Audio Forgery Detection Based on Max Offsets for Cross Correlation between ENF and Reference Signal

2013 ◽  
pp. 253-266 ◽  
Author(s):  
Yongjian Hu ◽  
Chang-Tsun Li ◽  
Zhisheng Lv ◽  
Bei-Bei Liu
Keyword(s):  
Cross Correlation ◽  
Reference Signal ◽  
Forgery Detection

scholarly journals Feature Analysis of Degradation Signal of Rolling Stock Lateral Damper

Information ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 298
Author(s):  
Zhiyan Zhao ◽  
Bin Wu ◽  
Ting Zhou
Keyword(s):  
Cross Correlation ◽  
Wavelet Packet ◽  
Reference Signal ◽  
Correlation Method ◽  
Health Condition ◽  
Wavelet Packet Transform ◽  
Rolling Stock ◽  
Health State ◽  
Vibration Signals ◽  
Cross Correlation Analysis

The lateral damper is one of the key components of rolling stock. Establishing the relationship between the degraded signal and the health state of the lateral damper is important in order to perform timely performance detection and fault diagnosis. This paper proposes a wavelet packet cross-correlation method (WPCC) that is based on wavelet packet transform (WPT) and cross-correlation analysis (CCA). First, the vibration signals under different running speeds, different running conditions, and different track excitations were collected and analyzed. Second, the wavelet packet transform was used to select larger energy band signals for reconstruction. Subsequently, the WPCC coefficient was calculated between the reference signal and the signal to be measured. The proposed method was applied to analysis of vibration signals of the lateral damper performance degradation. The lateral damper health condition was divided into four intervals, and the average accuracy calculated under different running speeds, different running conditions, and different track excitation was 95%.

scholarly journals Application of Phase-Only Correlation to Travel-Time Determination in GNSS-Acoustic Positioning

2021 ◽  
Vol 9 ◽  
Author(s):  
Chie Honsho ◽  
Motoyuki Kido ◽  
Toshihito Ichikawa ◽  
Toru Ohashi ◽  
Taichi Kawakami ◽  
...  
Keyword(s):  
Travel Time ◽  
Template Matching ◽  
Cross Correlation ◽  
Incident Angle ◽  
Reference Signal ◽  
Phase Changes ◽  
Main Peak ◽  
Auto Correlation ◽  
Acoustic Ranging ◽  
Short Period

The GNSS-acoustic technique is a geodetic method for oceanic areas that combines GNSS positioning of a sea-surface platform and acoustic ranging of seafloor stations. Its positioning accuracy is typically a few and several centimeters for the horizontal and vertical positions, respectively. For further accuracy enhancement, we examined the errors in travel time, the most fundamental data in acoustic ranging. The reference signal used in our observations is a series of sinusoidal waves modulated by binary phase-shift keying with a maximal length sequence whose auto-correlation has a clear main peak at zero lag. However, cross-correlation between the actual returned signal and reference signal is often accompanied by many large sidelobes and looks very different from the synthetic auto-correlation. As a practical measure, we have chosen empirically one peak among several comparable peaks in the cross-correlation, though that is likely to lead to systematic errors in travel time. In this study, we revealed that a variety of cross-correlation waveform primarily depends on the incident angle of acoustic paths and that sidelobes were significantly reduced by substituting phase-only correlation (POC) for conventional cross-correlation. We therefore developed a template-matching technique using POC for the peak detection. POC templates were prepared by stacking actual POCs with certain ranges of the incident angle for each campaign. In the application of this method to actual data, we achieved successful results of our numerous campaign data to date. We consider that POC is advantageous in identifying the main peak uniquely and performing template matching more robustly, because POC enhances short-period components and thus highlights the timing of phase changes further than conventional cross-correlation.

Retrieving the Reflection events from passive signals

2020 ◽  
Author(s):  
Diako Hariri Naghadeh ◽  
Chris Bean
Keyword(s):  
Cross Correlation ◽  
Reference Signal ◽  
The Body ◽  
Body Waves ◽  
Estimation Methods ◽  
Wave Inversion ◽  
Correlation Processing ◽  
Processing Module ◽  
Ground Roll ◽  
Coherence Spectrum

