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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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Advantage and Disadvantage using Mel Spectrograms over STFT in speech/waveform synthesis

I want to ask you a question about the waveform synthesis or more spesifically speech synthesis. Most of the state-of-the art papers use mel-spectrograms as their inputs, because it mimics the human ...
Yalçın Cenik's user avatar
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Discontinuities in the frequency domain

I'm trying to implement a waveform such the frequency will look like this - $f(t)=f_0+\left(f_1-f_0\right) e^{\frac{\left(t \pm \delta_t / 2\right)^2}{2 \sigma^2}}$ To do so, I calculate it like this -...
Yarden Sharabi's user avatar
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Octave specgram: How do I plot negative frequencies

I have a complex signal and I'm trying to use Octave to plot a spectrogram. I found the specgram function, and it's close to what I want, but I can't figure out how to get it to display negative ...
Sittin Hawk's user avatar
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Visually identifying audio noise

I have an audio file consisted of a sole 440 Hz sinusoidal wave, which can be heard here. After some manipulation, I've added a noise to it, resulting in a second audio file, avilable here. The noise ...
JohnCalms's user avatar
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Two synthetic signals with same frequency result in two different spectrogram results

I have two signals of the same wave $f(t)=\sin(2\pi\cdot 70\cdot10^6 t ), t \in [0,1e-3] $, which I created with Matlab synthetically. My first signal has 1e6 samples and the second has 1e5 samples. <...
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Calculation of the discrete cosine transform

I am wanting to use the discrete cosine transform to relate the autocovariance function of a process to its periodogram. Following Chris Chatfield's book (Time Series Analysis, p129), I am wanting to ...
hydrologist's user avatar
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How to get Power Spectral Density of file using this research paper method?

I came across this research paper. In this they have mentioned power spectral density calculation of various file. I have read the paper and try to calculate and plot the graph, don't know it correct ...
i_am_learning's user avatar
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Proper audio noise and artifact detection approach

I'm working on developing an audio device testing suite (for speakers and like). I'm looking for approaches to detecting two types of noise: static such as white or pink noise and artifacts such as ...
Sealer's user avatar
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jumps in spectrogram of frequency ramping

I create spectrogram of a sine wave that changes its frequency from 60 MHz to 70 MHz over a period of 1 millisecond. can someone help me understand why I see those jumps? how can I make it smoother? <...
Yar Sha's user avatar
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Audio Classification

Most of the paper about audio classification has worked like this they have specific sounds class wise and the did classification. What if the audio files i have collected have two different sounds at ...
Mudassir Ahmad's user avatar
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290 views

Overall spectrum computation from Short-Time-Fourier-Transform

I am trying to computing the overall spectrum of a given signal from its Short-Time-Fourier-Transform. I am using python to do this and I wrote my function to compute the STFT: ...
Ciccios_1518's user avatar
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1 answer
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Numeric Derivative Frequency Response

It seems quite common to use np.diff() for removing DC components of signals when plotting spectrograms. I noticed some unexpected behaviour during analyis which ...
Daniel Wait's user avatar
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3 answers
216 views

FMCW Radar - What's wrong with the transmitted signal model?

I am new to FMCW radar and trying to plot the transmit signal over time. As you know, the transmitted signal is modelled as: $$s(t) = cos(2\pi f_c t + \pi S^2),$$ where $S = BW/T_{chirp}$ is the slope,...
pej's user avatar
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2 votes
2 answers
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Anonymize / Obfuscate speech when doing audio classification

Let me preface that I am new to audio processing and audio analysis ;) (I asked the same question on reddit, I wanted to increase it's reach)) I am trying to classify specific events (like a gong or ...
Hurricane's user avatar
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Artifact during this STFT spectrogram plotting

I am new to the field of DSP and I am currently working on implementing a real-time audio spectrogram using STFT technique. While making progress, I have encountered an issue when testing a constant ...
Sergio's user avatar
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Plotting a Manually made Spectrogram with python

I'm following a guide about signal processing, but since I'm a fresher to the domain, the guide just stops at a point where only a function that could return the spectrogram values is written. So, my ...
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Extracting features from spectrogram - a curious duplication step

In sound anomaly detection, I see a processing step that I am not able to understand. We derive the Mel spectrogram the standard way. The signal shape is (say) 64 Mels by (say) 313 time bins. So far ...
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Finding phase of a received signal using spectrogram function

I am trying to find the phase of my dataset between a range of frequencies. I can't post my code or data but generally speaking, the frequencies range from 10 to 100kHz and I need the phase between 20 ...
PrematureCorn's user avatar
2 votes
2 answers
435 views

Trying to simulate a Fourier transform spectrometer in Python

I'm trying to simulate a Fourier transform spectrometer in Python. I started basically with a simple single frequency (f=1e10 Hz) sine signal coming into the spectrometer. I obtained the following ...
Apinorr's user avatar
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Mel scaled spectrogram, are filterbanks uniformely spaced with respect to the Mel scale?

