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Questions tagged [noise]

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2 votes
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Does a rubber mat reduce the impact to the floor below?

My lack of physics knowledge is preventing me from solving an everyday life problem. Please bear with me! Say I have a second-floor apartment and I want to do deadlifts. I am afraid of the floor ...
fumoboy007's user avatar
0 votes
1 answer
38 views

Are all types of noise a result of lack of complete knowledge about the given system? What does this say about the physicality about information?

I am currently studying the basics of quantum information theory. When we study a system (classical or quantum), any undesirable influence out of our control is usually referred to as noise, and this ...
Pratham Hullamballi's user avatar
2 votes
0 answers
66 views

Fokker-Planck equation for colored noise Langevin equation

I was wondering if there is a way to derive the Fokker-Planck equation for Langevin equation with a general colored noise: $$m \ddot{x} = -\frac{\partial V(x)}{\partial x} - \gamma \dot{x} + F(t)$$ ...
aQuarkyName's user avatar
1 vote
1 answer
48 views

Why and how white noise cancels other background noises?

This idea of white noise cancelling other background noises is quite popular these days and I always wonder how it works? https://www.youtube.com/watch?v=nMfPqeZjc2c This is a sample of white noise. ...
Devansh Mittal's user avatar
0 votes
0 answers
18 views

Does a noise protection wall cancel out sound on the opposite side of the acoustic source?

My town wants to build a noise protection wall on one side along railway tracks. Houses are on both sides of the railway tracks. Obviously the noise protection wall will cancel out sound on the ...
Tesla coil's user avatar
0 votes
0 answers
29 views

What duration of a white noise burst is required for it to be "white" at a given frequency or frequency range?

I am running white noise bursts (with very short ramps on/off to prevent discontinuities) through underdamped resonant bandpasses which are tuned to any given $f_0$ and an underdamped $Q$. Continuous ...
mike's user avatar
  • 321
1 vote
1 answer
37 views

How to standardize the energy of a Dirac delta function relative to sample rate (width) and amplitude?

Background I was instructed that a Dirac delta function (impulse from $0$ to $A$ then back to $0$ at short duration) has a white noise audio frequency type excitation distribution here ie. It should ...
mike's user avatar
  • 321
1 vote
2 answers
46 views

Is it possible to, like white noise, excite all audio frequencies equally, but with a more immediate & less random burst? Like a signal discontinuity?

I am trying to generate an audio signal that, like white noise, has "equal intensity at different frequencies, giving it a constant power spectral density", but unlike white noise, can be ...
mike's user avatar
  • 321
0 votes
0 answers
19 views

Does it make sense to whiten the data in order to apply a matched filtering algorithm if my dataset consist of a sinusoid + random Gaussian noise?

With a Python program I generated a sinusoid signal and I added to it Gaussian noise. Now I want to compute the optimal SNR by applying a matched filtering algorithm. Since the noise is white (at ...
AleNekro97's user avatar
1 vote
0 answers
32 views

Should the Power Spectral Density be complex?

I need help! I'm trying to calculate the Power Spectral Density of a quantum operator ($\delta \hat{n}(t)$) given by: $$ \delta \hat{n}(t) = A(t)\delta\hat{a}(t)+A^{*}(t)\delta\hat{a}^{\dagger}(t) $$ ...
Pedro Pinho's user avatar
0 votes
0 answers
21 views

Langevin dynamics with position dependent random force

Suppose I want to solve for some Langevin dynamics. Let us consider a single particle: $$m\ddot {\mathbf r}=-\eta\dot{\mathbf r}+\mathbf F$$ where $\mathbf r$ is position, $\eta$ is viscosity force ...
Mauricio's user avatar
  • 5,476
0 votes
0 answers
50 views

Shot noise coupled quantum system

I have a question about noise in a coupled quantum system. Suppose you have two parallel 1D waveguides, which are separated from each other by a thin tunneling barrier. The subband energies of the ...
B4ckflip's user avatar
0 votes
1 answer
85 views

