels and at wave-breaking altitudes. In this study we intend to describe the interaction of infrasonic waves with internal gravity waves in order to understand the long-tail behavior observed in infrasound broadband signals. We developed a model for the propagation of internal waves used to generate realistic perturbations of the background atmospheric states. By using a linear full-wave model of infrasound propagation, our goal is to ultimately relate infrasound characteristics to internal waves properties.

Relation of the infrasound characteristics and the continuous steel bridge vibration modes generated by the vibration of moving heavy trucks

As heavy trucks pass over highway bridges, bridge vibration occurs and generates infrasound. General trucks in Japan with rear leaf suspension have whole body vibration (suspension spring vibration) frequencies of about 3 Hz. Also, the frequencies of the wheel vibration (tire spring vibration) are about 10–20 Hz. The continuous steel highway bridges with middle span length have vibration modes with the same phase in each span at the frequencies of about 3 Hz and also have those with the secondary mode shape at the frequencies of about 10–20 Hz. Truck vibrations and bridge vibrations are closely related. In this work, vibration tests are conducted using a heavy test truck for two cases of infrasound complaints in order to investigate the relation between the continuous steel bridge vibration modes generated by the vibration of moving heavy trucks and its infrasound characteristics. As a result of the examination, two types of bridge vibration modes are caused by the vibrations of a moving heavy truck. Moreover, the bending vibration modes with the same phase in each span have the most powerful infrasound pressure, since each span vibrates with the same phase. Two countermeasures, including viscoelastic damper at the end of the girders and extended deck method, are proposed to reduce the amplitude of bridge vibration and its infrasound.

A global study of volcanic infrasound characteristics and the potential for long-range monitoring

Volcanic infrasound from explosive eruptions is detectable at distances up to 1000 s of km and is often recorded on the International Monitoring System (IMS) infrasound network. Though infrasound produced by individual volcanoes has previously been studied, more general relationships between infrasound characteristics and eruption parameters remain unclear. Therefore, using a dataset comprising 110 events at 39 globally distributed volcanoes, we assess the ability of the IMS to monitor remote volcanoes and investigate whether volcanic infrasound exhibits consistent trends across a range of eruption styles and intensities. Acoustic pressure amplitude and frequency content of the volcanic infrasound were measured, and acoustic energy was also calculated. These were compared, along with the maximum distance of detection for each event, to the maximum plume height reported for the event, which was used as a proxy for event intensity. Of the events investigated 62% were detected by at least one infrasound station. The maximum distance at which an event was detected generally increased with the plume height, and infrasound produced during the eruption of Manam, PNG in January 2005, which produced a plume which rose over 20 km above the summit, was detected at a distance of 10,671 km. Total acoustic energy and acoustic pressure amplitude (corrected for geometrical spreading) increased with plume height, whilst the lowest frequency present in the volcanic infrasound decreased. Additionally, relationships seen between infrasound characteristics and eruption plume height indicate that analyses of this data alone could constrain vital estimates of plume heights for otherwise un-observed eruptions. Taken together these findings indicate that if made available for this purpose in the future, the IMS infrasound network could complement existing monitoring techniques by detecting and characterising eruptions at remote volcanoes which often have no local monitoring networks.

Characteristics of infrasound and its influence on workers in working environment of certain thermoelectricity works and department

To study the characteristics of infrasound and its effects on the workers at power plants. The audible noise and infrasound in three thermoelectricity plants were measured and by using Symptom Checklist 90 (SCL-90), the subjective sensation, and the physiological indices were compared between exposed workers and controls. The infrasound levels were different at different measure sites of the three thermoelectricity works ranging from 40 to 98 dB. There was still 40 approximately 80 dB infrasound even when the soot blower stopped running. Different apparatus produced different infrasound levels with the highest ranging from 62 to 115 dB. A single frequency (16 Hz) infrasound was produced in certain department during working hour with sound pressure levels of 110 to 120 dB, but the audible noise sound pressure level was less than 70 dB. There was no significant difference in the indices representing vision fatigue and neurobehaviour function between exposed workers and controls. Workers at certain department experienced evident subjective sensation of neurobehavioral dysfunction, and the scores of somatization, depression, hostility, phobic anxiety, and psychotism in the SCL-90 were significantly higher in the exposed group than in the control and the norm in China (P < 0.05). Infrasound is ubiquitous in the working environment, but usually, the noise levels are less than 120 dB. In some special production department, there is persistent infrasound above 110 to 120 dB. No obvious health effects are found among those who are exposed to infrasound below 100 dB. However, the workers who are chronically exposed to infrasound above 110 to 120 dB present notable subjective sensation of autonomic neurobehavioral dysfunction, and their psychological health status is not as good as those in the control and those in the domestic normal pattern.

Infrasonic and seismic signals from explosions in Northwestern Europe

Large explosions often generate both seismic and infrasound signals that can be detected over large ranges, i.e., hundreds of kilometers. Ground truth of such explosions is available from direct observations and/or seismic signals and can be used to get insight in the propagation of infrasound. Long range infrasound propagation is controlled by the state of the atmosphere. Tropospheric, stratospheric, and thermospheric ducts might exist and have implications on the signal characteristics and their detectability. In this study, we will show results of studies on explosions in Northwestern Europe using both seismic and infrasound data. These observations are used to derive source characteristics like: location, origin time and yield. Furthermore, the propagation characteristics of infrasound will be addressed.

Study on Characteristics of Infra Sound Radiated from Road Bridge

This paper describes characteristics of infra sound radiated from elevated road structure by measurement. Sound pressure levels along road are 70-90dB. In frequency characteristics, two peaks appear. One peak is at 2-6Hz, and the other is at 9-16Hz. Peak frequency at 2-6Hz is proportional to the reciprocal number of the length of road structure. On the other hand, peak frequency at 9-16Hz is not related the road structure length. Sound radiation coefficient by vibration plate is obtained by theoretical equation. At 2-6Hz, the sound radiation loss of concrete plate with road surface is smaller than the one of steel plate with I-type gilder.

An Instrument for the Measurement of Infrasounds and Subsonic Disturbances in the Atmosphere

The physical properties and propagation characteristics of infrasound and subsonic disturbances in the atmosphere determine the technique and instrumentation of their measurements. Infrasounds are characterized by their propagation velocities close to acoustic velocity but frequencies less than that of audible sound, while the subsonic disturbances refer to disturbances having both frequency and propagation velocity below those of audible sound. The sources of both types of disturbances include many geophysical phenomenon as well as powerful explosions, supersonic vehicles etc. A microbarograph recording system has been described to record pressure variations caused by these disturbances. The system includes the micrograph transducer, its calibration assembly and associated electronics. The transducer uses sensitive bellows to sense the atmospheric pressure and a variable reluctance transducer converts the movements of the bellows into electrical signal. The frequency response of the system is determined ...