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1answer
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 ...
-2
votes
3answers
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 ...
0
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0answers
26 views

Real-time STFT masking

When doing offline audio processing (example : template-based noise reduction) I can use this classic method : $$\boxed{\textrm{Input}}\longrightarrow\boxed{\textrm{STFT matrix}}\longrightarrow \...
1
vote
1answer
19 views

What is first order difference?

I don't understand what is a first order sequence. For more context: I am reading a paper where the author extracts different sequences (in the STFT domain) and then "The resulting sequences are ...
0
votes
1answer
46 views

How do I measure frequency of an audio file into an array?

So I know how to plot fft the audio file within Matlab and a window pops up. My question is, what next? I want to know how to go about measuring the frequency(s). I have two similar audio files, of ...
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0answers
15 views

How can i plot the power spectrum in terms of time history representation of a signal?

I have a signal and How to plot the power spectrum in terms of time history representation as shown in the below figure in MATLAB. and also i would like to plot the spectrogram as shown in the ...
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0answers
56 views

STFT on audio signal

I am trying to implement a STFT on audio signal as an exercise, and in order to do real-time filtering if I can get the "sound->STFT->inverseSTFT->reconstructed sound" chain to work. What I do for ...
3
votes
1answer
92 views

Recovering phase from spectrogram

In this answer, an iterative algorithm is given for recovering a signal from its spectrogram, assuming overlapping windows: $$ x_{n+1} = \operatorname{istft}(S \cdot \exp(i \cdot \operatorname{angle}(...
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0answers
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 ...
4
votes
1answer
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: ...
0
votes
1answer
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"?
0
votes
1answer
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 ...
2
votes
0answers
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 ...
0
votes
2answers
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 => ...
1
vote
1answer
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,...
0
votes
0answers
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-...
0
votes
3answers
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 ...
0
votes
1answer
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 ...
0
votes
1answer
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: ...
2
votes
0answers
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 ...
0
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0answers
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 ...
0
votes
1answer
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 ...
0
votes
2answers
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 ...
3
votes
0answers
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, ...
2
votes
1answer
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 ...
0
votes
1answer
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 ...
0
votes
1answer
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 ...
0
votes
0answers
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 ...
0
votes
1answer
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 ...
-1
votes
2answers
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 ...
0
votes
0answers
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 ...
-1
votes
1answer
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 ...
2
votes
1answer
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 ...
1
vote
1answer
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 ...
0
votes
2answers
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 ...
0
votes
1answer
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? ...
0
votes
1answer
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 ...
1
vote
0answers
56 views

Frequency contour cross-correlation

I'm trying to segment (or extract) different calls from a spectrogram. My current method, calculates a threshold value (variance) and then using RMS can detect voiced/unvoiced signals: $$ Thres = (1 -...
0
votes
0answers
39 views

Time of sound-signal

Let's say I have a sound file, I then compute the Spectrogram and segment each part of it. Assume that it is a recording of someone saying the word "Hello" and therefore, each piece is given like so: ...
0
votes
0answers
72 views

Calculating hertz / kHz

Over the past few weeks, I have been working on a problem of segmenting an audio file containing some bat samples. I have now successfully come up with a moderate algorithm to do this. I am trying ...
-1
votes
1answer
51 views

Which FIR filter should I choose?

If I have the following spectrogram: And only wanted to have the signals that are in a particular frequency range (2627 - 3939htz).. Can I run a FIR filter to only allow these signals through, and ...
-1
votes
2answers
132 views

Suggested algorithms for detecting voiced / unvoiced signals [duplicate]

Right. I'm trying to understand the concepts for determining where the signal contains voiced and unvoiced parts. I have created a spectrogram (STFT) of a signal and I'm trying to separate from ...
-1
votes
1answer
141 views

STFT Time Variance - Threshold

This is a follow up question to: Segment/Idenfication of signal from a spectrogram My main goal is to identify (segment) all of the calls from a given signal. The signal looks like the following (...
2
votes
0answers
109 views

Segment/Idenfication of signal from a spectrogram

I have the following Spectrogram of a signal: Essentially, in this signal, I know there is one point of interest (between 60-80) and between the the particular frequencies. I could, potentially ...
0
votes
2answers
325 views

Normalizing a spectrogram or a pitch class profile

I am developing a chord recognition program using neural networks.I need to normalize the spectrogram or my pitch class profile to provide inputs for the neural network. The pitch class profile ...
1
vote
1answer
574 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 | ...
2
votes
1answer
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 _{...
1
vote
2answers
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:...
0
votes
1answer
54 views

phenomenon when window size for STFT is too short

Hi I was researching on STFT when I encountered this slide online I don't understand the points, Can anyone explain them? Thanks in advance.
2
votes
1answer
321 views

PSD - Spectrum analysis

Could someone tell me where it is that I might be going wrong with the following problem? Ok, so I'm computing a spectrogram, and, trying to return the PDS of the signal (to show where the signal ...