Questions tagged [scipy]
The scipy tag has no usage guidance.
92
questions
0
votes
0answers
42 views
How to calculate PSD if i have power vs freq spectrum?
i have a signal something like this
how to calculate PSD?
i have freq from 191000200 to 196500000
time gap or delta t = 1 or 2 sec, (what i mean is [tn] - [tn-1])
i will be computing in python any ...
0
votes
0answers
8 views
Python, Is there a way to find the properties of a subregion within a larger image region?
The goal: I have images with particles that I need to find the area of. Each particle also has four to five sub-regions that I need to know the area of. Think of a bunch of stripped shirts in a ...
3
votes
2answers
231 views
Are IIR filters (and specifically Butterworth filter) causal?
I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
2
votes
0answers
52 views
Filtering a square signal with a median filtering to preserve the edges
If needed, you can find my first post for this problem here.
I am trying to clean the following signal:
As proposed in the comment, I tried to use this post proposing 2 methods: median filtering and ...
1
vote
1answer
14 views
How do I set window length and shift length for computing STFT on Scipy?
Does nperseg=32, noverlap=16 mean the window length is 32mS with a shift of 16mS?
Refer here for more details
0
votes
1answer
24 views
Showing specific values in an STFT plot
I have a short term fourier transform plot that I plot using matplotlib's pcolormesh() function:
If I zoom in the plot, I see this:
Now, I want the plot to just ...
0
votes
2answers
99 views
Complex Samples (IQ) - Baseband Filtering
We are currently analyzing a large set of IQ samples in a desktop application and we are interested in implementing many different bandpass filters dynamically.
We realized, that working with scipy ...
3
votes
0answers
29 views
Are there any tools for generating fixed point filter implementations?
It's very easy to make a filter in Scipy or many other tools, but implementing this filter in fixed point in C or VHDL/Verilog is always a chore. I mean, in theory it's just a matter of adequately ...
0
votes
0answers
19 views
scipy.signal.deconvolve not working, Blind deconvolution in python
I am trying to deconvolve my original signal with a given wavelet (Ricker wavelet). But scipy.signal.deconvolve is not giving any output to the signal.
Impulse signal can be generated by below code.
...
0
votes
1answer
33 views
Difference between freqz vs freqresp in scipy?
I'm always confused that scipy has
scipy.signal.freqz, but also
scipy.signal.lti.freqresp / ...
1
vote
2answers
64 views
Hilbert transform with scipy.signal
I'm coding with python and I just started to use the Hilbert transform from scipy.signal. Consequently, to check the result I got I tried to verify a property of ...
0
votes
0answers
31 views
Why is there a difference in the spectrum of an audio file between Sonic Visualizer and my Python script?
I am working on a script which is creating a spectrum analysis from an audio file using SciPy and NumPy. Before I started, I analyzed the file using Sonic Visualizer, which got me the following result:...
0
votes
0answers
51 views
Lowpass Butterworth filter equation
I am using a 5th order lowpass Butterworth filter with a varying cutoff frequency, $f_c$, to smoothen some data coming from a spectrometer. An example of a spectrum, plotted with the filtered data, ...
0
votes
0answers
18 views
constructing and initializing a normalized lattice filter using scipy
I'd like to implement a 2nd order bandpass filter in scipy using a normalized lattice architecture. (I'm choosing a lattice because it's guaranteed stable even when changing the coefficients on a ...
0
votes
1answer
32 views
How to Save FFT output for fast read-in?
For a project, I'm reading in hundreds of short (4 sec) wavefiles and giving them to scipy fft for the frequency information for further processing/experimenting in various ways. Problem is, I want to ...
0
votes
1answer
140 views
Why is the number of frequencies decomposed in scipy.signal.stft() equal to the hop size?
I asked this over on StackOverflow first but figured you fine people might know more about signal processing (duh).
I'm trying to calculate the spectrogram of an audio file in python. There's a nice ...
0
votes
1answer
98 views
Decimating Non-Uniform large time-series data
I'm working with accelerometer data that is sampled at a non-uniform rate. There are major gaps in the data. Below is a scatter plot of the data
I can also give a sense of the frquencies at which ...
