# Tagged Questions

Autocorrelation is the cross-correlation of a signal with itself.

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### matlab - detect some parts of a signal

I am trying to detect some events on this signal : This is the acceleration of someone running. By eyes we can detect many blocs, sometimes separated by a little interval. I would like to be able ...
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### Could there be any reason to prefer convolution-based calculation of autocorrelation?

Theoretically both of ways of calculating autocorrelation function are identical: strightforward convolution and Fourier-based method where we use FFT/iFFT in practice. And as it is well known, the ...
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### What does the frequency axis of a Power Spectral Density mean?

I have never really understood what the frequency axis meant when we plot the Power Spectral Density(PSD). Does it correspond to frequency as we get after we take the Fourier Transform of a time ...
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### Finding the fundamental frequency from Autocorrelated data

I'm writing an app in which I need to find the fundamental frequency of a note produced by a trombone. To do this I'm taking the FFT of audio data from a microphone and then using autocorrelation code ...
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### Where does the delta function come from if we derive autocorrelation directly?

I am reading a book "Creating Noise" written by Hollos & Hollos and have a question about the autocorrelation function of the Gaussain white noise when reading the following passage: From the ...
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### Power autocorrelation function calculation

Calculate the power autocorrelation function $\phi^p_{ff} (\tau)$ and power spectral density $\Phi^p_{ff} (\nu)$ for the signal$$f(t)=A \cos(2 \pi \nu_m t) \cos(2\pi v_c t).$$ Attempt: According to ...
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### Autocorrelation function and energy spectral density

Find the energy autocorrelation function $\phi^e_{ff}(\tau)$ and the energy spectral density $\Phi^e_{ff}(\nu)$ of the signal $f(t) = e^{-\gamma |t|},$ where $\gamma>0$ is a real constant. ...
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### Golay complementary sequences in 802.11ad

The Golay complementary sequences consist of two sequences of the same length $N$ such that there acyclic autocorrelation sequences have sidelobes equal in magnitude but opposite in sign. So, when the ...
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### Frequency autocorrelation function - Communication channel

If we have two discrete stochastic spectra and each spectra has $N$ points. We want to calculate the autocorrelation of these spectra, what should be the number of points in the resulting ...
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### Decorrelating Stationary Colored Gaussian Noise — Effect On The Desired Signal

So given stationary colored gaussian noise $\mathbf{n}$, I know that I can decorrelate it by first finding it's autocorrelation $R_{nn}$ and performing $R^{-\frac{1}{2}}_{nn} \mathbf{n}$. In ...
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### Determining the fundamental frequency/pitch of a note

What I am trying to achieve is getting the fundamental frequency of a note played by an instrument. What I have already done is performing an FFT on a samples of audio file, and here's what I get: ...
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### Evaluation of Autocorrelation and Power Spectral Density of white noise through a filter

So say there's a filter with an impulse response of $h(t) = (0.8)^t u(t)$. I'd like to pass white noise through this and figure out the autocorrelation and power spectral density of the output. I'm ...
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### Autocorrelation question

I am trying to get an understanding of autocorrelation and I am having some issues with trying to understand the process. I have a Bernoulli process called $X[t]$. In this process, $P(X[t] = 1) = p$ ...
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### Autocorrelation of a noisy linear map

I am interested in calculating the autocorrelation function of a linear map with some noise (model given below) but am slightly confused in doing so. At first, I did not realize there were two ...
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### Calculating Time Delay between initial sound and its reflection [duplicate]

I have been researching into calculating distance using sound on an iphone 6. I have been playing short frequency sweeps on one iphone and recording the data on another phone sitting on top of the ...
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### Auto correlation definition

My question has to do with the definition of auto correlation/cross-correlation for random processes. Oppenheim/Schafer (Discrete time Signal Processing, Pg. 815 (Appendix A.2),2nd ed.) define auto ...
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### Recommendation for book - Writing DSP code in C

I am looking for some good book, that simply show how you actually write a code in C, to do all the main DSP methods . DFFT Low pass and high pass filters Auto-correlation Noise processing And all ...
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### Autocorrelation of evolving channel impulse response

I have a transmission system simulated with Matlab. I send the successive symbols $S$ (vector of symbols), convolve them to the propagation channel $H$ (vector of the channel impluse response ...
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### How to implement Cross Spectral Density [duplicate]

I am writing a program to compute the cross spectral density of an image, and a template image, which is the image I am trying to find in other image. Reading wiki1,wiki2,wiki3 from wikipedia, and ...
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### The way to measure chromatic tuners' precision

I have a question about measuring precision of chromatic tuners. I want to divide 2 cases. CASE1: link; Korg AW-2G's precision If you check the link or this picture, it says that Korg AW-2G has ...
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### Getting a more accurate frequency read from autocorrelation and peak-detection algorithm

For a project I am attempting to create an automatic tuner for a guitar, which reads the audio from the guitar jack, determines the frequency and adjusts the string by a motor. Using http://www....
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### Binary Orthogonal Sequences

The set shown below is a biorthogonal signal set. $\{|0000|,|0101|,|0011|,|0110|,|1111|,|1010|,|1100|,|1001| \}$ Any two codewords or signals can be checked for orthogonality using the equation ...
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### finding the fundamental frequency in frequency domain

I want to get the fundamental frequency of a signal. I used a time domain approach first. It just sums up the differences between the signal (lets say 2048 samples) and the delayed version of the same ...
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### How do I calculate the autocorrelation of a train pulse having only the pdf?

I have a pulse train of a fixed period, but a random amplitude following a Gaussian distribution $(\mu=0,\sigma=1)$. I know how to work with a random period or delay, but how do I proceed to calculate ...