# Questions tagged [cross-correlation]

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1answer
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### Cross-correlation of two signals using matlab

I am trying to measure the similarity between two signals and I am using cross-correlation to achieve this. Following the matlab example, I seem to have accomplished that, however, I do not ...
1answer
6k views

### How to normalize output of $\tt scipy.signal.correlate$

I have 2 different signals and I'm trying to cross-correlate then using Python 2.7 and scipy.signal.correlate. How do I normalize my results (such that the max ...
1answer
2k views

### xcorr in MATLAB for periodic function

I have a periodic signal and I want to find it's autocorrelation function. I can calculate it exactly: $$R_{uu}(h) = \frac 1M \sum_{k=0}^{M-1} u(k)\cdot u(k-h)$$ But will ...
3answers
230 views

### How do I know quantitatively if the correlation of two time series is significant?

I computed the correlation coefficient of two time series of daily observations, x and y, but noticed that the more sampling ...
1answer
890 views

### Is Cross correlation between stationary random signal and noise zero for all lags?

If $x(n)$ is a stationary random process (let say small 20ms window of speech which can be assumed stationary) and $v(n)$ is said to be uncorrelated noise, can we say that cross correlation of $x(n)$ ...
1answer
108 views

### How to find the time instant where my sent signal and received signal can synchronize?

I am having two .wav files, one is modulated wave that is made into a .wav file and another is a recieved .wav file which is recorded from microphone while playing first modulated .wav file. So now ...
2answers
58 views

### How to discover an image clone

I have an image depicting a results of gel electrophoresis (it does not really matter - it just means: no bodies, faces, predictible objects) and I have a strong suspicion that a part of the image ...
1answer
402 views

### Code generation for sum function in MATLAB

In cross correlation we use the below command to calculate the sum after elementary multiplication of the vectors. But when we try to convert this Matlab code to vhdl using HDL coder, this command is ...
1answer
227 views

### Mismatched offset when computing cross-correlation using FFT

In MATLAB if I compute the cross-correlation of 2 arbitrary signals using the xcorr function I get exactly the answer I expect. If I then calculate the cross-correlation using element-wise fft ...
2answers
1k views

### How to Match 2 Signals which Are a Shifted and Scaled Version of Each Other

I have 2 signals S1 and S2 that contain the same information, but S2 is shifted and scaled compared to S1 by an unknown amount (but small; eg shift would be of the order of 1-10 samples). What is the ...
2answers
2k views

### Difference Between Correlation / Convolution and Matrix Multiplication

Can anyone please clarify the difference between correlation/convolution and matrix multiplication? As I thought either convolution or correlation is similar to matrix multiplication. I read this ...
1answer
745 views

### Time delay estimation using ultrasound

I have a sound source that generates an ultrasonic pulse. I have two microphones seperated by a distance which are at a distance from the source. I want to find the time delay of arrival of the ...
1answer
4k views

### Finding periodicity of spikes, matlab

In my time series data, I have often spikes with regular periods. Sometimes, I get two or three different periodical spike sequences (two electrical noise sources), some with T1 seconds period, some ...
1answer
53 views

### RF-Chain Signal Delay for Sensor Switching

Lets have a RF-chain as above with system bandwith from HP corner to the green line say 1 MHz. The signal accumulates delay as it passes through this analog chain, and due to it being non-liner filter ...
1answer
26 views

### How does a correlation receiver ensure which transmitted data does a user see?

Hello! I understand that using correlation, one can set up a system wherein multiple users can transmit at the same time using the same channel. And theoretically, I understand that if the correlation ...
1answer
70 views

### Real Data Complex Transfer Function using H0, H1, H2 Estimators

BACKGROUND: This question is attempting to consolidate material discussed in two previous topics. These are: Understanding the H1 and H2 estimators @Pontus S Frequency-domain deconvolution: "...
1answer
49 views

### Is there any way to align temporally two signals in spectrogram?

I am keen to know that If I have two signals say : Farend_signal (y[n]) and Nearend_signal (x[n]) and x[n] also contains an echo of y[n] with some delay. Is there any technique to align these two ...
1answer
32 views

### Finding delay where squared error between signal and data is minimal

I have a set of points which correspond to part of a known signal. What I want to do is estimate the delay between the set of points and the known signal. In this case, I don't think cross ...
1answer
190 views

### Proving the upper bound of cross correlation

I am reading about cross-correlation from this document and equation (5) states that The maximum value of the crosscorrelation is not always when the shift equals zero; however, we can prove the ...
1answer
62 views

### Convolution and Cross Correlation Blackbox

Suppose I was handed a blackbox that I know is either a Convolution filter or Cross-Correlation filter, and my job is to find out which it is. My idea is to pretend that it's Cross-Correlation and ...
1answer
46 views

3answers
1k views

### Downsampling from 100Hz to 60 Hz

I have two sensors measuring a single time varying signal . The first sensor (reference sensor) is sampling the data at 60 Hz and the second sensor (test sensor) is sampling the data at 60 Hz. I ...
1answer
665 views

### DoA estimation using microphone array

I am using an array of 4 microphones in a square formation. My goal is to estimate the direction (azimuth only) of incoming speech sound. The array looks like this: I have recordings from the array ...
1answer
293 views

### find cross correlation lag by optimization

I have data from many closely located sensors (geophones). These are often contaminated with coherent noise which I need to remove. Some of the most effective de-noising methodologies work if the ...
2answers
698 views

