Tagged Questions

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

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4
votes
2answers
100 views

FindPeaks does not smooth noise on peak?

I have experimental data which is noisy. My objective is to find the peaks. Here is a short part of the data. ...
1
vote
2answers
73 views

Compare two Shifted signals

I have a signal A and a signal B which computed by rotated A spatially. ...
0
votes
0answers
61 views

What's the wrong when I use the BodePlot?

I want to plot this Butterworth filter's TransferFunction: ...
1
vote
0answers
60 views

How to use a Butterworth bandpass filter to generate a chirped signal

As there is no ChirpSignal function in Mathematica, I wrote a simple code to generate a sinusoid with a frequency that changes continuously from frequency ...
5
votes
2answers
249 views

How to generate a chirped signal

As there is no ChirpSignal function in Mathematica, can anyone tell me how to write a custom function to generate a sinusoid with a frequency that changes ...
11
votes
4answers
206 views

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 ...
5
votes
3answers
338 views

How can I obtain a smooth curve from my data but preserve two inversion points

I have a list of data points, {x, y}, my data. When I plot them, the curve is jagged. I want to smooth the curve and preserve the two sharp corners. This is a plot ...
2
votes
1answer
139 views

Wavelet vs instantaneous power spectrum

Following on from a previous question posted by @xslittlegrass and answered by @Sector and others, Extracting information from the result of ContinuousWaveletTransform I'd like to know if it is ...
0
votes
1answer
67 views

Extracting filter coefficients from a transfer function

What is the correct way to extract coefficients (in a form I could use in RecurrenceFilter) from a filter which I have represented as a Mathematica transfer ...
4
votes
1answer
89 views

How do I bandpass a signal in Mathematica 8

I would like to use the bandpassing function that is available in newer versions of Mathematica but not Mathematica 8: ...
4
votes
0answers
71 views

Bandpassing EEG's using Mathematica's Bandpass Function

Let's say we have an EEG signal approximated using a fractional Brownian motion: ...
3
votes
4answers
463 views

Why does Fourier give a shifted frequency?

I have a signal that I want to identify the frequencies in it, I used the Fourier function but I can't get the frequency correctly. Here is a simplified example: ...
0
votes
0answers
26 views

Why I am not getting the same frequency when sampling a waveform? [duplicate]

I am trying to simulate the sampling of a waveform to then apply FFT Analysis to it. Here is the sample code I have now using a square wave: ...
1
vote
1answer
82 views

How to generate a random signal consisting of the specified functions

Let's assume that I have some particular signal on the finite time interval which is described by function $f(t)$. It could be, for instance, a rectangular pulse with amplitude $a$ and period T; gaus ...
4
votes
0answers
139 views

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. ...
9
votes
0answers
142 views

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 ...
4
votes
1answer
175 views

Butterworthfilter data filter

I am currently doing a signal analysis and filtering using Matlab. The filter I am using is Butterworthfilter model to filter scattered data (vector data). I am using Matlab as follows: ...
13
votes
4answers
2k views

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 ...
0
votes
0answers
111 views

Numerical Differentiation of an interpolated list.

I have a synthetic spectrum with a wavelength range of .3 to .7 microns. I have interpolated this spectrum for re-sampling purposes. However, I am also attempting to calculate the first and second ...
2
votes
1answer
259 views

Plotting power spectral density from transfer function

I am new to signal processing. The equations below are given in $LaTeX$. I have the following transfer function (from the Dryden Model) for the two-sided Power Spectral Density: $$S(w) = ...
8
votes
5answers
1k views

How do you find the frequency and amplitude from Fourier?

