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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Frequency range of acoustic feedback

What is the frequency range in which acoustic feedback can be found? Most importantly, is there some lowest frequency below which one can expect not to find any feedback? My conclusion from the ...
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39 views

Why does the specgram of this simple sine wave look strange?

I'm trying to test some intuition using the matplotlib specgram routine. I first generate a simple sine wave ...
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1answer
26 views

could not constract original matrix with matlab svd's function

I need to read a .wav file, make a 2D matrix from it using stft, generate singular value decomposition of it using svd method and do some watermarkings... but I can't build the original matrix again ...
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57 views

Extracting original signal from overlapping area

Considering this image, where I have a spectral decomposition of a light bulb. Due to the non point shaped light source, the spectral decomposition using a diffraction grating in front of my camera ...
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16 views

STFT multiplied with Gaussian Impulse vs STFT multiplied by unit height rectangular impulse

I am currently analysing my signal by looking at its spectrogram to determine the sinusoidal frequency content at the local sections of my signal overtime. I can do my spectrogram in 2 ways: ...
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19 views

Simulate noise on the x axis for raw time-of-flight mass spectrometry signals

I am analyzing raw mass spectra produced by a time-of-flight mass spectrometer. These spectra are 2 dimensional signals that consist in intensity values with respect to mass/charge values. Here is an ...
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3answers
79 views

Drawing a Spectrogram off of FFT - what are the decibels relative to?

I am trying to draw a spectrogram from FFT data I get from audio files. The problem is that I can't figure out is what the yielded power (decibels) are relative to. I'm getting some arbitrary ...
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25 views

Spectral Smoothing via Cepstrum

I have been trying to do something that I thought was very simple, and failing terribly: I have been trying to smooth the spectrum of a frame of audio, by transforming into the cepstral domain and ...
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43 views

Are there any pictures of a sample accurate spectrogram on the web or in books?

I programmed a sample accurate spectrogram some time ago and i still have never seen a picture of another one. It's interesting maths, i was told it's trivial, so why has no one else posted research ...
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209 views

What is the most precise frequency analysis spectrography algorythm?

Everyone uses Fast Fourier Transform, which is fast at the detriment of precision. The input audio has sample accuracy and the FFT has 1/64 sample accuracy. What algorithms can output high resolution ...
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48 views

Matlab: is a highpass filter what I want, to obtain my required spectrogram? How do I design/apply this? (pic included)

The axes are wrong in the spectrogram. I have an audio wav file, and I know the sampling rate. this is read into the audioData variable. The audio is 1 channel. selected window length I believe (can't ...
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61 views

How does we choose parameter in SPECTROGRAM(X,WINDOW,NOVERLAP,NFFT,Fs)

I am facing problem in SPECTROGRAM(X,WINDOW,NOVERLAP,NFFT,Fs) How would i choose Window, Noverlap,nfft parameter for spectrogram of children voices sampled at ...
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89 views

Converting musicg spectrogram output to dBFS

I'm trying to convert musicg Spectrogram output to dBFS. With 16-bit signed integer PCM audio, and an FFT length of 2048, I'm trying to analyze the spectrogram for an audio file to determine things ...
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1answer
88 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
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2answers
121 views

Spectrogram of a chirp and its FFT

This question follows from an answer to this other question: Conceptual question on FFT and chirp signal I wrote a code starting from the spectrogram to compare it with the FFT result. ...
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1answer
45 views

Developing a classifier for a periodic music

I am trying to develop a classifier for Indian Taals, for which I would be focusing only on the Tabla. Now once a extract a period of the Tala(a repetitive pattern), I want to develop some feature ...
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84 views

Choosing the best measure for machine learning on a Spectrogram

I am working on an application to classify Talas(a piece of music with onsets). For that, I have the spectrogram of a Tala, which I want to compare with the test Tala, or compare 2 Talas. For this I ...
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1answer
399 views

Reconstructing time domain signal with Hanning window

I am currently working on a frequency domain real-time application on a digital signal processor. Currently for one time frame of my algorithm I read in time domain data into a buffer, perform a ...
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30 views

Can uneven sampled points generate valid PSD and spectrogram?

My recording device samples signal at 100 Hz. At each sampling point, it generates 512 values (I assume due to non-ideal impulse in practice, so each impulse is actually a window with certain width ...
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154 views

Rendering a spectrogram of audio data - resulting magnitudes are all too close together

I'm working on creating an application which will render a spectrogram of the audio in an MP3 file. I'm having some trouble, though - after running the audio samples through my program, the resulting ...
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80 views

Looking for an algorithm that computes weighted average of frequencies intensity from narrow band in spectrograph

I am searching for the algorithm that takes (audio) signal as an input and outputs weighted intensity of the frequencies of some narrow band (axis X) in time (axis Y). Frequency in the middle of that ...
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1answer
48 views

Frequency resolution

I have made a stft_func in MATLAB which takes window length i.e t_short as a parameter for window length. Now, this function is ...
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1answer
61 views

Given a spectrogram, how do I calculate loudness over time?

I want to calculate the loudness of a given sound over time (like, in a graph) from its spectrogram. Can I do this from the spectrogram or is it better to do from the raw sound?
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195 views

Improve spectrogram appearance using windowing functions MATLAB

I have a program which plots data obtained in a NI USB DAQ realtime to a spectrogram plot using the surf function. I'd like to improve the appearance of the plot using some sort of windowing function. ...
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71 views

Understanding PCA

OK, I have tried to ask the same question in the math site on stack exchange but no real joy. Apologises I'd this is the wrong forum. I am trying to compute the PCA of a spectrogram.. It is 486x128 ...
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1answer
73 views

Detecting a curve with certain characteristics in a spectrogram

I have a spectrogram built by breaking a signal into chunks and taking the FFT of these chunks. An example spectrogram is: In this spectrogram I am looking for a curve (aka pitch contour) that: ...
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93 views

How to obtain the Spectrogram of a signal

I am trying to use Matlab to compute the spectrogram of a signal but I can't seem to figure out how Matlab computes the spectrogram.Consider the case where I have a ...
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1answer
371 views

PSD - Is this formula correct?