So, I'm currently studying the Mel spectrogram and I'm struggling to understand one thing: suppose I have a spectrogram for an audio signal that was sampled at $44100$ Hz (i.e. a Nyquist Frequency of $...
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How do `n_fft` and `win_length` determine the window in spectrogram?

I am currently trying to understand librosa.feature.melspectrogram in a mathematical sense. In my understanding, spectrogram is based on the STFT which is for a ...
esh3390's user avatar
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2 answers
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Scipy and Matlab Spectrogram not matching

I am trying to replicate a spectrogram from MATLAB in Python. I've read other posts but they either don't use complex data or the data doesn't match between languages. I've defined my FFT length (<...
PrematureCorn's user avatar
1 vote
1 answer
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FFTs, Spectrograms, and Units

I am new to signal processing and I have likely a very easy question but I have found inconsistent answers everywhere. When performing an FFT, does it matter what units the amplitude is in? Currently ...
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Wigner-Ville distrubution on large data signal analysis

I have a touch signal on a plate recorded with 3 accelerometers with a sample rate of 150kHz over a duration of 5 seconds (so 750k samples). The goal is to localize the position of the touch in the ...
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How to interprete the standard deviation of the psd in dB?

I have done a power spectrum density estimate using Bartlett's method. However, I was wondering if it is also possible to get a sense of the variation of the averaged spectra. I have plotted the mean ...
Helmut's user avatar
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Algorithm or a tool to compare two spectrogram outputs for unit testing purposes

I am looking for a good algorithm or a tool to compare two spectrogram outputs for unit testing. I can visually confirm the outputs are similar but I would like to automate this process. The basic ...
Dilshod Tadjibaev's user avatar
2 votes
3 answers
573 views

Does overlapping windows while processing a signal produce a stretched time domain?

I'm very new to signal processing and attempting to implement a spectrogram generator to learn more about DSP in general. So far, I have built up an understanding of how I might do that. Get input ...
acd's user avatar
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6 votes
3 answers
857 views

Units of 6.02*N + 1.76 as an FFT noise floor

I'm working on estimating the FFT noise floor for a data acquisition system my colleagues and I are designing. I've read MT-001 several times. In general, I think I get it. However I'm a little stuck ...
FooAnon's user avatar
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3 votes
1 answer
148 views

Uniform density 2d peak detection of spectrogram

I am trying to recreate the algorithm used by Shazam to recognize music, as outlined in the paper An Industrial-Strength Audio Search Algorithm. The algorithm performs a specialized peak detection to ...
Jonathan's user avatar
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averaging power spectrum from multiple signal of different length

I have multiple physiological signals (EMG - muscular electrical activity) that are all of different length (one may even be 2/3 times longer than the smallest one). These signals are from 2 types of ...
Hattori's user avatar
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How to restore spectrogram to audio? [duplicate]

I used the following code to convert the audio to spectrogram, now I try to get the spectrogram back to audio again, but don't know how to write the code. ...
Yanmo's user avatar
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2 answers
247 views

python plt.specgram the number of xaxis' value when I change nfft, overlap

I am trying to use plt.specgram But I found something weird in the x-axis setting. My data is as below.. ...
Lover Coffee's user avatar
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2 answers
141 views

How do I distinguish a 49.90 Hz sine wave from a 49.95 Hz one in a short audio recording?

I've read an article about "mains hum" forensics in http://hummingbirdclock.info/about and about Electrical network frequency analysis. The idea is to be able to measure the small variations ...
g6kxjv1ozn's user avatar
2 votes
1 answer
1k views

Log Mel Spectrogram vs Log Mel Power Spectrogram

I'm doing some feature extraction on audio signals. $M$ being a mel filterbank matrix, and $S$ being the spectrogram (extracted from the Short Time Fourier Transform of my audio signal), we can ...
Jdip's user avatar
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1 answer
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Spectrogram of a shock event

I have measured data of a vibration with chirp input were I suspect unwanted shock events occurred. I therefore thought about computing the spectrogram of my time histories to check the frequency ...
Rhei's user avatar
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7 votes
1 answer
128 views

Can I "reverse" spectral leakage by solving a linear system?

