Questions tagged [signal-processing]
Digital signal processing of sound, video or other single or multidimensional data
251 questions
46
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4
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Implementing continuous phase/Arg function
In MATLAB there's a function called phase that is just like our Listable friend Arg, but ...
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41
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3
answers
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What's the correct way to shift zero frequency to the center of a Fourier Transform?
I'm trying to apply a Fourier transform of a one dimensional list of a time history of some quantity using the Fourier function. I'm interested in the frequency ...
- 27.8k
40
votes
3
answers
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Remove noise from data
Hi, as you can see above I have some experimental data which has a large offset and shows clear noise fluctations around the tendency of the curve. I wanted to ask if someone could suggest me a method ...
- 543
32
votes
4
answers
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Implementing discrete and continuous Hilbert transforms
What is an efficient and accurate Mathematica implementation of the Hilbert transform, for both continuous and especially discretely sampled functions?
This transform relates phase and amplitude in ...
- 273k
31
votes
3
answers
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How do you remove noise to detect just the human voice?
How do you detect different sound frequencies and cut off parts in an audio file? Among instruments, how do you pick up the human voice?
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votes
4
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Filtering beat-to-beat heart rate data
From an experiment, I have a dataset of beat-to-beat heart rate data: a list of the time between each heart beat in [ms].
The data is measured using an infrared optic sensor at the finger tip. The ...
- 1,638
27
votes
4
answers
9k
views
Computing and plotting a spectrogram in Mathematica
How can I compute and plot the spectrogram of a signal/time series/data in Mathematica? I have a WAV file, sampled at 44100 samples/second and I want to generate a spectrogram of that data. Something ...
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27
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4
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Savitzky-Golay Filter to smooth noisy data
I do have noisy data and want to smooth them by a Savitzky-Golay filter because I want to keep the magnitude of the signal.
a) Is there a ready-to-use Filter available for that?
b) what are ...
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27
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4
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How fast is my fidget spinner spinning? A sound experiment!
I would like to measure how fast my 6-bladed fidget spinner spins. To do so, after giving it a hard spin, I gently touch the spinner with a wooden stirring stick to create a buzzing sound which ...
- 1,883
26
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7
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Graphical representation of a moving sound source
Some explanation since I have got a specific and another more open-ended question:
I used two microphones in a 90° arrangement (see picture below) to capture sound from a source moving around the room ...
- 8,529
25
votes
5
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Numerical Fourier transform of a complicated function
Say I have a function $f(x)$ that is given explicitly in its functional form, and I want to find its Fourier transform[1]. If $f$ is too complicated to have an analytic expression for $\hat f(k)$, how ...
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Can we use Mathematica to design an electronic active filter?
How can we use Mathematica to design an electronic implementation of an active filter?
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23
votes
4
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Plotting Fourier spectrum versus frequency of a signal
I have looked around here, and i am sure this has been answered, but i don't understand it. The thing is, I have taken a introductory signal processing course, and we had to use Mathematica, and i had ...
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5
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How to find the phase difference of two sampled sine waves?
I'm trying to measure a phase difference between two Sine functions I've acquired with a computer. I'm uploading one of the .txt files with the data I'm working with here: txt file. To remove the ...
- 327
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How do you find the frequency and amplitude from Fourier?
Edit
This is a popular question with several answers. This edit organises the answers and gives links.
Fourier just gives y values (ordinates) if you wish to read off frequencies and amplitudes you ...
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23
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3
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Can one find the beat of a tune with Fourier analysis?
I'm trying to find out if it's possible to find the beat of a tune by Fourier analysis with Mathematica. I'm taking a 44.1 kHz sample sound and hoping that I might get a nice peak for a frequency ...
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21
votes
1
answer
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Extracting information from the result of ContinuousWaveletTransform
I'm trying to analysis a signal and identify some time-frequency information of it. For example, around which time the specific frequency arrives. It appears that Mathematica has very powerful wavelet ...
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20
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1
answer
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How to demodulate an FM signal in continuous-time?
I'm not sure if this is a math or Mathematica question, but I'm posting it here because I'm interested in possible Mathematica tools/functions to solve the problem.
I'm stuck. I want to simulate ...
- 7,018
19
votes
2
answers
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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 ...
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19
votes
0
answers
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Strategies to find curves on messy data using FindCurvePath
I have a set of data points that correspond to roots of a transcendental equation with respect to a parameter (the abscissa) which, by the properties of the system, define continuous curves (might be ...
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18
votes
3
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What is Mathematica's equivalent to MATLAB's filter function?
The MATLAB code
filter(0.5,[1, -0.5], [1:10])
is equivalent to
Rest@FoldList[(#1 + #2)/2. &, 0, Range[10]]
I don't ...
- 15.8k
18
votes
4
answers
3k
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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 ...
- 1,639
18
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2
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Processing images from NASA's Juno Jupiter Orbiter
Question
Can you help me improve what I’ve done to create an enhanced-color picture from an image provided by NASA’s JunoCam? [My work is shown in the penultimate image of Jupiter in this post.]
I’...
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2
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Cluster a signal into areas of equal intensity
Introduction
I have a greyscale photograph that I want to partition into areas of equal intensity.
This means, that the integral over each partition should be (roughly) equal.