1
vote
0answers
33 views
SciPy - Distinguish between two group of periodic samples [closed]
First of all, I'm sorry for my bad English writing, plus, I'm new to DSP.
Background
We have got motion data of 20 cows. 10 cows are healthy and 10 cows are slightly lame.
Lameness is an abnormal ...
2
votes
2answers
100 views
Why is my signal attenuated after applying a HighPass-filter?
I am new to DSP, but I've been attempting apply a butterworth high-pass filter on a 1D array (Values peeking at 300~) to eliminate any noise, yet when applying a high pass filter, I'm ending up with ...
1
vote
3answers
2k views
downsample signal to a specific number of samples in Python
The Python Scipy library provides several functions to downsample signals, but they all have limitations:
The resample function is based on Fourier method, which means it assumes periodic signals.
...
0
votes
0answers
29 views
Is there a way to get output in second order sections (SOS) format from Scipy's signal.firwin
I am using Scipy's signal.firwin to implement a lowpass filter. Using the rule of thumb formula(s) to estimate the order of the filter, I am getting a very high number. I looked into this question, ...
0
votes
1answer
311 views
Demodulation of FSK signal
What kind of FSK signal is this and what demodulation technique can I use to demodulate it. Why is the phase of the 1's changing like that and how does that effect how it needs to be demodulated. I ...
1
vote
1answer
281 views
SciPy Lfilter issue
For one of my DSP projects, I decided to use python to perform signal processing. While I am new to python, I understand that it is a very powerful and versatile language. For my processing, I opted ...
3
votes
5answers
552 views
What Are The Semantics Of Wav-File Sample Values?
The title is the question. To make this concrete, assume I have a standard 16-bit single channel wav file, with (although it doesn't matter) a 16000 Hz sampling rate.
Each sample magnitude will be a ...
0
votes
1answer
141 views
How to implement Matlab welch in python with the same result?
I want to implement Matlab pwelch function in python.
The Matlab code is shown blew:
[PSD,f] = pwelch(data,length(data),[],[],2000);
which data is a row vector ...
1
vote
0answers
60 views
Why are low frequency peaks not sharp in scipy fft?
I am using numpy/scipy to plot graphs of sine waves. frequencies at 15 Hz or higher give nice, sharp peaks, but at lower frequencies, the peaks are smeared and the actual peak frequency can't be seen ...
0
votes
1answer
35 views
Can't seem to get welch function in scipy work correctly
I'm trying to learn DSP through using Python's scipy package.
I have measure some 200Hz signal from a machine. Now I want to inspect the spectral density of the signal. Here's the signal plotted out:
...
0
votes
2answers
822 views
Python Hilbert does not seem to calculate the envelope
I am following the example from: https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.hilbert.html
And although I can replicate their example, it does not work with my data.
This is the ...
0
votes
1answer
96 views
Bandpass filter with very high sampling rate
Consider a bandpass filter with Low Cut 17Hz, High Cut 22 Hz, Fs = 45000 Hz and Order = 6. When I pass a mixture of multiple sinusoidal waves through this filter (with a sine wave of frequency 20 Hz), ...
0
votes
0answers
79 views
Negative Exponential Filter SciPy
I'm trying to transform a time series with a recursive filter to model a feedback.
I was able to do a simple filter like :
...
0
votes
1answer
650 views
How to convert a spectrogram back to a signal [duplicate]
I'm converting a signal to a spectrogram, manipulating that (nonlinear stuff), and then want to use the modified audio signal. I can make it so the segments are not overlapping, but am unsure how to ...
1
vote
1answer
44 views
How to pad a array representing music to pad the stft of this array?
I have an array named samples of size (2, 1321967) representing an audio file. When I pass it to scipy stft with
...
0
votes
2answers
293 views
Delay in Savitzky-Golay filtering
I am applying a Savitzky-Golay filter to a signal, using the scipy function.
I need to calculate the lag of the filtered signal, and how much is it behind the original signal.
Could someone shed ...