Mathematical description of random noise

I am trying to mathematically model the noise affecting a certain physical quantity, say $X(t)$. Then, the noisy quantity would be $X'(t)$ which differs by some small value $\delta$ from the ideal ...
Len's user avatar
  • 177
3 votes
1 answer
39 views

Allan deviation power expansion

In the 'Hand Book of Frequency Analysis' S3.2, by W.J Riley the frequency stability of an oscillator is expressed as a combination of power-law noises of the form $S(f)\propto f^\alpha$, where $f$ is ...
jamie1989's user avatar
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12 votes
3 answers
4k views

Avoiding radar detection using active noise control instead of a stealth fuselage

was reading about different stealth technologies used by modern aircrafts to avoid radar detection. Wouldn't it be easier to have a receiver on the airplane listening on the radar frequencies and then ...
Henry Skoglund's user avatar
0 votes
1 answer
95 views

Is this a valid alternative definition of the delta function?

The delta function can be defined as: $$ \delta(x) = \int_{-\infty}^{\infty} e^{-2\pi i k x} \, dk $$ Loosely speaking, I can understand this because unless $x=0$, the complex exponential oscillates ...
user38274's user avatar
  • 426
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0 answers
44 views

Poisson noise on $a_{\ell m}$ complex number: real or complex?

In a cosmology context, when I add a centered Poisson noise on $a_{\ell m}$ and I take the definition of a $C_{\ell}$ this way : $C_{\ell}=\dfrac{1}{2\ell+1} \sum_{m=-\ell}^{+\ell} \left(a_{\ell m}+\...
guizmo133's user avatar
0 votes
0 answers
59 views

Measurement paradox

When building electronics to measure usually it is asked what the bandwidth of the signal is and what is the frequency range usually done to limit noise bandwidth and thus have more SNR. To me it ...
Weijie Chen's user avatar
0 votes
1 answer
34 views

How do I compute the bounds of random walk for a given ellapsed time?

I am trying to model random walk of a gyro, given some manufacturer specifications of maximum random walk in units of degrees per root-hour. My first step was to generate white noise with a standard ...
rocksNwaves's user avatar
1 vote
0 answers
53 views

Novikov's theorem for time-independent functional

$\textbf{Introduction}$ Given a Gaussian-colored noise \begin{equation} \begin{split} &\langle z(t)\rangle=0,\\ &\langle z(t)z(t')\rangle=C(t-t').\\ \end{split} \end{equation} A given ...
J.Agusti's user avatar
-3 votes
2 answers
120 views

Why doesn't the sunlight make noises on home satellite dishes?

One of my friends asked me a question to which I could not find a clear answer. We know that the sunlight spectrum includes the entire wave frequencies including those (of the order of 1 GHz) that our ...
Mohammad Javanshiry's user avatar
0 votes
1 answer
127 views

Energy spectral density vs power spectral density vs power spectral density per unit time

I recently started research to measure the voltage noise spectrum of materials to study their phase transitions. Before understanding physics, I am now confused by the three terms used in literature: ...
Yuxin Wang's user avatar
0 votes
1 answer
56 views

Noise spectral density for GW detector

I am reading the book Gravitational waves by Maggiore. On page 337 in Eq. (7.6) he defines the noise spectral density as $$<\tilde{n}^*(f)\tilde{n}(f')>=\delta(f-f')\frac{1}{2}S_n(f)$$. I want ...
jojo123456's user avatar
1 vote
1 answer
78 views

Modelling phase noise for self-hetrodyne method

I am trying to model the phase noise $\phi(t)$ of laser used in self-hetrodyne method using python code. The noise is time-dependent. The noise follows the condition that $$<(\phi(t)-\phi(t-\tau))^...
FearlessVirgo's user avatar
1 vote
1 answer
90 views

Fermi calculation to show that all crowds sound the same?