The problem is that a typical harmonic time history will not have an integer number of cycles in the data. For example, with the following time history you get a numerical Fourier transform. ...
1
vote
1answer
277 views

Plot periodic function from Dirac delta function [duplicate]

Sorry for my bad english. I need to plot periodic function from dirac delta: δT(t)=∑δ(t–n*T), where T - is a constant, and n=-20..20 And after them, plot new function fd=f(t)*δT(t) - discrete signal ...
1
vote
0answers
225 views

Convolve two sets of (x,y) data sets

I have two sets of data in the form a={{.1,2},{.2,3},{.3,4},{.5,6}} b={{0,8},{.1,4},{.2,7},{.3,1},{.5,10},{.6,3}} Both data sets have even spacing, although ...
1
vote
1answer
353 views

Plot Fourier transform of $\sin (2 t)$

I'm trying to plot the Fourier transform of $\sin (2 t)$. I tried using the FourierTransform Function (I'm expecting a peak at w = 2) but it gives me undefined at ...
0
votes
1answer
144 views

ListLinePlot “Cannot Take Positions” error with Fourier of WAV file

When I try to do a Fourier analysis of a WAV file with a sample rate of 22050 I get an error "Cannot take positions". What am doing wrong? ...
10
votes
1answer
285 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. ...
5
votes
1answer
164 views

Looking to create a lesson on sensory perception of sound

I'm looking to show students a lesson on sensory perception, more specifically on masking. I know a little Mathematica but sound processing has evaded me. I would like to create a white noise and ...
3
votes
1answer
98 views

PrincipalValue option of Convolve not working in 9.0.1?

The PrincipalValue option of Convolve is used in this question to define the Hilbert transform. However, in Mathematica 9.0.1, ...
6
votes
1answer
2k views

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 ...
4
votes
1answer
367 views

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 ...
1
vote
0answers
436 views

Doing local FFT on huge 3D vector data cell mesh and visualizing it spatially?

Simulation type: I'm running a simulation with the OOMMF micromagnetics package http://math.nist.gov/oommf/ where are magnet is represented by a mesh of 3 million cells, it gets excited by a ...
25
votes
7answers
905 views

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 ...
11
votes
3answers
1k views

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 ...
1
vote
1answer
340 views

Gauss Markov Process

I am trying to model a 1st order Gauss Markov Process (gyroscope drift). I know the Allan Variance characteristics of the process (bias instability, random walk characteristics). I know the model ...
4
votes
1answer
602 views

How to get the total intensity of a certain frequency range in an audio file?

Does anyone know how to get the total intensity of a certain frequency range in an audio file? Let's say an audio file has a frequency range from 0Hz to 20KHz, and I want to extract the total ...
2
votes
1answer
283 views

Spectrogram of complex exponential functions in Mathematica 9

How can the v9.0 built-in Spectrogram[list, n, d] function be modified to accept complex exponential functions? The V8.0.4 code that produces the result I'm ...
2
votes
1answer
340 views

Obsolete Signal Processing functions

I need some tools to detect the fundamental frequency and pitch of a sound. I Googled for "pitch detect" and found some .nb files that do these tasks, but all the files are in Mathematica 3.0 format. ...
28
votes
4answers
953 views

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 ...
7
votes
0answers
290 views

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 ...
22
votes
5answers
7k views

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 ...
18
votes
1answer
2k views

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 ...
2
votes
1answer
339 views

non-linear trend reduction using thresholds

Doing some mappings of the earth magnetic field results in the left-hand figure below (which consists of 181 profiles): To improve this I tried a non-linear trend reduction using, for example, ...
22
votes
2answers
1k views

Implementing continuous phase/Arg function

In MATLAB there's a function called phase that is just like our Listable friend Arg, but ...
6
votes
3answers
1k views

How to properly plot a response of a transfer function in Mathematica?

I'm trying to display the output response of a transfer function in Mathematica with and without a compensator. The problem is very strange: while the transfer function compensate is showing well, the ...
19
votes
3answers
2k views

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 ...
24
votes
4answers
4k 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 ...
17
votes
4answers
3k views

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 ...
16
votes
3answers
4k views

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 ...