# Tag Info

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### FFT to spectrum in decibel

Definitely you will have to calibrate your system. You need to know what is the relationship between dBFS (Decibel Full-Scale) and dB scale you want to measure. In case of digital microphones, you ...
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### STFT: why overlapping the window?

We always want to apply some kind of a window function in order to minimize the effect of leakage. This makes rectangular window (lack of any windowing) case never used, this is why: Any tapering ...
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### Advantage of STFT over wavelet transform

Wavelet transforms and short-term/short-time Fourier transforms are broad names for classes of transformations that are not totally distinct and may overlap (pun intended). Both can be efficient for ...

### What is first order difference?

The first-order difference operation is a technique for numerical differentiation. It is the simplest method that I know of, and consists of just treating a discrete-time signal as piecewise linear ...
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### STFT amplitude normalization, librosa library

I did answer a similar question a few years back, but can't find it. Basically, you are losing the energy because of the windowing. It's true to say that you should multiply the spectra by 2 in order ...

### STFT and DWT (Wavelets)

The short-time Fourier transform is generally a redundant transformation, usually implemented with the same subsampling over every frequency. If the window is well chosen, it is complete: you can ...

### FFT to spectrum in decibel

Some details to Jojek's post. Shared here for future reference. The key is to take the window in consideration and taking a reference ref which corresponds to ...

### 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%. I'm sorry but you have a misunderstanding of spectral leakage in addition to how ...

### Signal processing techniques for an accelerometer signal?

I'm wondering why the STFT pops out. To me, wouldn't a simple threshold on the signal itself or on its envelope do better / just as well, after removal of the g ...

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

The continuous Fourier transform possesses symmetries when computed on real signals (Hermitian symmetry). The discrete version, an FFT (of even length) possesses a slighty twisted symmetry. The DC ...
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### Approximation of Hilbert Transform Using Very Short Hilbert Transform FIR / IIR Filter

This is more like an extended comment to chart the possible answers. Hilbert transform is a frequency domain 90-degree phase shift of the signal. It has an antisymmetrical impulse response around ...
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### Could not construct original matrix using SVD

Don't have enough reputation to comment but you need to use the conjugate transpose in your formula for the result to be correct. So try stftb=U*S*V'; in the last ...

### Choosing the right overlap for a window function

I tried my best but I couldn't find a resource that would list the "good" overlap factors for common and less common windows. Here's a list of window functions and overlap factors that have constant ...
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### Meaning of Hop-Size in Filter Bank Interpretation of Short Term Fourier Transform

Your message was apparently unfinished ('When reading about the DCT...'). I thus will be starting from it. The JPEG compression format is an example of hopping. A DCT-filter bank (Discrete Cosine ...

### What do I lose when I set overlap rate to a really high value in STFT

If you don’t care about computational costs, you can start a window at each sample (e.g. 100% - 1 sample overlap). It’s well into diminishing returns, but phase vocoder estimation methods work ...
There are several ways. Start with taking the iFFT of $S^{(1)}$ and $S^{(2)}$. Let's call the results $m^{(1)}$ and $m^{(2)}$, since they are modified. They are back in the time domain and ...
In general, if you have complex spectrum and need PSD in dB the mathematical equation is $$P_{xx} = 20\cdot\log_{10}|X_{x}|,$$ where $P_{xx}$ is your PSD in dB and $X_{x}$ is your complex STFT ...