<p>To create virtual shot gather from passive signals it is essential to cross-correlate all the signals with the reference trace. Since surface sources dominate the origin of seismic noise, the correlated sections are highly dominated by surface waves. If the target is surface wave inversion general cross-correlation will suit the target. But if the extraction of body waves from those signals is the main objective, coherent ground roll events mask the body waves making it difficult to extract them. To tackle this issue a frequency-spatial nonCoherent filter (FX-NCF) plus a post-correlation processing module are introduced. FX-NCF is a prediction filter and the filter operator is a function of frequency, station interval and the slope of the interested event. In the frequency domain, the filter is looking for the prediction of n-th trace coherence spectrum from the (n-1)-th signal’s coherence spectrum by minimizing the objective function. Hybrid norms used to minimize the error. The coherence spectrum of each trace is the coherency between the reference signal and the desired trace. Applying the FX-NCF on 2D real recorded passive signals shows its superiority over general cross-correlation, deconvolution interferometry, cross-coherence and multi-taper-method-coherence-estimation methods in highlighting surface and body waves also improving the signal-to-noise (S/N) ratio. To show the necessity of post correlation processing (before applying on real recorded signals) to highlight reflection events, hyperbolic Radon transform (HRT) as a suitable post-correlation module applied on correlated section due to applied FX-NCF on simulated passive signals from a simple 2D synthetic model. The result encouraged us to apply the same hybrid modules (FX-NCF plus HRT) on real recorded passive signals to reconstruct wanted reflection events.</p>

Nondestructive Testing Method in Artificial Intelligence Real Time Systems

2004 ◽  
Vol 97-98 ◽  
pp. 71-76
Author(s):  
Egidijus Kazanavicius ◽  
Antanas Mikuckas ◽  
Irena Mikuckiene
Keyword(s):  
Signal Processing ◽  
Correlation Function ◽  
Nondestructive Testing ◽  
Cross Correlation ◽  
Reduction Method ◽  
Reference Signal ◽  
Floating Point ◽  
Real Time Systems ◽  
Reflected Signal ◽  
Time Systems

Modern sonar and radar measurement systems are widely used in the field of nondestructive testing for a long time. Usually reference signal is emitted towards the object to be investigated and we get a signal, which is the sum of reference signal reflected from different plies. The task of signal processing is to determine time instances corresponding positions of certain ply, which allow analyzing structure of object. Usually the cross correlation function (CCF) of transmitted sequence and received sequence is calculated. If peaks were clearly identified in the cross correlation function (CCF), it would be easy to determine time instances. Due to the noise some coherent peaks, additive to the expected peaks, appear on the CCF, which are confusing in regard to the clear distinction of target. In order to cancel effects of noise as much as possible some measures have to be taken for data manipulation noise cancellation, such as averaging, inverse filtering and so on. These signal-processing methods need a lot of floating point floating point operations and are time consuming. That is why the usage of such ultrasonic systems is limited in real time systems, which are the base for self-organizing systems. Amount of calculations depends on the length of reference signal, the length of reflected signal to be processed and the noise reduction method used in such system. A new system with reduced amount of calculations is considered in this article. In this system only parts of reflected signal corresponding peaks of CCF are processed. These parts are defined in acquisition mode and afterwards system enters measurement mode. New noise reduction method based on wavelet transforms coefficients thresholding is applied in this system. The length of reference signal impacts system noise immunity and amount of calculations. The main problem in ultrasonic non-destructive testing systems is to cancel out effects of the noise. The optimal length of reference signal for wavelet based signalprocessing method is defined. All these measures allowed significantly reduce amount of calculations in the self-organizing systems.

Correlation in real time

1966 ◽  
Vol 290 (1422) ◽  
pp. 430-447 ◽  
Keyword(s):  
Correlation Function ◽  
Real Time ◽  
Cross Correlation ◽  
Reference Signal ◽  
Cross Correlation Function ◽  
Time Compression ◽  
Time Operation ◽  
Real Time Operation ◽  
The Cross ◽  
Conventional Manner

The process of correlation can be effected in real time only by methods of time compression, or by replacement of the fundamental integration over time by an integration over distance. The Deltic correlator is an example of the first, while optical correlators and tapped delay line matched filters illustrate the second; the paper summarizes these techniques. Two new forms of real-time correlator are described. The first provides correlation of an incoming waveform against a reference waveform which is known in advance. The reference signal is stored in the device as a thin copper waveform made, for ease and economy, by a standard printed circuit process. A magnetic tape passes over and along this waveform, and the input signal is recorded on this tape in the conventional manner. The output from the copper waveform, after equalization, is the cross correlation function of the two waveforms. The second form of correlator provides real-time operation where neither signal is known in advance. Both in put signals are recorded in duplicate on magnetic tapes. From these tapes magnetic fields representing the sum and difference of the two waveforms are derived, and these fields are used to energize two extended magnetoresistive elements. These operate in the manner of a quarter-squares multiplier to produce a change of resistance which follows the cross correlation function of the two waveforms. Both correlators can be realized in several configurations adapted to particular needs within and outside of seismology.

