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Questions tagged [noise]

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

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Remove constant noise from Goertzel output

I'm trying to analyze a signal recorded from an analogue phone line and do DTMF recognition using a Goertzel algorithm. However, due to a fault in the hardware, there is a constant 50Hz power line ...
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Denoising Oscilloscope data the right way [python3]

I need to plot large oscilloscope data sets. They are too large (100 million Values) to plot all of them in a for loop. If I try to do that it results in a ...
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Why do we need to write the noise as randn(2,1)./sqrt(2*SNR) instead of randn(1,1)/sqrt(2)?

I saw this code, about the error probability of on/off signal ,on the internet ...
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Question About Sampling White Noise

Assuming that we have a continuous signal $v(t)$ $$v(t) = \int_0^t g(u)\, \mathrm du\tag1$$ where $g(t)$ is white noise.Then take the derivative of it. $$\frac{\mathrm d}{\,\mathrm dt} v(t) = g(t)\...
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Getting SNR of reconstructed signal in MATLAB

I am trying to run code to compare the efficiency of various basic sampling methods such as ideal sampling, natural sampling and so on. I want to then use average power to see how accurate the ...
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How to achieve a smoothed frequency phase response with no outliers

I have two sampled signals, which I then perform wavelet analysis on, by synthesising the Filterbank, perform the dft on each kernel, and the dft on the sampled signals, and multiply together. ...
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Downsampling by block averaging

Many spectroscopic detectors used to study light absorbance as a function of time. These detectors cab sample data at 160 to 250 Hz. There is an option of choosing lower sampling rates such 80, 40, 20,...
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Intelligent Noise Removal in Data

This question is linked to this question: I have this data: ...
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43 views

PSD subtraction

I am interested seeing the difference between two power spectral densities (PSD) as a noise reduction exercise The blue line is the psd of my signal, and the the orange line is the psd of the ...
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Signal ECG Noise correction

in order to make the correction of an ECG signal full of collector noises from a sensor, I use the fast Fourier transform (FFT) method and it sends me complex numbers, my problem is that I do not know ...
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Signal ECG , collecte & visualize data

I am currently working on a sensor that visualizes an ECG signal and visualizes its data. Its principle is that it has 3 electrodes that must be placed in specific parts of the body .... I would like ...
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22 views

What does "noise power is assumed to be the same at all nodes

I was reading a paper about communications between nodes, and in the simulation section they gave the condition of the simulation as follow : "...The noise power is assumed to be the same at all ...
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processing a very noisy signal

I work on an ECG signal that I collect from a sensor, and it is very noisy. Having researched it above I read that FFT or so Nyquist-Shawon's casting theories were advised, being novice in the field ...
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Should I increase the mean or the variance of Gaussian noise?

I am new in DSP. I am currently working with a project and I want to try which algorithm works better given different image noises. To test it out, I have been using the Gaussian noise in images. ...
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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)...
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Signal acquisition equipment phase noise

I would like to check if there is a way to enhance an RF equipment's phase noise figure. The considered RF acquisition homodyne system includes a mixer for carrier demodulation, amplifier and filter ...
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Chi-squared distribution variable spectral analysis

I an interested in spectral analysis of a random signal. Assume the signal $n(t)\sim\mathcal{N}(0,\sigma^2)$ is followed by the white Gaussian noise with zero mean and $\sigma^2$ variance. The test ...
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FM/CW NOISE RADAR

I am trying to generate the white noise signal which I want to modulate using the sinusoidal wave for the radar-target application. I used fmmod() but I am confused is this right choice. I came across ...
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Classifying and filtering out noise from zero crossings

Note: I know absolutely nothing about zero crossings nor signal processing in general. However, I am doing programming exercises that require them. I've searched around but I cannot understand most of ...
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How to add noise with given autocorrelation to signal in Matlab?

My question is a mix of signal processing and Matlab coding. I have an FIR filter with added noise $w_n$ $$x_n=\sum_{m=0}^{N_h-1}h_mg_{n-m}+w_n.$$ Now the noise $w_n$ has the autocorrelation $$E[...
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Encoder: Quantization in Frequency Domain

The article, "Let’s build an MP3-decoder!" describes quantization noise in the time domain: [masking] This property is very useful: not only can the nearby masked signals be removed; the audible ...
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Are There Common Values of Standard Deviation for Gaussian Noise of an Image?

For example, it occurs to me that there might be a standard deviation value of Gaussian noise in which the human eye could no longer distinguish an object because the standard deviation is very high ...
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Autocorrelation function and product of summations

Let $u[k]$ be a white gaussian noise with variance $\sigma^2$ and $y[k]=\sum\limits_{i=0}^q b_i u[k-i]$, that is a moving average model. I am trying to compute the autocorrelation function of $y[k]$: ...
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audio analog input + usb data cable = sound noises

I connect my android smartphone from audio jack output to my pc audio input and get a good analog sound signal. But when I connect this smartphone to the pc with usb data cable the analog sound ...
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1answer
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AWGN : Recombining AWGN to obtain new AWGN

I am a newbie to AWGN. My professor has given me a task of taking 4 different AWGN (0 mean and SD of 1) channels (Lets say each channel has 100 samples). Then I recombine these noise samples by ...
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Finding periodicity in discrete events

I have a program that detects events in a large amount of measurement data. When it detects an event, it writes a timestamp. I have thousands of event timestamps. What I wish to do is detect if there ...
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When a stochastic process would be a beneficial model in terms of noise

Let's say we have an image/signal with some noise in it. When would it be beneficial to model the signal as an outcome of a stochastic process? More specifically: How significant would noise have to ...
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Noise Reduction: How can I filter out saw or other tool noises?

