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Array Theory
Published in Lawrence J. Ziomek, Fundamentals of Acoustic Field Theory and Space-Time Signal Processing, 2020
An array can be thought of as a sampled aperture, that is, an aperture that is excited only at points or in localized areas. An array consists of individual electroacoustic transducers called elements. When an array is used in the active mode, the electroacoustic transducers are used as transmitters, converting electrical signals (voltages and currents) into acoustic signals (sound waves). When an array is used in the passive mode, the electroacoustic transducers are used as receivers, converting acoustic signals into electrical signals for further signal processing. In underwater acoustic applications, when an electroacoustic transducer is used as a receiver, it is referred to as a hydrophone. In seismic applications, it is referred to as a geophone.
Geophysical Applications
Published in Stephen M. Testa, Geological Aspects of Hazardous Waste Management, 2020
Seismic techniques, whether refraction or reflection, employ a seismic wave from an acoustic source and measures the subsequent travel time of seismic waves. Subsurface features can be inferred by the analysis of the travel time of the direct and refracted waves. Sources include a sledge hammer, explosives, or other method for deeper or special applications. Geophones implanted in the ground translate seismic vibrations into an electrical signal which is then displayed on the seismograph. Seismic refraction is commonly applied to investigations of up to a few hundred feet. Resolution and depth of measurements are dependent upon spacing of the geophones. Seismic reflection is effective to depths of a few thousand feet.
Tunnel construction techniques
Published in David Chapman, Nicole Metje, Alfred Stärk, Introduction to Tunnel Construction, 2017
David Chapman, Nicole Metje, Alfred Stärk
The Herrenknecht ISP method has the source and receivers placed behind the tunnel face (in contrast to the SSP system, which is positioned on the cutterhead). For gripper TBMs, the source is located on the gripper pads and the receivers are placed around the source location at approximately 10 m intervals along the tunnel. The geophone receivers are attached to anchors drilling radially into the ground. For shielded TBMs, the source is placed closer to the rear of the TBM and the receivers are placed further back, again spaced at approximately 10 m intervals along the tunnel. The geophone receivers are again attached to rods, in this case drilled through the tunnel segmental lining.
Volcano multiparameter monitoring system based on Internet of Things (IoT)
Published in Australian Journal of Electrical and Electronics Engineering, 2020
Nur Asyik Hidayatullah, Rakhmad Gusta Putra, Ardian Prima Atmaja, Dirvi Eko Juliando Sudirman, Kholis Nur Faizin, Muhamad Fajar Subkhan, Akhtar Kalam
There are four sensor nodes installed on Mount Kelud, namely nodes 1, 2, 3, and 4. Node 1 is for pH and temperature sensors, nodes 2 and 3 for CO and H2S gases sensors, and Node 4 for geophone sensor. Being mounted on the ground, nodes 2, 3, and 4 have the same mechanical design. Meanwhile, node 1 uses a buoy because it is deployed at the crater lake. The implementation of nodes 2, 3, and 4 is presented in Figure 9. The construction is made of iron pipes to support the solar panel, panel box, and sensor. All of the electronic devices are placed within the outdoors panel box for protection against corrosion. The gas sensor is placed at the outside under the protection of Stevenson screen against direct sunlight and rain. As for the geophone sensor as well as the controller board, illustration is provided in Figure 10. The geophone is positioned on the ground to detect the ground movement.
Evaluation of shear geophones in MASW testing
Published in International Journal of Geotechnical Engineering, 2019
In MASW testing, an array of equally spaced sensors (geophones) is typically used to record the ground motion as the surface waves propagate outwards from the source (Figure 1). A hammer strike is generally used to generate the waves. Typically, vertical geophones (which measure vertical component of motion) are deployed to measure the ground motion due to their wide commercial availability and lower price than shear geophones of similar frequency response. Shear geophones are becoming a viable alternative due to their capability of directly measuring shear waves in borehole-based seismic surveys and shear wave refraction. Shear geophones can be used to measure and record the horizontal component of particle motion during the propagation of surface waves (Raleigh waves). The shear geophones probably have not been tried in MASW testing for their ability in measuring the wave velocity profile of sites.
Functions and performance of sensors for slope monitoring in opencast coal mines – laboratory experimentation
Published in Petroleum Science and Technology, 2023
Sathish Kumar Mittapally, Ram Chandar Karra
Geophones are a universal tool to measure ground vibration. Thus, geophones are used to validate and calibrate the SW420 vibration sensor. Geophone consists of an electric coil and a magnetic core. When vibration occurs, the electric coil tends to be stable. The magnetic core moves along the vibration that induces an electric current, and that electrical current is calibrated by the vibration velocity (Iskander, 2018). The movement of particles while seismic waves travel through the rock are vibrations in three dimensions.