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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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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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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29 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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54 views
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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31 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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108 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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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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107 views
How to calculate the PSD from the complex calculated STFT?
I have calculated the STFT with scipy python library:
...
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37 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 ...
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1answer
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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1answer
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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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1answer
29 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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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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13 views
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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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
100 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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1answer
110 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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163 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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81 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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242 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
261 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
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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
45 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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2answers
2k views
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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326 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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93 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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1answer
124 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
143 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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204 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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2answers
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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
112 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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What is the difference between spectrogram and spectral envelope, if any?
I am working on different vocoders Griffin-Lim and WORLD. They use spectrogram and spectral envelopes respectively by definition. I wonder the difference between these two representations.
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2answers
175 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
103 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
211 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
293 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
342 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
56 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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150 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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145 views
Spectrogram parameters for Audio Fingerprinting
I'm using the specgram() function in matplotlib library to get Spectrogram of songs for Audio Fingerprinting (for musics) and making unique hashes for each song (something like shazam) and im sure im ...
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1answer
167 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 ...
