# Questions tagged [noise]

In signal processing noise can be considered random unwanted data without meaning.

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### Does sum of random variables follows gaussian distribution although each have different mean and variances?

I understand Central limit theorem, but cannot understand the result when it applies to diverse situation. As far as I understand, Central limit theorem states follows: No matter what random variable ...
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### Stockwell S-Transform and multitapering

I want to estimate just the spectral amplitudes at different time points using S-transform given a noisy signal. Would I benefit (in terms of noise reduction) from an approach used in multi taper ...
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### Signal-to-Noise ratio of multivariate stochastic process from Correlation Matrix

I'm not in signal processing, I'm from an another discipline. I've derived a simple result which I presume must be well known in SP and I'd like to know whether there's a paper or textbook that has it ...
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### Concept of energy threshold

I am analyzing some program responsible for detecting the correct signal in the channel on the receiver side. It seems to me that such an implementation allows for the detection of the correct packets ...
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### Is it possible to remove the non-random noise in the signal by averaging?

Ex: We're measuring vibration Frequency response of a structure, and at the same time there is a constant source of vibration (noise) from a pump. The pump is exciting the structure by sinusoid ...
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### Recursive Least Square For Filtering

I just started doing research on Recursive Least Square for filtering noises such as sensors and dc motors noises. The only thing I've seen on the internet was Theoretical information about RLS but ...
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### Extracting ridges in automatically in image

I am trying to extract ridges from an image, calculated using the eigenvalues of the Hessian matrix (see answer in Best way of segmenting veins in leaves?). In this image I have zeroed out the ...
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### What kind of effect is this and what is it caused by?

In the screenshot below I have two audio signals. The upper one is the audio signal that is created with python and then played, whilst the lower one is the "same" signal but recorded via ...
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### What is the advantage of Wiener filter for noise reduction of a 1D signal?

I have a 1D signal, acquired by an accelerator sensor that measure the vibration of a structure. What is the advantage of using a Wiener filter for noise reduction compared to the other (more classic) ...
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### Wavelet denoising. Simple explanation

I am studying wavelet transform. In the matlab in the "wavemenu" package, I use "SWT denoising 1-D". I loaded my signal, performed a Haar 5 wavelet squelch. I got a good result. I ...
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### How can I add any kind of noise to image for a given SNR?

What is the best way to add any kind of noise (not only Gaussian noise) to 2D signal (image) for a given SNR?