# Tagged Questions

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94 views

### A little bit better than this naive noise reduction

Given an audio signal x[n] sampled at 44.1khz (let's say 1 minute of music or speech) and a noise template noise[n] (let's say 2 ...
115 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 ...
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42 views

### Calculating Spectral Features on Stereo Audio Data (Centroid, Spread, Kurtosis etc.)?

I'm currently doing some MIR research with multi-tracks and want to make sure I am handling stereo audio correctly for the calculation of spectral features. For example, for things like getting the ...
82 views

### STFT Window Size is 2048, Why is the output 1025?

I feel like I am having a brainfart over here and can't seem to remember what's going on with STFT outputs. Consider these two lines of code from the Python library Librosa: ...
49 views

### Why is the name “Phase vocoder”?

I've read that phase vocoder is the STFT, but done in windows (i.e. using windowing). Why is it called "phase vocoder"?
91 views

### Principal Component Analysis as a step between STFT and MFCC

For computing Mel Frequency Cepstral Coefficients you can use already calculated STFTs as a basis and perform the Mel frequency mapping on it. My question: Does it make a significant difference if I ...
25 views

### Low-rank approximation of the STFT matrix : good audio compression technique?

I recently heard about this interesting math tool: With a matrix $A$, compute the SVD ($A = U \Sigma ^tV$ factorization, where $\Sigma$ is a diagonal matrix containing the "singular values") Keep ...
142 views

### How do I get the Time information after STFT?

I'm tring to code a STFT program in Matlab. I got results but I'm confused a bit. I have a audio signal of 900000 pts sampled at 1000Hz (15 min signal). I've taken fft with following parameters => ...
76 views

### Taking the Moving Average of STFT Results

I realize that this seems redundant, but I'm getting consistently better results when performing machine learning techniques that use spectral features extracted using the moving average process below,...
44 views

### Memory and bookkeeping for realtime window-overlap-add (WOLA)?

Given a realtime embedded system with input samples x(n) coming from an ADC, what is the pipeline to output y(n) if window-...
186 views

### Extreme audio stretching

This tool (Paul's Extreme Sound Stretch) is able to produce extreme timestrech (50x, or even 100000x). Any song can become an interesting sound texture or ambient music (listen to this example). The ...
34 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 ...
184 views

### Strange phase spectrum from stft

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

### Illustration of timed domain aliasing cancellation (TDAC, MDCT, lapped transform)

Can someone find or make a visual illustration of how time domain aliasing cancellation works in lapped transforms such as the MDCT? I think a graphic would make it a lot easier to understand, and I ...
21 views

### Are there condition numbers associated with the STFT, DWT?

Recently I learned that the DFT has good numerical stability since it can be represented as an orthogonal matrix, which has a condition number of 1. Is it possible to represent the STFT and DWT as ...
60 views

### Pesq numbers and clean speech comparison to processed speech

I am trying to evaluate my processed speech for my DSP project. My project is an implementation of an MMSE algorithm proposed by Y.Ephraim and D. Malah, "Speech Enhancement Using a Minimum Mean Square ...
545 views

### 'A priori' and 'a posteriori' SNR

I am reading this paper about speech enhancement using a minimum mean square error short time spectral amplitude estimator for our speech enhancement project. Basically in the paper they mix a clean ...
94 views

### Aliasing in the Short time Fourier Transform of a pulse

When attempting to take the Short Time Fourier Transform of a pulse, at the end of the pulse I'm running into problems. The signal looks like this at the end (it is a simple $sin^2$ pulse envelope, ...
1k views

### STFT: why overlapping the window?

For STFT, we impose window of certain size onto the original signal, then we perform fft on each window. The uncertanty about frequency and time is determined by the width of the window, however, I ...
94 views

### modified Bessel function for Speech enhancement Using MMSE in matlab

I am trying to implement an algorithm proposed in an old research paper by Ephraim and Malah for my DSP course project. I hope someone can help me with this difficult question. For the clean signal ...
87 views

### Variance of white noise and the STFT

I hope someone can help me understand the meaning of variance in this case. I am reading an old research paper by Ephraim and Malah (for my DSP project) and it says: Knowing that $D_k$ is the FFT ...
60 views

### Band-pass filtering on whole signal or overlapping chunks?

I am working with a signal acquired by a pulse oximeter, i.e. a device that records the change of light intensity reflected by a specific tissue depending on its blood perfusion. Since I am interest ...
74 views

### Interpreting magnitude of DFT results

I'm working on creating a simple program to render spectrograms like this one. In this plot, the X-axis is time, the Y-axis is frequency, and the color represents the magnitude of the DFT at that ...
118 views

### Implementing short-time Fourier transform

I have a $512$ sample frame, lets call it X. The frame is further divided into four sub-frames of $128$ samples each. Each of these sub-frames have a different ...
102 views

### Frequency and time marginals of STFT and Wigner-Ville Distribution

I want to compare time and frequency marginals of Wigner-Ville distribution and STFT. I can calculate WVD's marginals by simple sum operation since WVD is real. But I could not figure out how to deal ...
270 views

### how to read full input signal with STFT in matlab

Please help! I am trying to figure out why in the code i have below my input signal is being cropped but in the code I have a full signal created. The white noise created is 5000 samples for the right ...
499 views

### Onset Detection for Audio Signals

I am having a problem understanding how the author gets the onset envelope of an audio song in this paper. The entire section in question has been quoted below: First the input sound is resampled ...
579 views

### Computing narrowband spectrograms using MATLAB [closed]

I'm having an assignment of computing narrowband spectrograms using MATLAB. And I totally have no idea about the code. Can someone help me writing the code and explaining what's going on to me. Lots ...
286 views

### Audio compression with STFT

Let STFT[frame, freqbin] be the short-time Fourier transform of some audio data. (here frame is the index in time, and ...
51 views

### Matrix form of STFT

IS there a Matrix form of the STFT that could be applied to a signal directly, as in the case of DFT? We know the matrix structure of the DFT Matrix. Can we derive that somehow for a STFT Transform? ...
126 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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171 views

### PSD - Correct Formula for removing Noise

Ok, so finally some things are making sense. I'm trying to scale the results, which I have done by the following equation:  PS_{rms} = \frac{2 \cdot \left |y _{...
89 views

### STFT - Putting it all together

I'm currently reading this paper: http://www.rssd.esa.int/SP/LISAPATHFINDER/docs/Data_Analysis/GH_FFT.pdf On page 21, it has a section called "Putting it all together", it states the following steps:...