# Tagged Questions

Digital signal processing of sound, video or other single or multidimensional data

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### Power spectrum density calulation with ARProcess

I have a measurement of $x$ coordinates of an oscillating particle at presence of noise taken at constant time steps of 1/60 s. The corresponding data set can be obtained here: http://goo.gl/...
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### What does ℜn mean? [migrated]

I came across the symbol ℜ in the Kalman introduction: http://www.cs.unc.edu/~welch/media/pdf/kalman_intro.pdf x∈ℜm It was used in this context: ...
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### Why isn't LowPassFilter working for these parameters?

First I define a function, just a sum of a few sin waves at different angular frequencies: ...
106 views

### Identify a note in a song using Mathematica

I'm trying to figure out how to use Mathematica to identify a note from a song. The short .mp3 file found here or here contains a bass-note that I'd like to identify. I can find it through ...
87 views

### Filtering in frequency domain

I'm trying to modify a transfer function in the frequency domain by filtering it with a Butterworth filter. For example, let's say my transfer function is of the form : ...
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### Applying a window over a list

The window functions state that they tread over lists, but when I try to do: HammingWindow/@list, I do not get the expected results. What is the best way to apply a window over an arbitrary length ...
47 views

### FindPeaks error “ Expecting an image or graphics instead of”

I'm running Mathematica 10.3.1.0 on windows 7 Professional Sp.1 when I try to use FindPeaks I keep getting the following error, even when trying the example in the ...
82 views

### Problem with Sin and ListPlot

In order to produce a smooth sine wave (Sin) and visualize it (ListPlot), I seem to need a very high sample rate (much higher than Nyquist). I want to know if this is a artifact of ListPlot or Sin ...
106 views

### Plotting amplitude spectra of modulated message signal

I'm trying to plot the amplitude spectrum of the modulated message signal, I have managed to plot it by working through the maths, expanding out each trig function, and then drawing onto a graph ...
64 views

### Why there is a click sound when I play a sound?

When I consider this simple code: ListPlay[RandomReal[1, {2000}], SampleRate -> 1000] I hear a click at the beginning of the sound sample and at the end of ...
76 views

### Mapping the MATLAB SP Toolbox to Mathematica

We have some work and people where I am doing signal processing using the signal processing toolbox in MATLAB and it comes up how to translate one or another of the large number of functions in that ...
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### Wavelet Data Visualization (modus and phase) ListPlot [closed]

Due to ContinuousWaveletTransform[...] I can obtain information about wavelet-coefficient for example ...
111 views

### Getting correct amplitudes with Periodogram

I'm having some trouble with the function Periodogram, mainly with getting it to produce correct amplitudes for the spectrum it returns. My question is how to fix ...
86 views

### Is oscillation seen in data signal or noise? [closed]

I have some experimental data which is well-fitted by 40 terms of a Fourier series. I want to know if the oscillation exhibited is signal or noise. I evaluated the code shown below to plot my data in ...
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### Engineering spectral densities using filtered white noise

My goal is to create time-spectrum noise signals with spectral densities $S_{xx}(f)$ for pretty much arbitrary spectral densities (think white noise, lorentzian, $1/f$). In finding advice on how to do ...
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### Constructing the spectral density of white noise

My goal is to find the spectral density $S_{XX}(f)$ from a time domain noise signal $X(t)$. The approach should work for general time series, but to illustrate what I've been doing I'll keep it simple:...
214 views

### Extracting signal from gaussian noise

I am trying to extract a signal, $X$, from a noisy source of data, $Z$: $Z = X + Y$ where I know that $Y\sim N(0,\sigma)$, and I know the standard deviation $\sigma$. I am starting with a surrogate ...
270 views

### Using BandpassFilter

https://drive.google.com/file/d/0B7G3oUuZG1TwRHNNV1RFZjFWUXM/view?usp=sharing Above I have linked a data set containing a 2 seconds EEG sample I have recorded of someone "blinking". This data set was ...
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### How can I convert a Sound created with SoundNote to a list of samples?

