FFT, hydrophone array, Signal Processing technique for removing ocean reverberation and incoherent noise

1978 ◽  
Vol 63 (S1) ◽  
pp. S48-S49
Author(s):  
Jont B. Allen
Keyword(s):  
Signal Processing ◽  
Array Signal Processing ◽  
Processing Technique ◽  
Signal Processing Technique ◽  
Hydrophone Array ◽  
Incoherent Noise

A multiple filtering and correlation array signal processing technique for cased-hole acoustic logging and applications

2020 ◽  
Vol 8 (3) ◽  
pp. SL1-SL8
Author(s):  
Fan-Tong Kong ◽  
Can Jiang ◽  
Yuan-Da Su ◽  
Xiao-Ming Tang
Keyword(s):  
Signal Processing ◽  
Wave Velocity ◽  
Array Signal Processing ◽  
Processing Technique ◽  
Processing Method ◽  
S Wave ◽  
Signal Processing Technique ◽  
Acoustic Logging ◽  
Waveform Data ◽  
Low Coherence

In cased-hole acoustic logging, estimating the formation velocity is often problematic when the casing is poorly bonded with the formation. The overwhelmingly large casing waves dominate the measured waveforms and overlap with the low-coherence, weak formation arrival, contributing to the failure of conventional semblance processing method. To tackle this problem, we have developed a filtered frequency semblance array waveform signal processing technique. The multiple filter technique is first used to filter the measured waveforms. We then apply the [Formula: see text]th root stacking method to the filtered signals. Consequently, the coherence of the formation signal on the obtained 3D semblance correlogram is significantly enhanced and clearly separated with the casing waves. We have applied the method to process synthetic and field cased-hole acoustic waveform data. Our results indicate that the new method significantly enhances the coherence of the desired formation signal and simultaneously estimates the formation of the P- and S-wave velocity.

scholarly journals A Remote Sensor System Based on TDLAS Technique for Ammonia Leakage Monitoring

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2448
Author(s):  
Hongbin Lu ◽  
Chuantao Zheng ◽  
Lei Zhang ◽  
Zhiwei Liu ◽  
Fang Song ◽  
...  
Keyword(s):  
Signal Processing ◽  
Limit Of Detection ◽  
Processing Technique ◽  
Tunable Diode Laser ◽  
Sensor System ◽  
Signal Processing Technique ◽  
Suppression Effect ◽  
Output Wavelength ◽  
Deviation Analysis ◽  
Remote Sensor

The development of an efficient, portable, real-time, and high-precision ammonia (NH3) remote sensor system is of great significance for environmental protection and citizens’ health. We developed a NH3 remote sensor system based on tunable diode laser absorption spectroscopy (TDLAS) technique to measure the NH3 leakage. In order to eliminate the interference of water vapor on NH3 detection, the wavelength-locked wavelength modulation spectroscopy technique was adopted to stabilize the output wavelength of the laser at 6612.7 cm−1, which significantly increased the sampling frequency of the sensor system. To solve the problem in that the light intensity received by the detector keeps changing, the 2f/1f signal processing technique was adopted. The practical application results proved that the 2f/1f signal processing technique had a satisfactory suppression effect on the signal fluctuation caused by distance changing. Using Allan deviation analysis, we determined the stability and limit of detection (LoD). The system could reach a LoD of 16.6 ppm·m at an average time of 2.8 s, and a LoD of 0.5 ppm·m at an optimum averaging time of 778.4 s. Finally, the measurement result of simulated ammonia leakage verified that the ammonia remote sensor system could meet the need for ammonia leakage detection in the industrial production process.

scholarly journals Application of UAV in Search and Rescue Actions in Underground Mine—A Specific Sound Detection in Noisy Acoustic Signal

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3725
Author(s):  
Paweł Zimroz ◽  
Paweł Trybała ◽  
Adam Wróblewski ◽  
Mateusz Góralczyk ◽  
Jarosław Szrek ◽  
...  
Keyword(s):  
Signal Processing ◽  
Acoustic Signal ◽  
Processing Technique ◽  
Underground Mine ◽  
Search And Rescue ◽  
Reference Spectrum ◽  
Signal Processing Technique ◽  
Time Frequency ◽  
Communication Device ◽  
Frequency Representation

The possibility of the application of an unmanned aerial vehicle (UAV) in search and rescue activities in a deep underground mine has been investigated. In the presented case study, a UAV is searching for a lost or injured human who is able to call for help but is not able to move or use any communication device. A UAV capturing acoustic data while flying through underground corridors is used. The acoustic signal is very noisy since during the flight the UAV contributes high-energetic emission. The main goal of the paper is to present an automatic signal processing procedure for detection of a specific sound (supposed to contain voice activity) in presence of heavy, time-varying noise from UAV. The proposed acoustic signal processing technique is based on time-frequency representation and Euclidean distance measurement between reference spectrum (UAV noise only) and captured data. As both the UAV and “injured” person were equipped with synchronized microphones during the experiment, validation has been performed. Two experiments carried out in lab conditions, as well as one in an underground mine, provided very satisfactory results.

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