I live in an arabic speaking country, and while I was sitting in a food court today, I noticed that the sound of the crowd was the same as the one I see in the stereotypical sound of the crowd. I have ...
Babu's user avatar
  • 7,960
3 votes
1 answer
234 views

How do physicist keep entangled particles entangled while moving them/storing them?

Once an entangled particle is measured, it's wave function collapses. From my understanding, any sort of information exchanged to the particles can be considered a mistaken measurement. So how do ...
Sophia's user avatar
  • 71
1 vote
3 answers
107 views

Why does an increase in my sound intensity lead to an increase in frequency range?

I am a biologist studying frogs, and as part of my research I use hundreds of thousands of audio recordings (.wav) from autonomous recording units. I use various software to create recognizers that ...
Anna's user avatar
  • 11
0 votes
0 answers
32 views

Ifluence of street illumination on laser radiation

Many people have said that the noise that affects laser light is proportional to the square root of the illumination. But I can't find the formula. Can anyone help? Maybe it has something to do with ...
A PH's user avatar
  • 1
3 votes
0 answers
88 views

Ito-Stratonovich drift term for spatial white noise

Suppose I have a Langevin equation with multiplicative noise of the form $$ \dot{x} = f(x) + g(x)\eta(t) $$ where $ \eta(t) $ is a Gaussian white noise with zero average, unit strength, and delta ...
llangford1's user avatar
1 vote
1 answer
466 views

From Lindblad operators to Kraus operators: an explicit example of a dephasing noise model

I'm trying to understand how to obtain a set of Kraus operators from Lindblad master equations. For a $1$-qubit dephasing noise model, it is well-known that the set of Kraus operators is $\{ \sqrt{p}I,...
Jon Megan's user avatar
  • 177
0 votes
0 answers
72 views

What's the formula of SNR (Signal to Noise Ratio) to dipole antenna array (eg, LOFAR) look like?

It was wellknown that the SNR of single dish telescope reads $$s/n=\frac{P_s}{P_n}=\frac{P_{s}}{T_n}\sqrt{\frac{t}{B}},$$ where $P_s$ is the collected power, $T_n$ the noise temperature, $t$ the ...
Hunter's user avatar
  • 1
3 votes
2 answers
72 views

In what respect does the wave pattern of a noise and music differ?

Does the wave pattern of musical sounds contain only harmonics (other than the fundamental frequency) while noise contains random overtones (that are not harmonics)?
Golden_Hawk's user avatar
  • 1,038
3 votes
1 answer
184 views

Dephasing noise as a decoherence model - Effect on a generalized GHZ state

Some input: Consider a decoherence process modelled by $$\mathcal{E}\left(\rho\right)=p_0\rho+(1-p_0)\sigma_z\rho\sigma_z$$ with $p_0=(1+e^{-\gamma t})/2$. One can readily find that this leads to $\...
manuel459's user avatar
  • 438
1 vote
0 answers
24 views

Minimum Observable Offset Frequency in Leeson's Formula

It has been argued in some publications that the age of the universe represents a lower limit on observable frequencies (in their paper, corresponding to a value of $10^{-17}$ Hz). The authors do not ...
CuriousDroid's user avatar
1 vote
0 answers
35 views

Why does metal wire make noise but not string [closed]

why when I vibrate metal string it make noise but when I vibrate string it no make noise?
Fakhryou's user avatar
1 vote
0 answers
49 views

Applying a simple noise model to the ghz state

I want to calculate the effect of a specific noise model on the GHZ state but fail to do so. I think I am missing some basic rules established for working with operations on density matrices. More on ...
manuel459's user avatar
  • 438
1 vote
0 answers
280 views

Derivation of Heisenberg-Langevin equations for an atom coupled to a reservoir of harmonic oscillators

I have been working on the paper of A. Lezama on the "Numerical investigation of the quantum fluctuations..." (2008) and been trying to replicate their derivation and simulation. However, I ...
Tzekh's user avatar
  • 31
5 votes
1 answer
216 views

What's the smallest signal to noise ratio for which a signal has been extracted?

