Questions tagged [spectrogram]
A spectrogram is a time-varying spectral representation (forming an image) that shows how the spectral density of a signal varies with time.
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audio spectrogram normalization
I am performing language classification from audio signals using mel-spectrograms as my inputs for a ResNet. It works well as long as all of my audio data from different languages is from the same ...
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31 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 ...
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Spectrogram of chirp sequence radar signals
I am confused as to whether SFFT makes sense to process chirp sequence signals. The radar fires up a sequence of 100 linear ramps with that are only interrupted by the very short period in which the ...
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23 views
Spectrogram power/magnitude normalization in analogy with image intensity normalization
In analogy with the 8-bit grayscale image color depth, in which the intensity of a sample pixel is normalized to a value between 0 and 255 by taking into account the minimum and maximum intensities ...
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finding harmonics from fundamental
https://s3.amazonaws.com/izotopedownloads/docs/rx700/en/interactive-tools/index.html#selection-tools
From the above link, under the "Magic Wand" tool description, how does that algorithm work?
In RX,...
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33 views
Normalizing vectors to be the same size to retain PSD data
Context:
PSD=periodogram(y) in MATLAB gives the PSD (power spectral density) estimate of a sound-source signal. I want to find the local maximum within 3 different ...
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How to Extract frequency bands from Short-time Fourier Transform?
I am reproducing the results reported by the author in a research paper. In which he takes the STFT of EEG signals. The input data has a shape of (1 X500) and I used Scipy library built-in function to ...
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Extracting audio from picture of time-domain signal
I saw this nifty art thing where they dress up the time-domain audio signal in some pretty way.
https://www.etsy.com/ArtbloxShop/listing/621561709/sound-wave-art-custom-soundwave-print
My question is ...
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36 views
How to classify the movement type of a target into two categories(direct motion or else) by using a doppler radar?
How to classify the movement type of a target just into two categories(one is direct motion which is almost straight line movement and the other is anything else) by using a doppler radar with a ...
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199 views
How to go from wav file to spectrogram back to wav file in python?
Close to this question but different : Wav To Spectrogram, Back To Wav
I already posted this on StackOverflow(https://stackoverflow.com/questions/54743968/how-to-go-from-wav-file-to-spectrogram-back-...
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Recover Audio from Spectrogram Image
I have applied transformation(Constant Q Transformation) to my audio time domain signal, this gives me Frequency vs Time representation. Now, the CQT values consists of complex values(84*260), but ...
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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 ...
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What is Causing a Noise Signal in USB Audio Recording?
I am experiencing the following peculiar noise signal when recording from my Behringer Xenyx Control 2 over USB.
There is frequency at around 2293 hz as show:
And over time, it produces the ...
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How to use a context window to segment a whole log Mel-spectrogram (ensuring the same number of segments for all the audios)?
I have several audios with different duration. So I don't know how to ensure the same number N of segments of the audio. I'm trying to implement an existing paper, so it's said that first a Log Mel-...
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58 views
How can I calculate the Number of bins per octave?
I am trying to calculate the Constant Q Transform for Monophonic audio using Python.
The Python has the library to calculate the CQT , the default value of num_bins_per_octave is 12.
How would one ...
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163 views
How to calculate the PSD from the complex calculated STFT?
I have calculated the STFT with scipy python library:
...
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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 ...
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53 views
Fourier like spectral analysis with uneven intervals and redesigned DFT matrix
I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
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Audacity Spectogram view: how to see exact frequency and intensity under the cursor?
In the Spectogram view, simply clicking anywhere with the selection tool gives a vertical line to the top ruler, and shows at the bottom the exact sample, H:MM:SS, or other time coordinate you'd want.
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31 views
What's the right scale to represent a frequency spectrum?
To represent a 16 bits temporal spectrum, it's "easy" : my scale is going from -32000 to +32000. But What's the scale for a frequency spectrum ?
I made that try : I calculated a pure single frequency ...
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94 views
Mirrored Spectrogram Mp3
First of all sorry if this is a stupid question, but I am an absolute beginner in this field and have been trying for days now.
I'm working on a java program that uses fft to analyze audio files.
To ...
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time-frequency masking with shared properties between vector masks
I am working on a source separation problem and I have a logical mask that when applied to the STFT matrix, gives me expected results. The problem here, is that the mask is based on a spectral feature,...
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When does a color channel such as RGB carry more info than a grayscale channel or image?
Typically a gray-scale image gives us more information about an image in terms of a signal processing problem. But when does a color channel carry more info than a gray-scale channel?
I understand ...
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86 views
Spectrogram of 493 signals at a time [closed]
I have been working with some seismic data and recently submitted a paper to a journal.
My seismic data has 493 traces: each trace are 8300 seconds long with sampling frequency of 2000 Hz.
One of ...
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1answer
121 views
Spectrogram Interpretation
I collected vibration data (amplitude and time) on a component that was attached to an engine. Using MATLAB I plotted a spectrogram to see what frequencies it vibrated at.
The code:
...
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137 views
how to create a harmonic mask from fundamental frequency?
Using an algorithm that gives the fundamental frequency across time, example https://www.mathworks.com/help/audio/ref/pitch.html (or some other one?)
how would I then use that, to create a harmonic ...
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170 views
Different ways of decomposing signals into sinusoids
For purposes of generating a spectrogram, the signal can be divided into overlapping chunks, each chunk multiplied by a window function and transformed to frequency domain using Discrete Fourier ...
