Questions tagged [noise]

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

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77 views

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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76 views

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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51 views

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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1answer
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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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2answers
53 views

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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SNR of filter output

I have a filter where the input is: $$ x(t) = s(t) + w(t) $$ which is signal plus white Gaussian noise and the output is $y(t)$. If the impulse response of the filter is $h(t)$, then: $$y(t) = s(t)*h(...
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Is it possible to add some kind of noise to a non stationary (having unit root) signals to make them stationary?

I am working on time-series signals for which I need to fit a model (like MVAR) that could describe the process satisfactorily. However, my signal has a unit root and is highly non-stationary because ...
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Allan variance vs power spectrum density for noise estimation

I know than we can estimate noise level (and noise colors) from power spectrum density function OR from Allan variance. Why do we need Allan variance at all for such estimation? In my opinion PSD ...
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Noise removal where gains are >1

I am currently working on some noise removal algorithms and have come across what seems to be an oversight in the design of some of these algorithms. Two of the algorithms I am looking at use the PSD ...
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52 views

Spectral Property of Bandlimited Quantized Signal

recently I meet a problem. I generate a random Gaussian signal $x$ with mean $0$ in MATLAB. And use a $4$th lowpass Butterworth filter to acquire $x'$. Then I use the binary rounding quantization ...
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Is there any modern information about a 12-hour periodicity in sonar noise?

I have a copy of Principles of underwater sound by Urick, 3rd edition. In the chapter on The noise background of the sea: ambient noise level, on pages 215/216, it says "The analysis of data in ...
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1answer
545 views

Why removing noise increases my audio file size?

I took some mp3 files of people talk with noise in the background and then removed the background noise using online voice seperator tools (such as https://vocalremover.org/). I was surprised to find ...
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What is the frequency of the Gaussian white noise model in control systems?

The design of control systems, particularly for SISO systems, is made convenient by tools such as Bode plots and the corresponding Nyquist stability criterion. These concepts allow engineers to design ...
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Average identical sweeps or lowpass filter sweeps first?

There are 5-10 replicate sweeps of measurements that are meant to be averaged. I also typically lowpass filter the signal at 2000Hz. The target signals are in the 0-100Hz range, and have, for lack of ...
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1answer
29 views

Variance of filtered white noise

I was asked a question, as posted here, and the answer given is (A) i.e. $\frac{3}{2} A^2 N_0$. My solution steps was: Finding the mean of the output process: Since input is gaussian the output will ...
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1answer
87 views

Variance of Integral of a real white Gaussian Noise Process

In this question, is the answer not equal to infinity ? Answer is mentioned as 6. But my doubt is cant we think of it like a linear combination of many independent random variables each having ...
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Why does my calculated SNR have so much variance?

I am running a SNR test for a real system as part of a final system test. There is real noise. The noise is calculated as the ratio between two measurements. I noticed however that my SNR value is ...
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27 views

Calculating SNR of RF Waveform

I am trying to calculate the signal to noise ratio of this signal. I'm aware that the SNR calculation should be $$SNR_{db} = 10\log_{10}\frac{P_s}{P_n}$$ For the noise signal $w[n]$ I'm using the ...
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translating 1 dB increase in thermal noise to interference to noise ratio (I/N)

I often see statements like "1 dB increase in the receiver thermal noise density results in an interference-to-noise density ratio of -6 dB". How can I obtain this result mathematically? ...
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Calculating the variance of vibration acceleration

In a vibration measurement of a rotating blade, I have the following information. The vibration signal is measured using a ICP accelerometer which has the following specification Measurement range: ...
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After upscaling a signal what noise metric to use for noise qualification

If I have a 2d signal (like image) and interpolate (linear) it to get an upsampled signal, how can I qualify the noise, with which metric? STD changes between the signal and its'upsampled counterpart ...
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52 views

White noise generation for different bandwidth signals in MATLAB

I'm working on simulating an uplink scenario in satellite communication. The goal is to send a preamble + data to the satellite from ground station. Data symbols have a bandwidth of $15\ \rm kHz$ and ...
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standard deviation of two constant noised signals related through interpolation

Let us say say we have a noised constant signal and want to evaluate the standard deviation (std) of the noise. We calculate the std of the said noised signal and call it $\sigma_1$. Now we process ...
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331 views

White Gaussian Noise Spectrum and Power

White Gaussian noise has constant power spectral density $N_0/2$. I know that the area under the power spectral density curve between two points gives the power of the signal between these two points. ...
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34 views

Deconvolution with noisy measurement of impulse response function

I observe a noisy 1D signal that has passed through some linear time-invariant filter: $$z(t) = (h\star x)(t) + n(t)$$ where $h(t)$ is the filter, and I am hoping to recover $x(t)$. $n(t)$ is some ...
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Thresholding algorithm for separating skin from clothes in python

I have an several images that look like the following: I would like to separate the skin from the trousers here without specifically training a segmentation model. Can anyone suggest any such ...
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44 views

How to remove noise from frequency spectrum?

