The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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.

Filter by
Sorted by
Tagged with
0
votes
0answers
132 views

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-...
0
votes
0answers
116 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 ...
0
votes
2answers
468 views
0
votes
0answers
76 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 ...
0
votes
1answer
396 views

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. ...
0
votes
2answers
219 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 ...
0
votes
1answer
40 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 ...
0
votes
0answers
168 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 ...
0
votes
0answers
23 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,...
-1
votes
1answer
37 views

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 ...
0
votes
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 ...
19
votes
4answers
21k 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 ...
1
vote
2answers
86 views

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 ...
1
vote
1answer
95 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 ...
0
votes
1answer
235 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: ...
5
votes
3answers
22k views

FFT to spectrum in decibel

Here is a 10 seconds-long 440hz sine wave normalized at $0\textrm{ dBFS}$. When computing the STFT (with the code below) of this audio file, I noticed that ...
1
vote
0answers
305 views

4 Hertz Modulation Energy

I am trying to distinguish between speech signals and music signals using feature extraction and SVM. I am looking for features to include for this purpose. While going through literature, I came ...
2
votes
2answers
137 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 ...
1
vote
1answer
490 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}(\...
1
vote
1answer
477 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 ...
0
votes
2answers
227 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 ...
0
votes
1answer
48 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: $$\...
0
votes
2answers
3k 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 ...
0
votes
1answer
644 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 ...
0
votes
0answers
140 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 ...
0
votes
1answer
175 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: ...
0
votes
1answer
206 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?
0
votes
1answer
85 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 ...
1
vote
1answer
4k 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 : ...
0
votes
0answers
244 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 ...
1
vote
1answer
143 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. ...
0
votes
2answers
291 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 ...
0
votes
1answer
402 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 ...
1
vote
1answer
259 views

Apply windowing before FFT or after?

I am computing a spectrogram and I've found a code example online which goes like this: ...
0
votes
1answer
186 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 ...
0
votes
2answers
171 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 ...
2
votes
0answers
174 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}^{\...
0
votes
1answer
70 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 ...
2
votes
1answer
228 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 ...
-1
votes
2answers
1k views

STFT computation

I'm trying to compute the STFT by my self. Thus, I wrote the following code: ...
4
votes
1answer
993 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 ...
0
votes
2answers
119 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 ...
0
votes
3answers
551 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 ...
-4
votes
2answers
61 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
0
votes
0answers
270 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 ...
2
votes
2answers
1k 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 ...
-1
votes
1answer
442 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 ...
2
votes
1answer
460 views

What are best practices to compute an audio spectrogram?

The spectrogram if generally defined with the squared magnitude of the fft. However, in lots of implementation, it seems that people just use the magnitude without square. Moreover an audio signal is ...
2
votes
1answer
187 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 ...
0
votes
3answers
493 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 ...