I have a Sound created with SoundNote, as follows: simpleSound = Sound[SoundNote["C"]] ...
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### Absurd solution by LinearSolve

I am trying to find curve that passes through all the data points.To do this i am doing interpolation using LinearSolve. No. of equations vary from 1000 to 3000. LinearSolve gives me values of ...
84 views

### Application of lowpass Butterworth filter

I'm trying to design a Butterworth lowpass filter with a cutoff frequency of So far what I did is ...
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### Mathematica nested loops [closed]

I can write down the following Python code: for j1 > 2: time1 = i1 for i2 > i1: if j2 < 2: time2 = i2 break Purpose of the above code: ...
219 views

### Estimating Power Spectral Density from Autocorrelation

I have been tasked with computing the power spectrum of a noisy signal. Specifically, I am asked to do so through first attaining the autocorrelation function. From what I have read, the PSD is simply ...
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### 1D phase unwrapping [duplicate]

I want to unwrap a signal but I don't know where to add the 2 Pi. How should I unwrap the phase? ...
415 views

### How to compute the Power Spectral Density of an EEG signal [closed]

I have an EEG signal of length N on a given channel (FP1). I would like to compute the power spectral density of the signal. More specifically, once the PSD is computed, I would like to sum the ...
86 views

### How does KalmanEstimator update the Kalman gain, process noise and state variable mean?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity. ...
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### We need to know the input signal when we use KalmanEstimator?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity. ...
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### What does OutputResponse[sys, { {u1,u2,u3}, {v1,v2,v3} } ] do?

I am puzzled by the result of OutputResponse[sys, {{u1,u2,u3},{v1,v2,v3}}]. OutputResponse is used this way in the first "Application" in the documentation for <...
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### What are all the elements of the expression returned by KalmanEstimator used for?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity. ...
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### Why the BandpassFilter is different than applying LowpassFilter then HighpassFilter

If I generate some data with noise, and use a filter to filter the noise, why does BandpassFilter not produce the same results as using ...
367 views

### How to make sense of LowpassFilter, SampleRate and the cutoff frequency ωc in different Mathematica versions?

How do you make sense of the scale of "time" and "sampling" when using LowpassFilter and SampleRate ? Given the test data with ...
426 views

### How to extract notes and chords from audio?

I have a 3-second recording of a guitar chord which you can safely download here. I'm trying to use Mathematica's wavelet features to find out the notes in the chord, at least the docs says that ...
190 views

### Nonuniform Savitzky-Golay filter for smoothing and differentiation

The classical Savitzky-Golay filter works only with uniformly sampled data and currently we have at least two good implementations of it for Mathematica published on our site. But in many practical ...
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### How to find the starting point of an oscillation (with noise)?

I've got a series of coordinates which start to oscillate from some time (and with noise), like this: ...
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### Are there any open source projects related to signal processing

I am going to make a program related to audio signal processing . Are there any open source projects related to it?
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### PeriodogramArray or PowerSpectralDensity?

could anyone explain what is the difference between PowerSpectralDensity[data,omega] and PeriodogramArray[data]? When I plot them (starting from the same set of data of course) I get two different ...
745 views

### Cross-Correlation with TimeSeries

How to find hidden relationship between two TimeSeries data sets? I normally compute the Cross-Correlation function, but I cannot find an easy way of doing this on the TimeSeries objects in ...
238 views

### Extracting out the Fourier modes of a series, and using these to reconstruct data series

I would like to extract the most important frequency modes from a data set which exhibits strong annual periodicity, as well as some (less) important shorter-term frequency components. The following ...
503 views

### Wavelet Transform Modulus Maxima (WTMM) method

Has anyone already coded the Wavelet Transform Modulus Maxima (WTMM) method for computing the singular spectrum using multi fractal formalism in Mathematica? The goal is to analyse 1D, 2D and 3D data....