Time-frequency methods provide more viable solutions than Fourier methods for signals that are shorter in time and not necessarily periodic. Methods such as Wavelet and Gabor transforms are considered to be T-F techniques.
Questions tagged [time-frequency]
87 questions
3
votes
4 answers
Infinite looping consumes 100% CPU
I am stuck in a situation where I need to generate a defined frequency of some Hz. I have tried multimedia timers and all other stuff available on the internet but so far an infinite loop with some if-else conditions gave me the best results. But…
Danish
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1 answer
What should I look for in the analysis of the attached signals?
I'm looking to analyze and compare the following `signals':
(Edit: better renderings here: oscillations good and here: oscillations bad)
What you see are plots of neuron activations from a type of artificial neural network plotted against time.…
Ben J
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Discrete Wavelet Transform on images and watermark embedding in LL band coefficients, data is lost when IDWT-DWT is performed again?
I'm writing an image watermarking system to hide a watermark in an image's low frequency band by transforming the image's luminance channel with a Discrete Wavelet Transform, then modifying coefficients in the LL band of the DWT output. I then do an…
Patrick
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Gabor Phase ?? my values are too small
Hi every one >> hope you all are doing fine
I wanted to ask you about calculating the phase values for an image ,, you see I used the Gabor wavlet like so :
k = ( Kmax / ( f ^ v ) ) * exp( 1i * u * pi / 8 );% Wave Vector
kn2 = ( abs( k ) ) ^…
Rand
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1 answer
Realtime STFT and ISTFT in Julia for Audio Processing
I'm new to audio processing and dealing with data that's being streamed in real-time. What I want to do is:
listen to a built-in microphone
chunk together samples into 0.1second chunks
convert the chunk into a periodogram via the short-time Fourier…
user3303504
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2
votes
1 answer
Plotting Wigner-Ville distribution with pytftb on python 3
I am testing wigner ville distribution to see if it works for the estimation of original amplitude of a signal with noise.
The pytftb provides a wigner ville function that works well with their examples. I use it like this:
tfr =…
Danf
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2
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2 answers
PANDAS - Loop over two datetime indexes with different sizes to compare days and values
Looking for a more efficient way to loop over and compare datetimeindex values in two Series objects with different frequencies.
Setup
Imagine two Pandas series, each with a datetime index covering the same year span yet with different frequencies…
Adestin
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2
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1 answer
Time frequency spectrogram in Python
I have some 64 channel EEG data sampled at 256Hz and I'm trying to conduct a time frequency analysis for each channel and plot a spectrogram.
The data is stored in a NumPy 3d array, where one of the dimensions has length 256, each element containing…
Simon
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1 answer
The drawbacks of Short time fourier transform
I have read the following sentence in a documents talk about the drawback of short time Fourier transform, and he is said :
the drawback is that once you choose a particular size for the time
window, that window is the same for all…
user3840877
1
vote
1 answer
Abnormal Y-axis value after performing FFT
I have an UFF file which consists of Vibration data. The objective is to convert the timewaveform signal to frequency domain.
I have written a python script to convert the timewave form signal to frequency domain using scipy.fft.
I have an UFF file.…
1
vote
1 answer
How to Solve Getting nan Entropy in Python?
Based on this paragraph of a paper about brain-computer-interface, I wanna extract time-frequency domain features using discrete wavelet transform and then calculate energy and entropy with the giving equation.
So I've chosen pywt in python, and…
Hanie Asemi
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1
vote
1 answer
Plot spectrogram of overnight sleep EEG using MNE
Is it possible to plot the spectrogram of overnight sleep EEG data in mne? I don't want to create epochs but, have the spectrogram of continuous 8-9 hours. The examples I see in e.g. EEGlab (Matlab) have perfect color distinction which makes the…
TheJohn
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vote
1 answer
1/3rd Octave Band analysis of a noise signal
I want to do a 1/3rd octave band analysis of a noise signal. I have got a time signal representing sound pressure(Pa). I have arrays of the central frequencies and of the lower and upper cutoffs.The final aim is to get a bar chart representing sound…
Rohan Yuttham
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How to convert time domain data into frequency domain data using python
I have a dataframe named dataTime with 4335 rows with 20 secondes between every two rows.
dataTime.shape
Out[630]: (4335,)
enter image description here
I want to plot my data into frequency domain
from scipy.fftpack import fft
import…
zied cheheibi
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How can I get the time and frequency resolution from wavelet?
I've got a little issue understanding wavelet analysis. I report a code from Matlab tutorial
figure;
s0 = 6*dt; ds = 0.15; NbSc = 50;
wname = 'morl';
SCA = {s0,ds,NbSc};
cwtsig = cwtft({Y,dt},'scales',SCA,'wavelet',wname);
MorletFourierFactor =…
Edoardo De Gaspari
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