scholarly journals A High-Resolution Ultrasonic Ranging System Using Laser Sensing and a Cross-Correlation Method

2019 ◽  
Vol 9 (7) ◽  
pp. 1483 ◽  
Author(s):  
Lecheng Jia ◽  
Bin Xue ◽  
Shili Chen ◽  
Hanzhong Wu ◽  
Xiaoxia Yang ◽  
...  
Keyword(s):  
High Resolution ◽  
Sound Velocity ◽  
Cross Correlation ◽  
Reference Signal ◽  
Correlation Method ◽  
Repeatability Error ◽  
Laser Sensing ◽  
Measurement Resolution ◽  
Ultrasonic Ranging ◽  
Potential Applications

Ultrasound has been proven to be a valid tool for ranging, especially in water. In this paper, we design a high-resolution ultrasonic ranging system that uses a thin laser beam as an ultrasonic sensor. The laser sensing provides a noncontact method for ultrasound detection based on acousto-optic diffraction. Unlike conventional methods, the ultrasound transmitted from the transducer is recorded as the reference signal when it first passes through the laser. It can be used to improve the accuracy and resolution of the time-of-flight (TOF) by a cross-correlation method. Transducers with a central frequency of 1 MHz and diameters of 20 mm and 28 mm are used in the experiment. Five targets and a test piece are used to evaluate the ranging performance. The sound velocity is measured by the sound velocity profiler (SVP). The repeatability error of TOF is less than 4 ns, and the theoretical resolution of TOF is 0.4 ns. The results show a measurement resolution within one-tenth of the wavelength of ultrasound and an accuracy better than 0.3 mm for targets at a distance up to 0.8 m. The proposed system has potential applications in underwater ranging and thickness detection.

scholarly journals Efficient Detection of Multiple FBG Wavelength Peaks using Matched Filtering Technique

2021 ◽  
Author(s):  
Sunil Kumar
Keyword(s):  
Cross Correlation ◽  
Reference Signal ◽  
Peak Detection ◽  
Matched Filtering ◽  
Peak Wavelength ◽  
Zero Crossing ◽  
Efficient Detection ◽  
Spectral Signal ◽  
Filtering Technique ◽  
The Cross

Abstract We propose an efficient technique for FBG peak detection based on matched filtering technique. The matched filtering process is based on resonance point estimation between a standard reference spectral signal and a reflected spectrum of FBG. The desired peak wavelength and corresponding peak intensity are predicted by determining of the cross-correlation between the FBG signal and 3rd derivative of the reference signal. The peak wavelength and intensity are found from the zero-crossing points of the cross-correlation function. The Mexican-hat wavelet function is chosen as the reference spectral signal due to its narrow shape. The proposed algorithm can suitably be used for multiple peak detection when several FBGs are cascaded and if the FBG signal is weak and noisy.

scholarly journals ENF Based Video Forgery Detection Algorithm

2020 ◽  
Vol 12 (1) ◽  
pp. 131-156
Author(s):  
Yufei Wang ◽  
Yongjian Hu ◽  
Alan Wee-Chung Liew ◽  
Chang-Tsun Li
Keyword(s):  
Spline Interpolation ◽  
Reference Signal ◽  
Detection Algorithm ◽  
Frame Rate ◽  
Forgery Detection ◽  
Video Forgery Detection ◽  
Data Points ◽  
Exact Position ◽  
Video Forgery ◽  
Low Frame Rate

The electric network frequency (ENF) is recorded in the videos taken under the lights powered by grid and can be used for digital forensics. However, due to the lack of data caused by the low frame rate of the video, the ENF-based forensics methods always need a reference signal extracted from the grid, which limits the practical application of these methods. In this article, a new ENF-based time domain video forgery detection algorithm is proposed to solve the problem of data lack. The cubic spline interpolation is used to generate suitable data points of the ENF signal, and the detection sequence generated based on the correlation coefficient between data points in adjacent periods is used to catch the phase continuity interruption of the ENF signal and detect the exact position of forgery. The proposed algorithm can be used independently without any reference signals. The experimental results show that the proposed algorithm has good performance in detecting forgery videos with varying degrees of deletion, duplication and insertion of frames.

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