Questions tagged [noise]

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

245 questions with no upvoted or accepted answers
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56 views

Minimum statistics noise estimate - how to calculate the underestimation factor?

I have implemented a basic noise estimator using the minimum statistics method. Noise power estimate is obtained as a minimum of the short time power estimate within a window of subband power samples. ...
5
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0answers
1k views

detect what is noise in audio signal

I'm trying to filter noise from an audio signal. The signal was and is going to be recorded in a city environment which always contains some white/pink noise. At this moment I'm using two options to ...
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0answers
119 views

Relative beat detection for two audio recordings

I'm trying to synchronize (overlap) two audio recordings of the same song: a complete HQ version, and an incomplete, noisy version (phone recording for example). The noisy recording may have had its ...
3
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2answers
418 views

Why is the relationship between Es/N0 and SNR different for complex and real signals?

I try to use the AWGN Channel model of MATLAB to build my simulation model, but the explanation of the relationship between Es/N0 and SNR in the official manual of MATLAB makes me confused. It says ...
3
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0answers
593 views

frequency spectrum of a sampled signal, PSD and power discussion

Before I go into my question, I first want to review the basics of sampling a signal and at the same time I build the basics of my questions so that they make more sense. I know I have asked couple of ...
3
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0answers
109 views

Energy Detection in Presence of Colored Gaussian Noise

Before asking my question, let me introduce the context: For spectrum sensing based on energy detection, which has been widely studied in presence of AWGN, the optimal detection threshold is computed ...
3
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0answers
342 views

Remove the extra peaks by lag

Suppose that we have some peaks of a signal and we know the time lag between dominant peaks. How is it possible to remove the extra peaks by applying time lag ? Lets say it in MATLAB ...
3
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0answers
1k views

Why PSNR decreases for Ultrasound Images?

I am working different types of filters to remove speckle noise in ultrasound image. I have taken the below paper as my base paper and trying to reproduce the results of this paper: My Base Paper I ...
3
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1answer
2k views

Calculation of an autocorrelation function

A sample of a random process is given as: $$ x(t) = A\cos(2\pi f_0t) + Bw(t) $$ where $w(t)$ is a white noise process with $0$ mean and a power spectral density of $\frac{N_0}{2}$, and $f_0$, $A$ ...
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0answers
57 views

Black dots in spectrogram

Whenever I zoom in on the spectrogram of a recording I made with my phone I see these strange dark dots, unfortunately I cannot try another phone. What is causing them? They seem randomly distributed ...
2
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0answers
40 views

Estimating shot noise - what's the origin?

If I have some photon detector, say a CCD, how do I estimate the error introduced by shot noise correctly? Typically, sources found on the internet say that the shot noise is the square root of the ...
2
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1answer
45 views

A filter removing forbidden information in the stop-band

Is it possible, and how could it be done, to make an extension of filters that converts the signal in the filter's stop-band into noise with no information content or at least with zero correlation to ...
2
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1answer
100 views

What is the variance of DFT of Fourier coefficient of difference of a vector of white noise?

Consider $\big\{x[0], x[1], \ldots, x[N-1]\big\}$. Suppose, \begin{cases} x[n] \sim \mathcal N\left(0, \sigma^2\right)\\ \big\langle x[n], x[n-1]\big\rangle = \frac12 & \forall \ n\\ \big\langle x[...
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0answers
97 views

How to find the noise power in my simulation

I am currently working a tricky communication chain that I want to simulate into Matlab. The chain is like a classic BPSK modulator/demodulator chain, but where the BPSK modulated signal has been ...
2
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1answer
206 views

Meaning of AWGN complex and real noise under BPSK Decision Scheme

I'm currently studying error correcting codes and decided to replicate some common Bit Error Rate curves under BPSK modulation. I initially had trouble to convert SNR to a Gaussian $\sigma$ because I ...
2
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1answer
135 views

How to describe correlated noise after the signal is oversampled?

The Gaussian noise in discrete signal models is usually assumed to be independent and identically distributed variables (i.i.d.). Does this mean that the signal must be sampled with the sampling rate ...
2
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0answers
33 views

Local noise intensity in an image

Noise can be assessed in uniform regions of an image, by subtracting a lowpass-filtered version of it. Then from the histogram of intensities, a global measure can be obtained (such as the average ...
2
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1answer
228 views

White noise generation in frequency domain (stfft) produces a periodic pattern

I have created a set of spectral processing modules for SynthEdit next to be released, implenting short time fft, so I am now quite experienced with the matter, but recently encounteted an unexpected ...
2
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0answers
45 views

How to remove varying noise from strain data in MATLAB

I'm very new to signal processing. I have some data measured over time at 800 Hz. I'm interested in the high frequency signals. You can easily identify them in the image below (in this case, 3 signals)...
2
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1answer
340 views

Why I don't get the right PSD

I need to model a noise with a given PSD. To do this, I am starting from a white gaussian noise (WGN) and feed with the WGN a transfer function, which will act like a filter. In fact,it's easy to ...
2
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1answer
63 views

BER performance of fractional equalizers for colored noise

I am trying to compare the BER performance of fractional and symbol spaced equalizers for channel equalization in colored noise scenario. I have found from simulation that for positively correlated ...
2
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1answer
95 views

Evaluation of Jacobian for Extended Kalman Filter

For the non-additive noise case, \begin{equation} x_k = f(x_{k-1}, u_{k-1}, \xi_{k-1}) \\ y_k = h(x_k, \nu_k) \end{equation} the EKF takes into account the jacobian wrt to the noise terms $ L_{k-1} =...
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72 views

Phase noise definition

I have some problem with understanding the phase noise definition formula. please see this image: I can't understand the paragraph that I show ? near it. How is it possible to get phase noise > 0 ...
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0answers
71 views

