American Journal of Earth Science and Engineering  
Manuscript Information
 
 
Geophones for Recording Acoustic Waves in Water
American Journal of Earth Science and Engineering
Vol.1 , No. 3, Publication Date: Jun. 8, 2018, Page: 166-173
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Authors
 
[1]    

Askold Belyakov, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russia.

 
Abstract
 

In the modern concept, the geophone is an electrodynamic converter. The geophone has a mechanical resonance at frequency f0. In practice, a characteristic area is used after resonance with a linear frequency dependence (f1) limited to a frequency of 110-120 Hz. The amplitude-frequency characteristic of a piezoelectric transducer has a quadratic dependence of the amplitude on the frequency (f2). But the disadvantage of the piezoelectric transducer is its high impedance, which requires the mandatory use of a preamplifier with a high input impedance. The current requirements for increasing the resolution of seismic exploration of oil and gas by amplitude and frequency have served as a pretext for developing a new geophone converter similar to an electrodynamic geophone, but which uses a section before mechanical resonance with a cubic amplitude-frequency dependence (f3) as the performance characteristic. This allowed solving the problems inherent in traditional geophones, namely: expand the range of recorded frequencies from 1 to 1000 Hz, increasing the upper limit of the frequency of received signals to 1 (5) kHz. In parentheses, the calculated data for the fifth generation geophone are given. The new transducer was developed on the basis of the magnetoelastic effect in a ferromagnet with a crystalline structure (iron-aluminum alloy), which allowed the construction of a vector sensor with a single inertial mass and three electric windings. Modern hydrophones use mainly piezoelectric effects of crystalline and ceramic materials with high sensitivity to pressure. But the large output impedance of the piezoelectric transducer requires a special preamplifier with a high input impedance. The hydrophone, unlike a geophone with an inert mass, is a scalar device. To determine the direction of arrival of the acoustic signal, and this is one of the main tasks of the device, it is necessary to create special antennas of large dimensions. With the use of a new transducer, a hydrophone with an inertial system can be constructed that will measure three components of the wave velocity vector (pressure gradient) of the acoustic wave in water.


Keywords
 

Geophone, Hydrophone, Scalar Measurement, Vector Measurement, High Resolution, Vibrating Speed, Gradient Pressure


Reference
 
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