Questions tagged [signal-processing]

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

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2 votes
2 answers
325 views

how to drop certain data points from a list

...
4 votes
2 answers
182 views

Filtering data with timestamps

How to apply filter to data that was sampled in certain moments of time? Examples from documentation deal only with uniformly sampled data: ...
1 vote
0 answers
41 views

Error using ListCorrelate for Overhang parameters nonzero machine-sized integers

I've encountered a problem using the ListCorrelate function which I haven't been able to solve or find much information on. Using the following code: ...
2 votes
3 answers
1k views

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"]] ...
0 votes
1 answer
79 views

How to get a single evaluation of RandomReal in a Block

I want to generate (and eventually sample) a sine wave with a random frequency in the range [½, 1] (i.e. capture somewhere between half and one period of the waveform over the domain [0,1]). The two ...
0 votes
0 answers
207 views

Fourier Scaling Issue

First a little background: I’ve looked at the following discussions on StackExchange and still racking my head on Fourier What are the most common pitfalls awaiting new users? Discrepancy between ...
21 votes
1 answer
5k views

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 ...
1 vote
1 answer
410 views

remove noise while preserving peak

I have a data (see this link) which has some wiggles at both end. I tried to apply different filters to smooth the data, like this ...
2 votes
1 answer
70 views

Is there a discrepancy between reported and actual SampleRate in AudioGenerator

When AudioGenerator is used to generate an Audio object, there may be a discrepancy between the specified (and reported) SampleRate and the actual time difference between the samples. This was ...
27 votes
4 answers
7k views

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 ...
10 votes
2 answers
1k views

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 ...
7 votes
1 answer
529 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 ...
0 votes
2 answers
438 views

Problem with using Integrate and Plot functions [closed]

I'm pretty new to Mathematica. I'm trying to implement the following 2 lines: ...
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 ...
1 vote
1 answer
1k views

Remove large spikes in data set

I need remove large spikes on my dataset that looks like this: I would like automatically replace the spike with data shown in dotted red segment. Is it possible if I choose the spike interval by ...
27 votes
4 answers
1k views

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 ...
0 votes
1 answer
571 views

Ideal/Brick wall Low/High-pass filters: Fourier approach not working

I am trying to take a signal (as a list) and separate it into the low frequency and high frequency parts around some split frequency f. Given that what little signal processing I ever studied is now ...
30 votes
4 answers
13k 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 ...
0 votes
1 answer
2k views

FFT of data to obtain resonance frequencies and correct amplitudes

I have often to do with experimental data (with a certain length and given sampling frequency) where I obtain trajetories of moving objects in 2d. Then I am interested to find out what the ...
4 votes
0 answers
499 views

Can Mathematica reconstruct an audio signal from a given spectrogram

I just realized that Mathematica can easily construct a spectrogram for a given .wav file. My question is, to what extent can this process be inverted in Mathematica? Namely, lets say I have the ...
0 votes
0 answers
78 views

Is there a complex version of PeriodogramArray?

I am trying to build some functions to help me work with audio data collected as time streams but converted to the frequency domain. The frequency domain results must be complex because phase is ...
6 votes
2 answers
279 views

How to segment nuclei from a noisy image

(data can be downloaded from this link.) I am trying to segment and count nuclei in a noisy 3-D image stack and it is proving to be somewhat challenging. The strategy I could come up with requires ...
0 votes
0 answers
76 views

Prevent running out of memory when doing SpectrogramArray?

I was using SpectrogramArray[Import@"myFile", 22050, 22050]to transfrom a piano mp3 file so that I can (probably?) generate a midi file from that mp3. The step size ...
1 vote
2 answers
267 views

Two-tone spectrogram

The default spectrogram command uses a single color and appears to just vary the saturation of the color to express intensity. So, for example, in the default implementation which looks like this: ...
1 vote
1 answer
2k views

Detecting beat frequency using FFT

I wrote Mathematica FFT code that works for non-beat signals, eg. Sin[2*Pi/20*x] and more complicated but I can't obtain beat frequency of Sin[2*Pi*(10)*x] + Sin[2*Pi*(11)*x]. Also, what is general ...
2 votes
2 answers
234 views