Detection over AWGN analysis disagrees with Monte Carlo simulation

I have a fixed vector $\mathbf{s} \in \{\pm1\}^m$ and a random vector $\mathbf{d} \in \{\pm1\}^m$. I send either $\mathbf{x} = \mathbf{x_1} = [\mathbf{s}\space\mathbf{d}]$ or $\mathbf{x} = \mathbf{...
2
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1answer
518 views

Finding baseline (reference) of nosiy data and lag/lead between 2 signals

I have 2 datasets which vary with time as shown in the figure - Sa – Red , Sb – BLACK . I am doing the analysis in R. The entire dataset and a segment of data from 30 - 31 s are shown below - - As ...
2
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0answers
73 views

Modelling of quantization noise with logarithmic steps

I have to modell the quantization noise of ADC. I only know that the maximum relative error is 1 dB. Since this is logarithmic, I find it hard to formulate an appropriate model for the quantization ...
2
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0answers
137 views

Check if I has right: Is this the Extended Kalman Filter

I have learn the Kalman-Buncy filter for the LQG controllers. I know that this is a signal processing forum and not robotics not math forum. But Extended Kalman Filters are daily discussed here. ...
2
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1answer
378 views

Creating a noise model with a fixed PSNR

My goal is to create a noise model so that the PSNR of the noisy image compared to the original is some pre-defined constant $\alpha$. This means the mean squared-error will also be a constant. My ...
2
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0answers
395 views

Connections between quantum field theory and signal processing

I've been working with quantum field theory on the basis of it being a stochastic signal processing formalism for a number of years. The projection to fourier components within the forward light-cone ...
2
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0answers
747 views

Kalman filter to filter noise from acceleration data

I would like to apply a Kalman filter to remove noise from my measured acceleration data. The idea is then to compare the results obtained in this way whit the results obtained by applying a low-pass ...
2
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0answers
265 views

1/f noise generation

Recently I was reading a paper about the pink noise generation. But I don't have any background of this field. I am confused with some part in the paper. First, the Voss's algorithm generated a ...
2
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0answers
208 views

Purple Noise Modeling / Differentiated White Noise (Kalman Filtering)

I am designing a Kalman Filter for a signal which features a certain kind of noise and I do not know how to model it properly in the filter. The noise is constructed from a white noise source, called $...
2
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2answers
396 views

filter design for ECG

I would like to ask how to design a digital filter to remove $50$ Hz interference on an ECG signal. Do I need to use notch filter? Thanks.
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0answers
227 views

Noise analysis with periodogram. problem with different resolutions

I don't understand what happened in my simulation. I would like to perform a trade off between 2 ways to estimate power in frequency bands. I want to detect spurious frequencies. First method: I ...
2
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0answers
405 views

Extended kalman filter for accelerometer data on shaking table

I am using an accelerometer to record the motion of a shake table (a rocking table) which moves forward and backward in one direction. The signal is very noisy and decided to use Extended Kalman ...
2
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1answer
1k views

Finding circle in binary image (R, not matlab)

How would I extract the circular area of a binary image which looks like: The two rods emerging from the side of the circle are noise. I know of the hough transform in Matlab. However, I am using R ...
2
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0answers
76 views

Smoothing data from a 3D camera

The camera uses two cameras and reflective infrared markers to compute 3D positions. For recognized marker configurations, the camera computes a translation and an orientation (quaternion). For stray ...
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0answers
2k views

Equivalent number of looks (ENL) calculation

As stated in gagnon1997speckle in paragraph 2.2, under the unit-mean noise assumption one can say that: \begin{equation} ENL = \left(\frac{\bar{y}}{\sigma_{y}} \right)^2 = \frac{1}{\sigma_{n}^2} \end{...
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53 views

Noise variance and sampling

I am new to signal processing, so please bear with me. My question applies to any general problem of estimation from noisy measurements but I will like to understand this through a problem given here. ...
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1answer
48 views

Time warping / frequency modulation natural examples?

"Time warping" defined as $$ x(t) \rightarrow x(t - \tau(t)) $$ where $|\tau'(t)| < 1$ ($=1$ is time stopping, $=0$ is time shift, $>1$ is time reversal). Where can this occur? A ...
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1answer
59 views

Impulse response $h[n]$ of a non linear I/O equation

my question concerns an assignment that was given to us at school. We have been given a list of I/O equations and it is required, for each of them, to find the impulse response $h[n]$ and the ratio ...
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0answers
41 views

Remove Noise from Discrete Signal with given Noise Model

I am interested in finding the true signal $p \in \mathbb{R}^D$ of an observed discrete signal $t \in \mathbb{Z}_{+}^D$. I know that each observed $t_{i}$ with $1 \leq i \leq D$ is the result of a ...
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0answers
27 views

Maximum Likelihood for Colored Noise: Implementing using Viterbi Algorithm

I have a question regarding the ML estimation in presence of colored noise, i.e., Additive Colored Gaussian Noise. I want to implement this using a Viterbi algorithm, since I need to take the '...
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1answer
35 views

Differentiate betwee sibilant "sssh" voice sounds and instruments like hi-hat?

How would I differentiate betwee sibilant "sssh" voice sounds in a music track and a similar sounding instrument sounds like hi-hat or cymbals?
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0answers
173 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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0answers
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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0answers
35 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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0answers
28 views

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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0answers
28 views

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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1answer
58 views

Matched filter for recieved RF digital packet by LPF

Im transmitting by cc1350 launchpad microprocessor digital RF Packets, transmitted modulation FSK. bit rate of transmitting is 50Kbouad, frequency of transmitting is 868MHZ . Im sampling the signal(...

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