When I compute a spectrogram of (say) a piece of music, there is a lot of frequency "smearing." Often we can reasonably expect that the "true" generating process is much sparser in ...
Michael Kayser's user avatar
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1 answer
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What make sample rate affect QspectrumAnalyzer output?

Use QspectrumAnalyzer to analyze signal,set sample rate as 8M and 32M. I get different output as below,32M sample rate cause ...
kittygirl's user avatar
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1 answer
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How to modify spectrograms so that there is no effect of amplitude on their classification?

Is there any way to bring different classes of spectrograms to comparable amplitude levels so that when they are used for classification, the deep learning algorithm focuses on other aspects (like the ...
nasrin's user avatar
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3 votes
3 answers
235 views

Using spectogram to speed up a signal - Time Scaling/Phase Vocoder

Background About half a year ago, while learning about spectograms as part of an Image Processing course I took, I was told you can speed up audio using spectograms as follows: Calculate the ...
snatchysquid's user avatar
1 vote
0 answers
636 views

Spectrogram of x,y,z data from accelerometer

Using scipy.signal.spectrogram for creating spectrogram and matplotlib's pcolormesh for plotting. I'm working on a project where I'm using a spectrogram to visualize the frequencies of the ...
Mathias's user avatar
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0 votes
1 answer
825 views

what the difference between spectral density and the power spectral density?

What is the difference between the spectral density and the power spectral density, Or they are the same thing? In fact, I find this term in the book of GODA 2000.
Tarek's user avatar
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0 answers
39 views

How is 76 frames calculated mfcc for 1 sec signal with 25 msec window and 10 msec overlap?

I was studying about keyword detection and while doing some reading, I read we take 1 sec audio signal. We then divide it into 25msec sub sections with and overlap of 10msec. We apply mel filter bank ...
t0mkaka's user avatar
2 votes
1 answer
333 views

Performing STFT after Butterworth Filter Seems Lower in Resolution

I have a signal recorded at 2MHz sampling rate. Before any decimation might be required, I first looked for peaks in my periodic recorded signal using STFT/spectrogram. From here, I can clearly see ...
rshah's user avatar
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-1 votes
1 answer
276 views

Why does using a log scale ruin (warp) my scaleograms?

I'm trying to make a scaleogram of neural data using the continuous wavelet transform (with Morlet wavelets). As a starting point, I use just a simple sine wave built from two frequencies, 50 and 80 ...
neverreally's user avatar
1 vote
2 answers
152 views

Good interpolation functions for downscaling magnitude spectrums

I'm trying to downscale a 1D FFT (for displaying an audio spectrogram, like this: My question is: assuming I have a 512 bands spectrum, what would be the recommended interpolation algorithm to ...
Jean-Michaël Celerier's user avatar
1 vote
2 answers
1k views

Reconstructing Audio From Spectrogram (Using it as a filter)

Given a spectrogram calculated using the following code: ...
rshah's user avatar
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1 vote
1 answer
332 views

Artifacts on frequency spectrum

I made a spectograpm in C that takes in a wav file (44.1kHz), converts it to 8bit pcm(can't go higher because of memory constraints) and does 1024 sample FFT on a number of bins, using Welch method. I ...
math101's user avatar
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1 vote
3 answers
1k views

How to do high-resolution FFT on just the lower frequencies in a signal?

Description of the data and problem: I have a signal sampled at 1000 Hz. I'm low-pass filtering it at 120 Hz, and want to make spectrograms of the frequencies below this threshold. I'm using the scipy ...
neverreally's user avatar
0 votes
1 answer
419 views

How to select parameters suitable parameters for a spectrogram

I have a limited background in DSP but I need to generate a spectrogram of an electrocardiography (ECG). I am using the scipy.signal.spectrogram and I need to set ...
bherve1998's user avatar
1 vote
0 answers
442 views

Spectrogram normalizaion to train a Fully Convolutional Model for Audio dereverberation

I'm trying to implement a deep learning based dereverberation algorithm. The network I am using is inspired by the U-net. The idea is to supply the reverberated spectrogram as input and 'clean' it ...
Lorenzoncina's user avatar

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