I recently came across old recording from the 1930's. Unfortunately not only is the quality low, it's a bunch of carpenters talking as they saw things and make all sorts of other noises. I've tried: ...
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Is it possible to just remove the noisy part of signal?

Is there a way to scan through a signal and remove the parts that don't look "normal". This would mean using more advanced then a simple pass band filter, but something that can look at a period in ...
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About the variance of the white noise process

I saw such an example in a book. Assume that the $w(t)$ is a white Gaussian noise with zero-mean and power spectrum density $N_0/2$. Now, consider the sample function: $$n(t)=\sqrt{2\over T}\int_{...
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Cleaning telephone audio

I have telephone audio at 16kHz and I am trying to use it with a speech transcription engine that converts spoken letters to text. However, the engine has some difficulty transcribing certain letters ...
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1answer
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About the variance of the coefficient of narrowband noise when using signal-space representation

Assume that n(t) is a white Gaussian noise process with zero-mean and power spectrum density $N_0/2$. By using the signal-space representation, it can be expressed as: $$n(t) =\sum_{j=1}^N n_j \...
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How to calculate the variance of noise when an image is downsampled?

I have a noisy image for which I know the noise variance. (Basically I created noisy image by adding noise). Now, I'm downsampling this noisy image. How does the noise variance change? Is it possible ...
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Data transmission with SNR<0dB?

I encounter a situation that it is very beneficial to limit the signal strength below noise floor. I know that the Shannon–Hartley theorem suggest that it is possible: I searched over the internet ...
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Methods for subtracting gravity from accelerometer data

This could feel like a repeated question, but please bear with me. In my work we want to compare different methods of subtracting gravity from an accelerometer data to decide on the better way and ...
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2answers
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Audio sounds oddly distorted [closed]

https://clips.twitch.tv/TangentialObliqueLobsterSaltBae https://clips.twitch.tv/CharmingBashfulAlfalfaRickroll https://clips.twitch.tv/NaiveKindGorillaGivePLZ (Disclaimer: These were not recorded on ...
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Eigenvalue based detection threhsold of sub-sampled signal

At the receiver side, I have an observed signal sampled at a rate much lower than the Nyquist rate. I would like to know how many frequency components there are in the signal. I applied the singular ...
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Method for the Localisation of Impulsive Noise in Speech Signal

I'm sorry if this question has already been answered, but I couldn't find anything. I'm working on a program for noise detection and need to locate the position of impulsive noise. The following image ...
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Particular Correlation formula

I'm reading a book where the autocorrelation of white noise is expressed as: What is the term $Q(k)$ and why is is expressed as an average value of a dot product ?
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Proof that first difference filter amplifies noise

I'm a bit befuddled by noise's effect on derivative filters. I've always 'known' that straightforward first difference derivative filters of discrete signals amplifies noise, but I'm struggling to ...
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Why does White Noise in images imply noise in adjacent pixels are independent?

My professor said in the class that for "Additive White noise, the noise in pixels adjacent to each other are independent". How? This is what I have got so far: White noise implies that PSD (Power ...
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1answer
53 views

Active Noise cancellation for non periodic signals

I observed that the coded algorithm for active noise cancellation is not able to cancel some of the signals like a human voice. Is there any solution for this? Can we really cancel non-periodic ...
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Accelerometer signal processing

I'm new signal processing (this is my first pratical application), so I ask sorry if my question is simple. My challenge is to see the displacement of accelerometer when I have vibration too. I do ...
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41 views

Power Spectral Density of discrete White Gaussian Noise defined with variance and sampling interval

From Creighton and Anderson Chapter 7 on Gravitational Wave data analysis: Please explain where the delta t and the limit came from in this derivation.
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Reducing noise on several Transfer Function measurements

INTRODUCTION I want to obtain the transfer function of certain system (a ground "path", in this case) using an impact hammer for the excitation and one accelerometer (measuring vertical direction ...
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1answer
61 views

Does dividing the magnitude spectrum of white noise by sqrt(2) give an RMS magnitude spectrum?

I understand that the RMS Amplitude of a sinusoidal signal is around 0.707 ($\frac1{\sqrt2}$) times the Peak Value, but this is not true for noise. However, an FFT of a noise signal indicates ...
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2answers
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What is Causing a Noise Signal in USB Audio Recording?

I am experiencing the following peculiar noise signal when recording from my Behringer Xenyx Control 2 over USB. There is frequency at around 2293 hz as show: And over time, it produces the ...
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How to find the instantanous SNR over Fading channel

I would like to prove that the instantnous SNR of flat fading channel $$y=hx+n$$ is $$\gamma=\frac{|h|^2}{N_0}P$$ where $E\{z\}$ is the expectation of $z$ and $$ E\{x\}=P $$ $$ E\{n\}=0 $$ $$ E\{...