0
votes
0answers
90 views
Scipy Deconvolve help
I was playing with the deconvolve method in scipy and I can't seem to get it working properly (I am still really new to DSP/deconvolution). I convolved a gaussian with a fwhm of 2.0e-9 with a ...
0
votes
0answers
225 views
Filtering out different narrow-band frequencies at once
I have asked a closely related question on SO at https://stackoverflow.com/questions/55168460/python-implementation-for-filtering-out-multiple-distinct-narrow-band-frequencie
but I am still unclear ...
1
vote
2answers
1k views
Third octave bandpass filter with python
I am very new to signal processing and coding which is why my questions might be really basic. I have a signal of the acoustic pressure p'(t) and I would like to use a third octave bandpass filter in ...
4
votes
2answers
197 views
Checking Parseval's Theorem for Gaussian Signal by Using Scipy
I'm trying to check Parseval's theorm for Gaussian signal. It's well known that fourier transform of $\exp(-t^2)$ is $\sqrt{\pi}\exp(-\pi^2 k^2)$. So I implement it by using quad and simps. I think ...
0
votes
0answers
60 views
Scipy Welch's gives different first element
I've re-implemented Welch's method and want to compare it to scipy.signal.welch. However, the first two and last elements of the resulting array are different.
My ...
2
votes
2answers
430 views
Why does a higher sampling frequency mess up my bandpass filter?
I was designing a bandpass filter in python using some of the scipy.signal modules.
I am plotting the frequency response of my filter to verify that my desired frequency is in the passband. However, ...
0
votes
2answers
982 views
How to calculate the PSD from the complex calculated STFT?
I have calculated the STFT with scipy python library:
...
0
votes
0answers
89 views
How to know the time of my window to calculate the STFT with python knowing only the length?
I am trying to implement a work presented in an IEEE paper where they have mentioned that the STFT was performed on the signal measurements to obtain a spectrogram with no overlap window of 3 min :
I ...
0
votes
0answers
89 views
how to detrend a carrier phase with butterworth filter?
I am new with detrending techniques, I have a carrier phase measurements and I want to detrend it by 6th order butterworth digital filter. After creating the digital filter I get its numerator (...
1
vote
1answer
6k views
Write a 440 Hz Sine Wave to .wav-File using Python and SciPy [closed]
This is my first post on DSP.SE! I'm a student in Computer Sciences and am just getting started with Signals and Systems, thus getting in touch with discrete signals and analyzing them.
I wanted to ...
5
votes
1answer
2k views
Scipy resample, “fourier method” explanation
I am seeking explanation of what "Fourier method" is that is described for resampling in documentation of resample() method. I want to downsample an array. I know what decimation is and how it works, ...
2
votes
0answers
557 views
real refractive index from Kramers Kronig relation
I have a measurement of the complex part of the refractive index $k$ (where the refractive index is $m = n + i\,k$) measured at a nonlinear grid of wavelengths or frequencies that span several orders ...
1
vote
1answer
3k views
How to filter out those outliers
I'm struggling to filter some data from an accelerometer. I need to do it in python (and not just on the device collecting the data) to fix the data I have, so that I can build some classification ...
2
votes
1answer
2k views
Amplitude of frequency bin in FFT doesn't match time-domain amplitude
I have a sinusoidal current that I am sampling at about 357k SPS. The current signal is about 3A pk-pk @ 750hz (top figure). I am wondering why when I take the fft using numpy/scipy's fft function, ...
1
vote
1answer
809 views
How to Apply Gaussian Filter to Raw Audio Files in Python?
I am recording raw files in python to later break them into phonemes, but the noise in the surrounding environment is hampering the result. So, there is a need to apply a filter to the recorded raw ...
3
votes
3answers
634 views
Decreasing Sample Rate in DFT (FFT) for Audio Analysis
I'm working with audio data analysis through FFT algorithm.
My example audio is a sine wave at 440 Hz and 44100 Hz sampling rate.
FFT methods in programming, like ...
6
votes
1answer
331 views
Morphing between two FFTs
I'm a musician and I'm making a script that takes a wave file and snaps each of its frequencies from the fourier transforms to the nearest musical harmonic. Thanks to help from another question I ...