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83 views
Recommended resources for noise reduction
I know the question What Resources Are Recommended for an Introduction to Signal Processing (DSP)? and I have already read some general DSP books, such as Rick Lyons's "Understanding DSP," and also ...
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281 views
Spectrogram with square or non-square magnitude of STFT: power vs. magnitude
As seen in this question and answer, to do a spectrogram, it's common to plot either:
the square magnitude $|\text{STFT}(\text{frame}, \text{bin})|^2$ ("power spectrum")
the magnitude $|\text{STFT}(\...
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1answer
308 views
Calculating SNR from Frequency-time domain
I tried to analyse the time-frequency of specific appliances. As it shows in the following frequency-time graph
I have High frequency noise from different appliances here. 4096 is the number of ...
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2answers
114 views
Window length in matplotlib's specgram
In the paper about speaker verification I can read that
Two quantities have
to be set: the length of the window and the shift between two
consecutive windows. For the length of the window, two ...
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1answer
46 views
Phase of a signal with multi delayed windowed (rectangular window) signal with different amplitudes
I have a signal $x(t)$ which is composed of multi delayed linear chirps with different amplitudes and phases but they share the same $w$ and $\alpha$, the signal can be expressed as follows:
$$\...
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Spectrogram from scipy.signal with Python
To test the python spectrogram (from scipy.signal) , I've created a signal with 2 harmonics: 2 Hz and 8 Hz. Then I've added 50Hz noise and a trend (https://i.imgur.com/t1SnQck.png). I wanted to ...
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394 views
How do I apply a binary mask and STFT to produce an audio file?
So here's the idea: you can generate a spectrogram from an audio file using shorttime Fourier transform (stft). Then some people have generated something called a "binary mask" to generate different ...
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Teager-Kaiser Energy Operator based Spectrogram
I plotted a normal spectrogram for 3 recordings (left), and their TEO (or TKEO) based spectrograms (right). I wanted to understand/read the differences between the left and right pictures. I do ...
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103 views
Spectrum of received signal from radar fm-cw
I obtained actual data from a researcher, consisting of a matrix composed of several received signals from an up-ramp fm-cw radar.
Wouldn't be reasonable to plot the spectrogram of a ramp up and ...
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129 views
What unit is the z axis of a power spectrogram of audio?
the question might seem dumb but since I tried it out and got values well above 2000 (watts?) it got me thinking... Check this out:
...
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1answer
158 views
1D signal to 2D spectrogram
I struggling at transforming a 1D breathing signal into 2D spectrograms,
power spectral density as a function of time and frequency.
Does anyone have an idea about that?
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1answer
71 views
nearest neighbor implementation matlab
I am trying to implement this research paper:
I understand everything in the paper except the part about the nearest neighbors calculation (section 3).
The only MATLAB function I can think of that ...
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208 views
How to manipulate output of Matlab's 'spectrogram' function for additional spectral analyses
all,
I have an audio recording that contains several frequency-modulated elements (think animal calls like birds/bats). I have read this file into Matlab using 'audioread' and plotted the oscillogram ...
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Is there such thing as harmony independent timbre characteristic of a sound?
I was wondering if any of you know about any technique to extract a harmony (e.g. harmony in a shape of a chromagram) independent timbre characteristic of a sound frame.
What I'm after is a version ...
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1answer
119 views
CMV: COLA constraint is not necessary
In the literature on the short-time Fourier transform (STFT) it is often stated or implied that the constant overlap-add (COLA) constraint must be satisfied in order for the STFT to be invertible.
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195 views
How to determine the frequency of each row in a MATLAB spectrogram
I recently learned how to manually compute a spectrogram of an audio signal, which is essentially a matrix. Each column corresponds to a time frame (e.g. 10 ms or something) but I'm asking which row ...
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1answer
116 views
Add noise/signal to mel log spectrogram
I have a predicted mel log spectrogram $S$ and I want to add a noise signal $\eta$ to it.
S = log(mel-filterbank(abs/real part of(stft(signal)))
The naive way ...
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1answer
216 views
Apply windowing before FFT or after?
I am computing a spectrogram and I've found a code example online which goes like this:
...
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1answer
316 views
chirp signal - Frequency spectrum characteristics
I am confused with my own intuition of the frequency response of a chirp signal.
In this case, the chirp signal is a frequency modulated signal with initial frequency starting at 100 Hz and ending at ...
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2answers
376 views
Quantify the difference between two audio spectrograms
I have two speech signals of the same length. They contain the exact same speech content but are recorded from two different microphones. I want to compare the differences between them.
1) Assuming ...
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1answer
60 views
is there a way to apply a median filter diagonally?
For example, some studies show how to smooth a spectrogram with a 2D median filter vertically and horizontally (along time or frequency). My question is how would I apply 2D median filter along the ...
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155 views
Reconstruct signal from its Spectrogram only
The spectrogram of a signal throws away the phase information, but it is said to be possible to reconstruct the signal only from the spectrogram [1] via
$$s(t) = \frac{1}{2\pi s^*(0)}\int_{-\infty}^{\...
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1answer
193 views
Distinguish harmonic sounds from non-harmonic
I am trying to distinguish harmonic sounds in the range from $100\rm \ Hz$ to $1000\rm \ Hz$ in my audio recording.
I attach the spectrogram ($y$-axis is freqeuncy and $x$-axis is time) of a typical ...