Plot cumulative distribution of a function

I want to calculate the probability $P(X\le-0.5)$. I have the probability density function $1/(\pi\sqrt{A^2 - x^2})$. $A$ is supposed to be the square root of noise power, $A = \sqrt{N_0}$, and so ...
4 votes
0 answers
185 views

FIR filter and the relation between Sample rate and cut-off frequency

I have problem to unterstand the logic of the cut-off frequency of the FIR filter. Suppose my sample rate is 2MHz and I want to design a lowpass filter with a cut-off frequency 100Hz. What will be $\...
1 vote
2 answers
200 views

How to detect the singular value with wavelet analysis

I have a series data data=Uncompress[ FromCharacterCode[Flatten[ImageData[Import["https://i.stack.imgur.com/ApipY.png"], "Byte"]]]]; We can show it ...
1 vote
0 answers
162 views

wavelet fourier transform

I want to do wavelet Fourier transform of my data but I have few doubts in this. 1)first of all what is octive and voice command here when i am changing value according to that my plot is changing but ...
2 votes
1 answer
1k views

Cut off frequency of low pass filter

I have a data here, I want to make sense of Lowpass filtering function in Mathematica.I do not fully understand units of cut off frequency in this option since the data is in frequency space. What I ...
11 votes
2 answers
2k views

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: <...
2 votes
0 answers
245 views

Analysis of the periodic data by the maximum entropy method

I am trying to get the frequency spectrum of periodic data. Since the data set is short, the outcome of the frequency peaks are not sharp enough for me to do further analysis. I know the spectrum can ...
19 votes
2 answers
2k views

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 ...
0 votes
0 answers
92 views

LowpassFilter and LeastSquaresFilterKernel implementation

I'm in the troublesome phase to port Mathematica code into another programming language. I cannot find a proper reference on the algorithm used in the ...
2 votes
0 answers
168 views

Handling oscilloscope bitmap data

I'm using an oscilloscope from Tektronix; its output is formatted as a $n \times (m + 2)$ matrix, where $n$ is the number of vertical divisions and $m$ the temporal scale. The first $9\times 2$ ...
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?
25 votes
5 answers
13k 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 ...
0 votes
0 answers
126 views

Numerical error or mistake when filtering using Fourier?

I am comparing the filtering method using a recurrence filter with filtering using Fourier. I think both methods should give the same answer but they differ by a small amount that could be numerical ...
1 vote
1 answer
68 views

Creating time varying 2d coordinates with OrnsteinUhlenbeckProcess

I see that I can create time varying 1d data with e.g. ...
3 votes
1 answer
140 views

Confused about the usage of AudioSpectralTransformation

The documentation for AudioSpectralTransformation says: AudioSpectralTransformation computes the short-time Fourier transform of audio, maps every value at ...
3 votes
1 answer
2k 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 ...
9 votes
1 answer
2k views

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 ...
2 votes
1 answer
361 views

Implement inverse discrete-time Fourier transform

In Mathematica after version 9. We had ListFourierSequenceTransform to do discrete-time Fourier Transform, but we do not have the inverse function. If we peform it ...
6 votes
2 answers
1k 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: ...
8 votes
2 answers
392 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:
39 votes
3 answers
10k views

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 ...
6 votes
1 answer
267 views

Do 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. ...
6 votes
2 answers
423 views

How to calculate the amount of offset about two list

You can get my data by this code {data1, data2} = Uncompress[FromCharacterCode@ Flatten[ImageData[Import["https://i.stack.imgur.com/ShSMY.png"], "Byte"]]]; We ...
2 votes
1 answer
683 views

How to measure the pulse width in Plot Graph?

I'm practicing "Inverse Fourier transform" with impulse train using Diracdelta function. Condition Wavelength: 800(nm) Velocity of Lingt: 299,792,458(m/s) Using 1 and 2 >> Frequency0 = 299,792,458(...
0 votes
2 answers
157 views

Can't get Mathematica to use FourierTransform in the way I want it to [closed]

I'm an EE working with signals and systems trying to get Mathematica to do a few basic functions to see if I could use it regularly in my work. Here's the code I'm working with: ...