There is no unique ...
- 341
15
votes
3
answers
885
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Deleting noisy data from a plot (manually) and export the best remaining data
I have the following temperature time-series. As you can see it contains very very noisy points in some periods (Fig.A). I tried to approach the best data(the black one in the center) based on the ...
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How can I use Mathematica to numerically compute a Wigner spectrogram of an optical pulse?
This question was inspired by this question where it is necessary to numerically compute the Fourier transform of a Gaussian optical pulse with a Gaussian chirp function.
$$E(t)=e^{-t^2} \cos(50 t - ...
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14
votes
1
answer
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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 ...
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13
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1
answer
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13
votes
1
answer
5k
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Hilbert-Huang transform package
I am trying to learn Hilbert-Huang transform (HHT) and its applications (especially in ECG signal processing). There are several HHT packages (scripts) HHT for R and Matlab. Is there any known ...
- 133
13
votes
1
answer
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views
Wavelet transform order problem
I have a signal that I'm trying to study its time-frequency features by continuous wavelet transform. By choosing different wavelet order, I get some differences in the results.
...
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13
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4
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Segmentation of a microscopy image with uneven illumination
I am trying to do a little image segmentation on some cells taken from microscopy images that have uneven illumination. I am having trouble getting the background of the image cleaned up after ...
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11
votes
2
answers
2k
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Correct Fourier scaling and high-resolution frequency identification
I have a dataset of amplitude versus time $(t,A(t))$ and I need to extract the dominant frequency and amplitude, and also get the amplitude at one other specific frequency.
My data looks like this:
<...
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10
votes
2
answers
814
views
Frequency of ticks in mechanical watches
I'm looking to find the frequency of a relatively large dataset (or a relatively short audio file) of a repeating sound, like so:
Here are the original files, for those willing to play. :)
eta2412
...
- 3,051
10
votes
2
answers
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Building Butterworth Bandpass Filters
In order to bandpass filter data it is necessary to use ButterworthFilterModel, followed by ToDiscreteTimeModel and RecurrenceFilter. I have two questions:
I wish to specify the order of the ...
- 16.8k
9
votes
3
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2k
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high pass filter without losing detail
I have troubles doing a simple high pass filtering...
Downloading the test data, you can see that overimposed on the signal there are some low frequencies and an almost constant slope, that I'd like ...
- 1,085
9
votes
1
answer
2k
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Finding outliers in 2D and 3D numerical data
I'm working on dataset which isn't normally distributed.which contains three dimensions like cost, discount and profit
I'm trying to find outliers in all these dimensions. I used z score to find ...
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9
votes
1
answer
1k
views
How can I generate pink noise using Mathematica?
I need a time series of pink noise. How can I generate pink noise using Mathematica?
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9
votes
2
answers
952
views
How can I generate a sin wave with power law noise?
I am interested in simulating a signal with different types of power law noise, as entitled in Wikipedia, "Color of Noise". (The audio examples are pretty cool).
Basically, white noise, ...
- 1,496
9
votes
1
answer
289
views
How to reproduce Spectrogram from SpectrogramArray?
I'm trying to reproduce the result of Spectrogram from SpectrogramArray, but having no luck, any help?
What I've got so far:
<...
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8
votes
3
answers
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Signal processing by means of WaveletTransform
I updated my question to explain what I want.
I have the voltage-time curve from the real industial object. This curve was gotten from the digital oscilloscope:
As you can see it has hight-frequency ...
- 83
8
votes
1
answer
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views
Sample rate severely influences quality of ButterworthFilterModel?
I've hesitated for a while about whether this should be posted to dsp.SE or not, but still decide to discuss it here.
Today I was playing with ...
- 68.4k
8
votes
1
answer
3k
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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 ...
- 31.8k
8
votes
1
answer
1k
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How does Mathematica's LowpassFilter work?
I don't really understand the documentation for the LowpassFilter[] function in Mathematica. In the course I have about signal processing, low-pass filters come in ...
- 215
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votes
1
answer
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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 ...
- 37.4k
8
votes
2
answers
404
views
How to detect discolorations in an image?
I'm evaluating the technical quality of an images and I'd like to scan it for defects from dirty sensors. Are there any filters to quickly detect a blob of discoloration? Here are a few examples:
- 31.8k
7
votes
2
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2k
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How to get a smooth derivative graphic
You can get data by this code:
data = Normal[Databin["fHVr7FSi"]]
Visualize it like following
We can find some non derivable ...
- 27.2k
7
votes
1
answer
548
views
Working example for the built-in SavitzkyGolayMatrix for doing polynominal smoothing
Have been using various packages SavitskyGolay.m for Savitsky-Golay polynomial smoothing but just noticed the built-in matrix kernel. I am looking for an example ...
7
votes
5
answers
1k
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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:
...
- 3,102
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votes
1
answer
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Data filtering using Butterworth filter
I want to filter data using Butterworth filter.
I am currently using Matlab and I want to know how to do it in Mathematica.
I have the following data:
...
- 20k
7
votes
2
answers
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Resources for Sound Synthesis & Design
Are there any resources for sound synthesis using Mathematica?
This page, Mathematica: Audio Synthesis Software, refers to other software packages, e.g. Max/MSP and Csound, for real-time synthesis.
...
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