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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1answer
328 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 ...
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2answers
3k views

STFT computation

I'm trying to compute the STFT by my self. Thus, I wrote the following code: ...
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1answer
1k views

Is it possible to recover a waveform from spectrograms of magnitude *and* phase?

It is my rough understanding that a typical spectrogram discards phase information by squaring only the real-valued part (magnitude) of the STFT (I know it's not quite this simple, but feel free to ...
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1answer
155 views

How can you 'perfectly' reconstruct phase for transients in a modified audio absolute spectrogram?

I am currently working on the absolute spectrogram of an input audio signal. I am using non-negative matrix factorization to separate out the rhythmic components (bass drum, snare drum and hi-hat) of ...
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2answers
137 views

What's a good physical description of the following matlab code?

I've inherited some matlab code and I can't really understand what the resultant signal really means. The input is audio and the code first performs an STFT/spectrogram (sliding window FFT of size ...
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1answer
5k views

scipy.signal.spectrogram

I want to do time-frequency analysis of a signal. So i decided to use spectrogram function from scipy. This function returns, three parameters f,t,Sxx. I am using below arguements: x : my signal fs : ...
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2answers
70 views

What can i find in a spectrogram?

What information can i read from this spectrogram? I have 2 signals, the first one a sine and the second one a sine with noise
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0answers
315 views

Hilbert Spectrum vs. STFT

If I wanted to plot a spectrogram of a signal, I would by default use the Short Time Fourier Transform. However, the Hilbert transform does something similar: it lets us calculate instantaneous ...
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2answers
2k views

Self studying, getting a quality spectrogram

So I've been self studying signal processing, and been trying to use Python to get quality spectrograms, quality spectrogram like the one that would be produced with audacity etc. The steps I have ...
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1answer
619 views

relationship of column of spectrogram to original signal

We can get the spectrograms of a signal which is a 2D matrix. How do I get back from the columns of the spectrogram to the time stamps in original signal? For example, what time stamp does the columns ...
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1answer
616 views

Is the Auditory Spectrogram the same as the Magnitude Spectrogram?

This is in the context of speech signals. The magnitude spectrogram is computed by framing the signal into short time windows, applying a hamming (or similar) window, computing the fft over each ...
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3answers
600 views

Spectogram of a signal

I am working on a seismic signal to extract long period long duration earthquakes. The sampling frequency is $2004\ \rm{ Hz}$ and the the signal has $20755200\ \rm{samples}$. The spectogram seems to ...
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1answer
224 views

Speech signal formant spectrogram. How can we determine F1?

The formant spectrogram in this page points F1 and F2 as below; In bottom-right F1 movement, I thought F1 could be below blue one. But how can we determine F1 is upper one not below one? Is it ...
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0answers
450 views

Smooth looking spectrogram display

I'm working on a simple sound analyzer application and a main feature of this program is the spectrogram display. I want this spectrogram to render fast and to be good looking while preserving all the ...
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2answers
654 views

Combining spectrograms with different windows to getting arbitrary time and frequency resolution

Spectrograms convert an amplitude-time signal into a frequency-time signal using Short Time Fourier Transform (STFT). The window size L used in STFT is a design choice. As L increases, you get higher ...
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1answer
57 views

Should zero element be considered to calculate mean when smoothing spectrogram by window?

My (mass spectrometry) spectrogram does not measure the intensity constantly. I obtain the spectrogram, for example, ...
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2answers
541 views

How to deal with audio with different length in Audio Classification

Currently, I am trying to work with the Dataset UrbanSound8K to try some Audio classification. And I got stuck in the preprocessing step already. Since the audios are of different lengths, like 4 ...
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2answers
596 views

What is the amplitude range of a spectrogram?

Is there an upper and lower bound to a spectrogram representation of an audio signal? The range of the amplitude values of the audio signal is from 0 to 1.
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0answers
211 views

How to calculate spectrogram from nonstationary, nonuniformly sampled signal

I have a high resolution 3D spatial signal (xy-elevation data collected via Terrestrial Laser Scan) with very nonuniform sampling (holes/shadows due to vegetation; point spread varies as a function of ...
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1answer
149 views

Continuous wavelet transform subsampling at lower frequencies?

I am not completely confident in my understanding of wavelet theory, but since I am currently in the process of creating a CWT scalogram tool, I have to ask: Is there a theorem allowing us to ...
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2answers
830 views

how to use image filters for spectrograms?

Using MATLAB, I can import an audio signal and use some FFT function to get the spectrogram into the workspace. My question from here, is how to then process this spectrogram with image filtering ...
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0answers
590 views

calculating SNR from dbfs (using spectrograms)

I've the spectrogram of both noise and signal (both 5 seconds). Below image shows an example of the signal spectrogram: The colour of the spectrogram shows the intensity in dbfs (from 0 dbfs to -120 ...
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1answer
230 views

What is the spectrogram of an impulse response used for?

I saw that in acoustics an estimated impulse response of a room can be transformed using STFT/wavelets to a spectrogram as an analysis tool. However, I did not understand how the spectrogram is ...
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3answers
589 views

Why is the first axis of STFT frequency bin

When taking the STFT of an audio signal, the first axis is the frequency bins by convention, and the second axis is how it elapses through time. Is there a reason?
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1answer
914 views

Analysing mp3 quality with spectrum, how to interpret the results?

When comparing spectrum images between two different audio sources in order to determine which has better quality, I sometimes come to an impasse. For example, consider the following images from two ...
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3answers
5k views

Understanding overlapping in STFT

I understand the concept of the STFT. In order to avoid spectral leakage, you use a Hann window that overlaps by 50%. However, the problem that I have, is that the example code online does not account ...
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0answers
79 views

Values (amplitudes) of the CWT and their relationship to waveform amplitudes?

