# Questions tagged [noise]

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### How can I determine an error on total noise?

I am analyzing the data for an experiment, where we measured the total noise in a system. The total noise is defined as the variance of the signal (and is equal tot the integral over the noise ...
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### Feynman claimed "The ear is not very sensitive to the relative phases of the harmonics." Is that true?

In The Feynman Lectures on Physics, Dr. Richard Feynman claimed that the ear (I assume he meant the human ear) is not sensitive to the relative phases of harmonics. However, I was asked to test ...
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### Can absolute silence exist and how are thermal and quantum noise a limit? [closed]

For my exam, I must answer the question: can absolute silence exist? While doing research, I obviously heard about noises internal to our body and noises external to our environment but I also heard ...
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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 ...
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### 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 ...
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### 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: $$m \ddot{x} = -\frac{\partial V(x)}{\partial x} - \gamma \dot{x} + F(t)$$ ...
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### 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. ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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: $$\delta \hat{n}(t) = A(t)\delta\hat{a}(t)+A^{*}(t)\delta\hat{a}^{\dagger}(t)$$ ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
108 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 ...
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### 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 ...
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### 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?
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### 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 ...
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### 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 ...
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### 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 ...
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