Questions tagged [noise]

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

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How to calculate mean and Variance of Gaussian-distributed random noise?

I have been given a Gaussian-distributed random noise n(t) which has an average power of 5 mW. How can I calculate the mean and variance of noise n(t)? Any suggestions? Thanks!
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Adding noise in frequency domain while solving an SPDE

I’m implementing a numerical solver to a certain kind of a 2D stochastic PDE using Fourier Transforms. So, this solver is a Galerkin type method, which means that choosing the right basis functions I ...
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Adaptive removal of structured noise

I am trying to use a scanner with vertical banding. The scan head's black and white point calibration numbers have a modulation pattern on top of them. I am not sure if the calibration's banding is ...
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42 views

Comparing a clean, noisy and enhanced signal

I was doing some experiments on analyzing few audio samples and I'm stuck with this. Suppose we have a clean audio signal ($y_{clean}$), a noisy version of it ($y_{noisy}$) and an enhanced version ($...
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20 views

when exposure time is longer, the Poisson noise become Gaussian

Can we have an explanation of why exposure time is longer, the Poisson noise become Gaussian? Or any reference? Please provide a reference and I like to dig into more. Thanks in advance!!
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37 views

Finding optimal decision threshold for binary comm system

I'm trying to solve the following exercise: Given a system that transmits bit $b$ with probability $p_b$ and $-b$ with $p_{-b}$ and the transmission is degraded by AWGN $N(0,\sigma^2)$. What is the ...
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48 views

Adding noise to frequency response

I have the dynamics of a 2nd order system, mass-spring-damper for example, in the transfer-function format. For the analysis that I am doing, I am calculating the frequency response of the system by ...
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29 views

How to produce uniformly distributed low-frequency noise?

I want to design noise for the sake of modulation and it should have a frequency of under 1 Hz. This seems impossible to do for a frequency that low. Here is my Matlab script. The lowest frequency ...
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Are the SNR, Data Rate and Delay values correct in the below calculation?

I have these values: power_received_from_one_subcarrier = -80 dBm bandwidth_for_one_subcarrier = 180 KHz noise = -109 dBm When using {/, *}, the dBm values are ...
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1answer
46 views

Adding noise to real MRI data

I designed an algorithm for MRI data denoising which has good properties under heavy Rician noise (sigma is greater than 80). The method was tested on some phantoms and Rician noise generators. Now I ...
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Simulating Noise Variance in OFDM with MATLAB

I got a task to simulate an OFDM system. It works quite, but my problem is the calculation of the noise variance (and further noise for AWGN). Firstly, I'm calculating my noise variance in linear ...
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36 views

Removing white noise by taking the mean of many samples

I'm learning about signal processing, and I am attempting to remove white noise from an output of a blackbox system. As you can see from the above image (left is the input sin(t), right is the output)...
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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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40 views

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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47 views

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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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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50 views

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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34 views

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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27 views

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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1answer
54 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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547 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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41 views

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
30 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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106 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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31 views

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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23 views

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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12 views

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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57 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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3answers
423 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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35 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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46 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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736 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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144 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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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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