I'm coding up a scalogram in C++. Right now it calculates a single row of the CWT matrix and immediately maps it to a line of pixels. Trouble is my colouring scales with the values of the transform ...
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2answers
3k views

Wav To Spectrogram, Back To Wav

Currently, I'm writing a Python script, which should do the following: read an audio file respectively a wav file via scipy.io.wavfile.read(). calculate the spectrogram of given wav file. write the ...
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3answers
659 views

Guitar fundamental frequency vs pitch

When a note is played on the guitar, is the fundamental frequency always the strongest one or could a harmonic be the strongest one (in terms of amplitude). When could that happen? Also, when playing ...
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0answers
213 views

Help detecting target in pulsed radar signal

This signal is from the Pasternack $2.4\textrm{ GHz}$ development kit. The saved signal appears to be the pulsed waveform. It is sampled at $20\textrm{ kHz}$ for $4130$ points. I recorded a ...
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1answer
264 views

Do I need to bandpass filter the signal before applying the Zoom FFT algorithm?

Let's say I have an acoustic signal that I want to make a spectrogram of filled with broadband noise and tonals, sampled at oh, $44100\textrm{ kHz}$, and I want to zoom in on the band between $2600\...
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0answers
807 views

How does the size of a spectrogram relate to window length and frame rate?

I'm trying to understand the methodology from section 4 in this report about audio classification but I have some trouble understanding how they pre-process the data (dsp is not my area). $30$ ...
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2answers
416 views

Does an equivalent transformation of a signal to a spectrogram image exist in which the phase information is part of the resulting image?

I'm working on a research project where we would like to apply convolutional neural networks to an image representation of a signal. However, it seems that if I would use a spectrogram, I would end up ...
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0answers
484 views

removing noise from audio

I have an audio file, in the range of 4 kHz to 120 kHz. I want to remove the lines that are not harmonic and are recognized as environment noise. the energy of the signal in this interval for each ...
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2answers
466 views

Neural Network: Spectrogram Dimension

I like to work with a convolutional neural network in combination with a spectrogram as input. Assuming the spectrogram has the dimensions $T\times F$ (time$\times$frequency). Is it more natural to ...
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1answer
123 views

feature selection for classification for rare classes

I have a spectrogram of a signal and want to classify it. I used different features such as MFFC, the density of power spectrum and other common features and classify using the random forest, but I ...
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0answers
83 views

Epoching Data with no Events in mne?

I am new to Python and signal processsing, and I'm trying to create a spectrogram of EEG data taken during a course of general anesthesia. I would like to use MNE's ...
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0answers
155 views

difference between logged power spectrum and power spectrum?

What is the difference between a logged power spectrum and power spectrum... Well the log part. So can a normal power spectrum be converted to a logged power spectrum just by taking the log of the ...
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1answer
743 views

Comparing band-pass filters and convolutional kernels?

I am currently working on extracting features for speech recognition purposes. I wanted to try an approach similar to MFCC features in which the center frequency of each band pass filters are placed ...
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1answer
152 views

Extremely large reconstruction errors in NMF

First time in this stack... I am doing some audio analysis. I have a spectrogram ($N\approx 33000, M=1024$) and I need to run an NMF algorithm on it. I am using the Scikit learn implementation. And ...
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1answer
884 views

Reconstruction of audio signal from Spectrogram: Implementation

Is there somewhere an implementation available for the reconstruction of audio from a spectrogram? (e.g. based on this approach). I could not find anything, but I think there should be an ...
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0answers
315 views

Proper way of representing Static, delta, delta delta in a plot

I am currently working on recreating the result of this paper. The paper is about applying cnn in speech recognition, in which cnn is used to for feature extraction, for which a proper way of ...
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0answers
395 views

What is the autocorrelation equivalent of the spectrogram called?

I'm very knowledgeable about the differences between the Fourier transform, and the autocorrelation; mainly that one converts the time domain to the frequency domain, and the other finds periodicities ...
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1answer
125 views

Making a mesh out of the parameters from a STFT

I do not possess much knowledge about signal processing, so i hope to do a find an answer. I am reading a wav-file and then apply a fft on it. In theory, i think i have a 3 parameters i can use. Time ...
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1answer
2k views

What is the instantaneous frequency of this signal

Suppose we have the signal $x(t) = \cos(\pi t) + \cos(\pi t^2) + \cos(\pi \cos(\pi t))$ How can I find the formula which gives the instantaneous frequency $f(t)$?
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210 views

Normalize harmonics to the same fundamental frequency in a time series using MATLAB

I'm a bit new to DSP (so apologies if I get the terminology incorrect) and was wondering if the problem I have is standard. I have measured a time series of a fan and noticed that the my spectrogram ...
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1answer
372 views

Time-Frequency Analysis of Big Data - Data Size Reduction: averaging the most appropriate method?

Explanation: I would like to analyse the data from an experiment, which investigates the performance of a mechanical component using sensors, that has generated 2000 CSV files. Each file contains 513 ...
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1answer
324 views

Raw speech data into spectrogram

I am using Delphi trying to make a very simple speech recognition system. The system collects raw data well, but I have a hard time turning the data into a spectrogram: The system collects an array ...
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1answer
427 views

Digital Camera Spectroscopy?

Would it be possible to use a conventional Canon DSLR camera to do some kind of vaguely meaningful spectrum analysis with GNU Octave? My niece needs to do a biology science project for school so I ...
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1answer
308 views

Difference between spectrogram and a figure in an audio signal

i wrote a function in MATLAB which will divide a audio waveform (a speech) into smaller windows with overlap .The output will be a matrix X, each column of which contains the windows which i export. ...