I have a signal acquired at 40 MHz sampling rate, from an ultrasound transducer with center frequency of 5 MHz. The frequency spectrum is shown in attached images (whole spectrum and zoomed). There is ...
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23 views

Dark current rate using Matlab

I have darkcurrentrate (Dark noise) data collected at various ISO speeds such as ISO 55, ISO 99, ISO 198 etc. and the files are in .dng format. Can someone suggest how to calculate the dark current ...
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What types of distributions (except the Gaussian) that follow for random jitter in a correlated signal?

For the simple case, let's consider the correlated signal $s$ with jitter (without noise) as follows: \begin{align} s(t, \theta_i) = \cos(2\pi f (t + \epsilon_t) + \phi + \theta_i), ~~ i=0,1, ... \end{...
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1answer
35 views

White gaussian noise analysis deduction

I´m stuck in a deduction analysis of the variance of a gaussian white noise signal in a "integrate-and-dump detector" of a baseband data transmission receiver, where $n(t)$ is white noise ...
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3answers
102 views

Noise added to a Random Process

if we have a discrete random process \begin{equation} x\left(n\right)\:=\:0.2x\left(n-1\right)+w\left(n\right)+w\left(n-1\right) \end{equation} where $ w\left(n\right)$ is a noise with a mean $ m_w=0....
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1answer
405 views

Difference between double-sided and single-sided AWGN noise after bandpass filtering?

Consider a bandpass signal $s(t)$ with bandwidth $W$. After bandpass filtering, let the output signal be $r(t)=s(t)+n(t)$ I have read a paper that denotes $n(t)$ as Gaussian noise with one-sided power ...
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109 views

Averaging data from 2 sensors

Suppose we take a reading of a single rotating axis using 2 identical sensors. Intuitively, I think that averaging the outputs of both sensors will yield a less noisy result. But what if sensor A has ...
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2answers
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How to detect defects at a contour?

I am detecting a contour of a smooth metal. I do binarization first then use openCV contour function. But sometimes the metal has defects such as dots or dusts at edge. This leads a unsmooth edge. Is ...
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69 views

Given a -3dB/ octave filter that makes Pink Noise, how can I make a +3dB/ octave filter that makes Blue/ Azure Noise?

I learnt from here that the following filter can turn white noise into pink (-3dB/ octave). ...
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Seeking advice on how to denoise a video from poor CCTV lighting

I have grainy CCTV footage that will need some amount of clean up. I request for ideas on the best way to clean out the noise. I am attaching a frame extracted from the video here for hints on the ...
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1answer
59 views

Why do I keep seeing this equation for $E_b/N_0$

I keep seeing $$\frac{E_b}{N_0} = \frac{E_\text{s}}{\rho N_0}; ~~ \rho=\log_2{M}$$ But my own calculation is: $$\frac{E_b}{N_0} = \frac{E_s}{N_0}\frac{1}{k}$$ Where $k = \frac{\rho n}{ms}$, where $\...
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Removal of parallel-line like streaks

Just wondering what image processing techniques can remove some artifacts of parallel-line like streaks, which are shown in the red box in the above picture. I was thinking about removing it from ...
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1answer
59 views

Noise removal in discrete signal

How do i remove these kinds of noise from the discrete signal in python?
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586 views

Increasing SNR and Dynamic Range using Oversampling

How much gain in dynamic range and SNR can be expected if we are to oversample a signal with fixed analog input bandwidth. For Example if I have a analog filter at the input which limits the bandwidth ...
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1answer
111 views

How is signal to noise ratio actually measured by receiver equipment?

This sounds like quite a basic question but it surprised me, how is SNR actually measured? You have the incoming signal: It seems like the SNR is just the visual comparison of the peak signal '...
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2answers
81 views

Determine the Signal Curve from Parameters of a Power Curve by Noisy Measurement

I have a class of signals described by function: $$ f(inc,d,t)=inc\cdot t^d $$ where inc and d have a finite set of values like 1, 2, 3, i.e. $$ inc, d\in \left \{1,2,3 \right \} $$ and $$ 0\leq t<...
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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?
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167 views

Additive noise meaning

What is additive noise? What actually additive means? I have tried to search in the internet but the only answer that I get is the noises gets added therefore it is additive, which make me think that ...
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Colored noise and adjusting covariance matrix with change of frequency

Assume a signal sampled at 2Hz. Assume it is a colored noise with known PSD. The measurement equation to be used in a Kalman filter requires a covariance matrix. If I want to sample at 9Hz (for ...

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