### Audio template matching - power correlation?

I'm looking at some code that matches audio templates in a longer audio file. The calculation correlates the power spectra of the template and audio file, maximizing over the possible alignments. This ...
1answer
432 views

### Scaling Data before Fourier transform

I am doing an experiment, where I am trying to get the same results from correlating two matrices in the fourier domain and then scaling the data by some constant. Method_1: Do FFT, Correlate the ...
2answers
1k views

### Cross correlation peak value

I would like to measure the time delay between two signals. By applying the cross correlation I get the time delay or number of samples by the location of the cross correlation peak, however I am ...
2answers
588 views

### Range and motion in received signals by radar

I've got two signals which are consecutive received signals by a radar system. The signals' values are complex (in form $x+\textrm iy$). I have generated a trasmitted signal using the info available. ...
1answer
49 views

### How to decode speaker gender from spoken transcript

I have 20 audio recordings (raw format) of people reciting the same ~50 word transcript. I would like to use audio signal analysis to decode speaker gender from audio recording. Intuitively, it ...
1answer
221 views

### Fast cross correlation with limited range

I am measuring the phase shift between two pseudorandom signals using correlation ifft(A.conjugate()*B) and picking out the maximum). That works very well, but takes a lot of time. I roughly know ...
1answer
613 views

### Detecting a frequency pattern in the frequency domain

I am looking to detect a combination of frequencies in the frequency domain. For example, here is my spectrum: And I'm trying to detect the pilot tone. I have the FFT of the pilot tone: which zoomed ...
1answer
3k views

### Signal compare - cross corelation in frequency domain matlab

I need compare two signals. Signals have simliar shapes but completely different values (as on picture): So I think cross corelation in frequency domain should gave me a number that shows me how the ...
1answer
4k views

### How can I compute a time-frequency cross-spectrum in MATLAB?

MATLAB has a spectrogram function for the time-frequency analysis of a single signal. It also has a cpsd function for estimating the cross-frequency spectrum for two signals. However, cpsd averages ...
1answer
666 views

### Calculating an impulse response in a stable environment

I would like to estimate the impulse response of a simple environment (room, two speakers, one microphone). I am aware of the issues/limitations of working with "near" LTI systems. That said, I have a ...
2answers
264 views

### Correlation between 2 functions

I have a periodical function $f(x)$ that is sampled in time, at a rate of 1 millisecond. Together with this, I also have a second function $t(x)$. I want to find the correlations between periods ...
1answer
39 views

### Comparing spectrogram similarity over time

I have a data set of spectrograms from moving audio recorders. As the recorders get closer, I expect the spectrograms to become more "similar". I expect this "similarity" to be a ...
1answer
35 views

### Map time/scene differences between two similar videos

Goal: Given two videos that are episodes from series but in different format (one Bluray/one TV for example), map the time differences between the two (which scenes are not in one of the two) and be ...
0answers
36 views

### Is it possible to normalize an un-normalized cross-correlation vector after computation

I have a C++ code that computes cross-correlation for a given 2 vectors as input. It doesn't have an implicit normalization or normalized implementation of cross-correlation. But I would prefer a ...
1answer
198 views

### CWT at low scales: PyWavelets vs Scipy

Low scales are arguably the most challenging to implement due to limitations in discretized representations. Detailed comparison here; the principal difference is in how the two handle wavelets at ...
1answer
156 views

### Fourier Transforms, Convolution, Cross-correlation: what is their physical unit exactly?

Let us assume we are talking about real, deterministic, electrical signals $x(t)$ and $y(t)$ (magnitude in Volts). There are different kind of Fourier Transforms. I made a table to summarize: NB: By ...
1answer
120 views

### GCC-PHAT always peaks at zero when estimating delay offset

My question is that when I used gcc-phat to estimate delay between two audio signals, it always returns zero offset. However normal cross correlation Xcorr gives a good result. I don't know the reason....
2answers
59 views

### Comparing similarity of two simultaneously recorded EEGs in freq domain

I have two EEG signals that are simultaneously recorded during the night (sleep). Imagine one device recorded from channel F4 and the other from Fp2. Now I would like to check the similarity of these ...
0answers
39 views

### Instantaneous frequency, PLLs, frequency mixing, cross-correlation and the cross-correlation matrix

This is as much a request for comment and critique as anything else. I am looking at tracking how a system perturbs an input that is a (real) sinoid of varying frequency. ...
0answers
28 views

### Increasing samples per symbol degrades correlation between signals

I am trying to implement a simple pseudo-noise (PN) ranging simulation. I have used this GNU Radio example, and I have adapted it a bit to suit my needs. Here is a screenshot of my flowchart: The ...
1answer
33 views

### Variance of circular vector correlation

Say I have two zero-mean vectors, with a size of N and the translation between them is k. Say the image signal std is $\sigma_s$ and the noise std is given by $\sigma_n$. What is the variance of the ...
0answers
53 views

### How to extract information about each constituent 'wave' of a signal?

I have a vector containing wind speeds sampled at 1Hz over ten minutes. I have applied a lowpass filter of 0.25Hz to get only the wind speeds I am interested in. I now want to use MATLAB to ...
0answers
36 views

### Pearson correlation coefficient vs mutual information

I recently computed both the pearson coefficient and the mutual information of two time series as well as the corresponding error bars, and what I find out in the end is a significant level of ...
1answer
61 views

### Phase lag changes cross spectrum

I have a same noise passing through two different ARMA filter. The autospectrum of first filter is given by S11=G1*G1*S_in where S_in is input spectrum created by set of random numbers. Similarly the ...