Suppose we have some physical variable $y$ that is changing in some way and we want to detect this change in the presence of noise (e.g. white noise) in that same physical quantity. For example $y$ is ...
Andrew Steane's user avatar
1 vote
1 answer
60 views

Magnetic field modeling with noises

I am trying to make a 3d grid of a magnetic field with some noises (which will be added to the ordinary field) for a computer simulation. I have the formula for the ordinary field, also I am using a ...
Norayr Galikyan's user avatar
3 votes
1 answer
21 views

Experiment preparation - Box to reduce background photons noise

I am planning to perform experiment with a photomultiplier tube (PMT) in my lab. The system is not large, with a length scale of about 10 cm. I am looking to reduce the background photons noise as ...
Sagigever's user avatar
  • 545
6 votes
0 answers
74 views

Does 5G affect your physics experiment?

Our institution wants to lease a nearby roof for a 5G mast. Has anyone experienced the installation and operation of telecoms infrastructure - particularly 5G - significantly affecting physics ...
NLambert's user avatar
  • 537
1 vote
1 answer
116 views

Derivation of sound wave propagation equation

I am trying to derive the sound propagation equation like this. $$\frac{\partial^2 P'}{\partial t^2} = c^2\left(\frac{\partial^2 P'}{\partial x^2}+\frac{\partial^2 P'}{\partial y^2}+\frac{\partial^2 P'...
Kinnikuman's user avatar
2 votes
0 answers
51 views

How do different $|\text{Alive}\rangle+|\text{Dead}\rangle$ kind of states behave under decoherence?

I am looking for literature that investigates said behaviour for spins. So far I found many papers on how to measure the macroscopicity of states and therefore a classification of macroscopic states. ...
manuel459's user avatar
  • 438
1 vote
0 answers
36 views

Can we collapse noises by reducing temperature? [closed]

Is it possible to reduce noises to any extent by decreasing temperature? please give answer using reference to article or website.
mohammad rezza's user avatar
1 vote
1 answer
40 views

Why wireless radios start making buzzing noise when I switch on some electrical appliances?

This question has possibly been asked a numerous number of times already, by many people in many places, but nowhere can I find a precise answer to my precise question. When I turn on, say a ceiling ...
QuestionTheAnswer's user avatar
0 votes
0 answers
23 views

How to add Gaussian noise to light wave

I want to find a method that can add independent Gaussian noise to different incoming light waves; Or find a noise light source that can emit light with Gaussian noise.It would be great if there were ...
Jack_Von's user avatar
1 vote
1 answer
35 views

What is the fractional frequency stability of a thermal damped harmonic oscillator?

Suppose I have a lightly driven (classical) damped harmonic oscillator at temperature $T$. Suppose $\omega$ and $Q$ are specified as well as the mean energy $\bar{E}$ in the oscillator due to the ...
Jagerber48's user avatar
  • 13.9k
3 votes
2 answers
138 views

What limits mechanical watch precision? [closed]

It seems like good mechanical watches gain or lose +/- a few seconds per day. 5 s/day corresponds to a fractional frequency stability of $5\times 10^{-5}$. What limits this stability? Obvious ...
Jagerber48's user avatar
  • 13.9k
0 votes
1 answer
95 views

Is gravity of matter similar to temperature?

Apart of general relativity and the quantum theory postulate o gravitons I am looking for an alternative quantum physical interpretation of gravity of matter? Watching this short video-cut from Dyson'...
Markoul11's user avatar
  • 4,099
0 votes
1 answer
52 views

Why does a non-gaussian distribution imply noise in LIGO?

So I'm trying to understand why do we expect a non-gaussian distribution to imply correlation in LIGO? Like how do we know the default noise distribution is gaussian? I am concerned about coordinate ...
More Anonymous's user avatar

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