# Questions tagged [noise]

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13 views

### How to experimentally verify, if the intensity of light from an External Cavity Diode Laser (ECDL) is shot noise limited?

I have an ECDL and i want to experimentally verify if it is shot noise limited or not. Any reference will be helpful.
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### When will active noise canceling headphones create perfect silence? [closed]

Active noise cancellation works by creating the mirror image of a sound wave to cancel it. The digital signal processor (dsp) inside the headset analyzes the noise and inverts the signal. When will ...
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### Difficulty bounds in a white noise model

Suppose we make a measurement in a real/virtual experiment for which the noise is given by a white noise (Gaussian) model. Suppose also that we have a very good filter or machine learning (ML) model ...
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### Why does shot noise rise with frequency in LIGO sensitivity?

In plots of the sensitivity of the LIGO interferometer, photon shot noise is the dominant noise source at the high frequency end, e.g. this graphic: It appears to rise roughly in linear proportion ...
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### Commutator of an operator with its Hermitian adjoint in linear quantum systems

I have a commutator of a single-mode photon field operator $\alpha$ with its Hermitian adjoint $\alpha^{\dagger}$. [$\alpha$, $\alpha^{\dagger}$] When this commutator gives a negative value, $\alpha$ ...
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### Under what assumptions does $\langle\eta(t_1)\eta(t_2)\rangle=\int d\eta_1d\eta_2\eta_1\eta_2p(\eta_2,t_2;\eta_1,t_1)$ become $\delta(t_1-t_2)$?

In the Langevin model, if we make the assumption that the random force $\eta(t)$ acting on the Brownian particle is a stationary, Markovian, and gaussian process, does it automatically ensure that the ...
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### Compute the variance of spectroscopic Shot Noise in cosmology context

I would like to know the right expression for the expression of variance of Shot noise in spectroscopic probe. Sometimes, I saw $$\sigma_{SN,sp}^{2} = 1/n_{sp}$$ with $n_{sp}$ the average density of ...
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### Pink noise and averaging

Disclaimer: I am aware this is somehow at the boundary between physics and statistics, but I have the impression that it is more likely that somebody doing/studying physics, rather than statistics, ...
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### Is this intuitive understanding of “averaging over all realizations of a noise” correct?

Consider a continuous random variable $\eta(t)$ such that $$\langle \eta(t)\rangle=0, \forall t$$ where the average $\langle ...\rangle$ is taken over all possible realizations of the noise at any ...
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### Why do I hear static when I plug in my earphones incorrectly?

I use simple earphones which are wired with my laptop. Most of the times I unconsciously plug them in without looking and at times instead of going in the port they touch the laptop body near the port ...
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### Deterministic and stochastic chaos

I have a question about chaos, but first a foreword of what I understood. Noise refers to the random variation of values. Usually unwanted, noise causes a measurement to fluctuate over time. Chaos ...
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### Relationship between intensity and sound level

So I know that for every tenfold increase in intensity, the sound level increases by 10 dB. So if the intensity is increased by a factor of 100000, the sound level increases by 50 dB. I also know that ...
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### Noise Cancellation - Destructive Interference

We know that active noise cancelling headphones work by playing a signal in your ear which is 180º out of phase with the ambient noise. If we compare the two waves, the peak in one wave is completely ...
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### Relationship between noise spectral density and quantum absorption/emission: I don't understand the derivation

In this paper, on page 57 he performs a calculation that I don't understand. Maybe there is an implicit physical assumption behind so this is why I am asking it here. The context (not necessary to ...
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### Expression for covariance matrix as a function of distance

I am studying a tracking problem in which the measurement noise, assumed to be Gaussian, increases as a function of the distance to the target. I am seeking an expression for the covariance of this ...
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### Can unjammable radio communication be achieved by transmitting an error-correcting code of high-energy pulses in a secret, unpredictable pattern?

Signal jamming seems like an annoyingly simple way to sabotage a lot of interesting ideas. It has historically been used to block reception of propaganda broadcasts, and also to ruin military ...
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### Data augmentation in $k$-Space

I am working on denoising data in $k$-space for MRI (magnetic reasonance imaging) using Convolutional neural networks, and I am wondering what would be some suitable data augmentation techniques ...
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### Normalization of Phase Noise / RF Power Spectrum to 1 Hz RBW

I used a Rohde & Schwarz Phase Noise Analyzer to take some phase noise and RF spectrum measurements. All in all, I'm trying to compute the linewidth of a laser from a measurement. I cannot detail ...
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### How does the Brownian motion of air molecules compare to the threshold of human hearing as a function of frequency?

This fantastic question essentially asks what is the noise floor of air? Both the answer given on that thread and the value stated by Microsoft are around -23 or -24 dBSPL. However, overall loudness ...
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### Force from Johnson Noise

A capacitor in parallel with a resistor will have a random noise $\mathrm{voltage^2}$ across it of average value $V^2 = k_{B}T/C$. If this is a parallel plate capacitor, you can show that the average ...
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### Meaning of $\frac{1}{\sqrt{dt}}$ in stochastic forcing

I am running a 2D fluids simulation with a stochastic forcing $f$ in a doubly-periodic box, i.e. solving $$\frac{\partial \nabla^2 \psi}{\partial t} = J(\psi,\nabla^2 \psi) +f,$$ where $J$ is a ...
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### What is a real model of thermal electrical noise?

A common model for electrical noise is to assume a flat frequency distribution, i.e. white noise. However, this results in theoretically infinite energy. So my question is: What has to be accounted ...
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### Johnson Nyquist noise with voltage driving

In his 1928 paper, Nyquist derives the famous Johnson-Nyquist noise relation which is, to be very precise according to his paper: It gives the variance of the voltage at the boundary of a resistor ...
I have a discrete [non-linear] dynamical system $x_{n+1} = f(x_{n})$. There is measurement error, so my observables are a time series $\left\{ \hat{x}_{n}\right\} _{n=1}^{N}$ where \$\hat{x}_{n}=x_{n}+\...