Trying to understand whether or not I am calculating the PSD correctly. Below is the equation that I am using: $$ PSD_{rms}(f_{m} = m \cdot f_{res}) = \frac{PS_{rms} }{ENBW} = \frac{2 \cdot \left | ...
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314 views

Spectrogram - Am I missing something?

I have the following signal: I'm trying to compute a Spectrogram algorithm, but, don't think I'm doing it right.. I have computed the following: 1) STFT (size 256 with an overlap of 128) 2) ...
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143 views

Will the resulting spectrogram from this algorithm be 1D or 2D?

I'm implementing a spectrogram algorithm and I get the basic concepts, however, I'm struggling with something. Let's say I have a 1D vector: ...
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3answers
500 views

Why do we get ripples in the frequency spectrum of a chirp, and how do I remove it?

The ripples in the amplitude spectrum of a linear spectrum is undesirable. I desire to obtain a flat spectrum response. Hence, how can I remove these ripples? Also, which factors (like time bandwidth ...
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1k views

Get spectrogram matrix without specgram in MatLab

I have a signal in Malab, and I need a matrix, probably transposed specgram matrix without using specgram tool. Is it possible?
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1k views

interpret wavelet scalogram

My knowledge of wavelets is less than epsilon. Bear with me. If I have a signal of two well separated sinusoids (15 and 48 Hz) plus some random noise, I can clearly make out the two in a spectrogram ...
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99 views

STFT computational burden

I have a signal with length of $N$. The sampling frequency is $f_s$. Window size is $w$ The noverlap size is set to $m$. And $nfft$ is selected for frequency resolutions. I am running a STFT with ...
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2k views

How can I compute a time-frequency cross-spectrum in MATLAB?

MATLAB has a spectrogram function for the time-frequency analysis of a single signal. It also has a cpsd function for estimating the cross-frequency spectrum for two signals. However, cpsd averages ...
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167 views

I can't figure out why spectral features are “displaced” on a spectrogram

I'm trying to create a spectrogram of a complex signal 'y', but I'm running into a problem where the spectrogram that I create appears to have its spectral features "displaced" in frequency space, and ...
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3answers
402 views

strange phenomenon in spectrogram of Windowed Fourier Transform [edited] [closed]

I am trying to understand how the Windowed Fourier transform works, so I used Matlab to create an artificial signal, and plotted the Windowed Fourier transform using a gaussian window. $x(t) = ...
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342 views

Spectrogram from Complex Morlet wavelet ( recreating article result from data)

I am trying to recreate the following results: ...from the following data: Dropbox Link (FS40.dat) The time is in milliseconds (frequency is 40000 Hz) The article state that they used Complex ...
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1answer
126 views

What information is lost, if any, in normalizing Seismic/Earthquake time-frames in an STFT to equal variance?

This might be more of a statistical question, but let us assume that we take a spectrogram, or STFT, where time is on the x-axis, and frequency is on the y-axis in this matrix. What information might ...
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5answers
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generating spectrograms in python with less noise

I'm trying to do something similar to Shazam (paper here) in Python. Basically the idea is to use FFT with sliding window to transform both WAV files and recorded audio to the same spectral ...
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1answer
219 views

Gammatone filter vs 2D FFT for spectograms

I am working on speech segeration and each source I am reading , spectograms are being made by filterbanks which uses gammatone filters . I can't find a proper c++ source code which would make me ...
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2answers
123 views

Estimating noise level without 'quiet' segment

I have a signal which consists of an onset and a release period. The onset, sounding like a thud, excites frequencies across the entire frequency range (0-22 kHz). It lasts for about 0.1 s. The ...
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1answer
1k views

Spectrogram of wav file

I am calculating spectrogram of a audio file of 36 second using the following code snippet: ...
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1answer
258 views

Converting mel spectrogram to Spectrogram

I have a set of songs for which I extracted the STFT (Short Time Fourier Transform) and used the magnitude spectrum $|S|$ to calculate the mel spectrogram by using a mel filterbank matrix $M$, so ...
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1answer
95 views

Phoneme Clustering

My aim is to find cluster phonemes from a wav file. I would like to go through the following steps: I am calculating spectrogram. Calculate energy of each frame. Cluster the frames using k-means ...
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3answers
3k views

Reconstruction of audio signal from Spectrogram

I have a set of songs for which I extracted the magnitude spectrogram using a Hamming Window with 50% overlap. After extracting the spectrogram, I did some dimensionality reduction using Principal ...
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1answer
1k views

Applying FFT to PCM stream

I would like to use a .WAV file and convert it into a spectogram. Any idea how to do this with Naudio? Basically the flow should be like this, I think: Convert WAV file to PCM stream Convert PCM ...
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565 views

Programming language for sound manipulation [closed]

Having had little experience in PHP, I moved to C++ in-order to create a spectrogram, I wanted to create probably the simplest/easiest one for my first project, so easy infact I don't need ...
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What is the theoretic difference in the ways to compute the spectrogram?

I have noticed that the spectrogram for a audio signal is often calculated in different ways when the result from the DFT is transformed into real numbers; some tend to compute $|k|$ or $|k|^2$ while ...
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Points of interest in a spectrogram

We have several audio tracks, all of which are different versions of the same track under one type of distortion: the speed of the track is increased by a constant factor K (hence frequences are ...