Questions tagged [noise]
The noise tag has no usage guidance.
204
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12 views
Dicke switching for radars
A question about Dicke switching for e.g. radio antennas.
Some background so that we're all on the same page: fluctuations in the gain of the detector can dominate the low power signal. Dicke ...
2
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0answers
12 views
Derivation for resistor noise using transmission lines
Typically, in the derivation used for resistor noise, I see a hypothetical voltage source (the equivalent noise source) with a source resistance of R, connected to a transmission line of ...
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1answer
74 views
Solving linear Lindblad equations in the Heisenberg picture?
I'm interested in solving the explicit time dependence of operators in a simple open system described by a Lindblad equation. The concrete example I'm interested in is a harmonic oscillator with the ...
2
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1answer
28 views
Frequency analysis
What's the difference between Constant Bandwidth Filter and Constant percentage bandwidth filter?
I mean not just the basic difference but a little detailed one, couldn't find much on the internet!
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33 views
Probabilty Density for $x$
Suppose that I have the function $$x(t)=e^{-b(W(t))^2} \ \ \ \ \ \ \ \ (1)$$ where $W(t)$ is just a Wiener process (i.e. a Gaussian in general). I want to know what the probability density for $x$, $P(...
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1answer
33 views
Nyquist noise and thermal equilibration
Let there be given two identical lumped element resistors $R_1=R_2$ whose heat capacities are also equal and given $C_1=C_2$. We assume the resistors are attached to thermostats, one at temperature $...
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1answer
114 views
Spectral density of fluctuations (white noise/delta-correlated process)
Let I be the current flowing across some junction as a result of N charge carriers of charge q. And let $\langle I (t) \rangle$ be its average.
Assume a particle number distribution such that its ...
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29 views
Octave analysis Versus FFT analysis?
Why is the one-octave method more significant or of great value compared to FFT analysis? Is it because of the sensitivity of the human ears to perceive sound in octaves? is there any other reason?
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1answer
26 views
What frequency ranges are best for speakers? [closed]
I have two speakers, one is a 6-inch speaker and another one is Peavy PR 10 (Large speaker). What frequency ranges are best suited for each of the speakers and why?
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2answers
48 views
How to show connection between measured data (sound in $\rm dB$) and the size of speakers? [closed]
How can we relate the measured data of speakers with its SIZE (speaker)? I have the data on white noise and pink noise (FFT and 1/3 octave), I'm a bit confused about how to show the relationship (...
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1answer
31 views
When is white noise appropriate in physical systems?
Almost every textbook and a journal article that deals with thermal noise in the context of optical fields (such as signal processing, micro-ring resonators, laser sources, etc.) assumes that the ...
2
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1answer
58 views
Modelling sky noise using a 2D array with plane waves
I have a question about modeling sky noise which should be filtered by a spatial filter 4f system. My approach for this task is to use a 2D array with random amplitude values and another 2D array that ...
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12 views
Large signal for short time vs. small signal over longer time
I am trying to understand if using a lock-in amplifier for noise reduction will help at all in the following scenario:
I have a signal that I generate which is being detected by some detector that has ...
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28 views
Intuition behind Johnson-Nyquist noise?
I've been doing a lot of reading on Johnson-Nyquist (thermal) noise lately, and sadly much of the material I've come across either looks at things from a very engineering prospective (that is, little ...
2
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2answers
39 views
Is it possible that a tall bush could actually severely block nearby sounds/noises?
I live (against my will) on the bottom floor of an apartment building, with a car road nearby. I made this text illustration to help you see the situation:
...
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1answer
37 views
How can I tell if a photodetector is thermal noise limited or shot noise limited?
Most datasheets for photodetectors only specify the noise equivalent power, making no distinction between thermal noise (Johnson noise) and shot noise. For modelling purposes, how do I know whether ...
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22 views
LISA acceleration noise formula
In the Laser Interferometer Space Antenna (LISA) mission proposal document, section 4.2 (page 17) there is a formula for the test mass acceleration noise level:
\begin{equation}
S_a^{1/2}\leq 3\cdot ...
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16 views
Do lightwaves that have been superimposed on by other waves accumulate noise?
My understanding of why light seems to "slow down" when travelling through different mediums is that the photon interacts with the electrons within a given material and this excites the ...
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1answer
46 views
How does one sound drown out another?
If I'm laying in bed at night with the fan on, I cannot hear nearby traffic. If the fan is off, I can hear the traffic. What is/are the principle(s) involved in this phenomenon?
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1answer
39 views
Is it possible to use destructive interference to eliminate sound coming from a road? [closed]
I've been thinking about the problem of how to block or mitigate road noise. Rather than using a physical structure, is it possible to generate directional sound (by any means) that could/would ...
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47 views
Noise power spectral density and $|X(\omega)|^2$. Why are those quantities associated usually ? Their definitions are different
I consider a generic signal $X(t)$. We could imagine to fix ideas $X(t)=\sqrt{R}I(t)$ ($R$ being a resistor and $I$ current flowing through it)
The energy of this signal is defined as $E=\int_{-\infty}...
3
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1answer
86 views
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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28 views
Difference in mathematical formula between signal to noise ratio (SNR) and signal to noise and distortion ratio (SINAD)
I am trying to get a grip on mathematical meaning of signal to noise ratio (SNR) and signal to noise and distortion ratio (SINAD). What I found out is that in terms of power:
$$SNR=\frac{P_{signal}}{...
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1answer
70 views
Force from Johnson Noise
A capacitor in parallel with a resistor will have a random noise $\mathrm{voltage^2}$ across it of average value $V^2 = k_{B}T/C$. If this is a parallel plate capacitor, you can show that the average ...
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1answer
80 views
Meaning of $\frac{1}{\sqrt{dt}}$ in stochastic forcing
I am running a 2D fluids simulation with a stochastic forcing $f$ in a doubly-periodic box, i.e. solving
$$ \frac{\partial \nabla^2 \psi}{\partial t} = J(\psi,\nabla^2 \psi) +f,$$
where $J$ is a ...
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1answer
34 views
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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20 views
Contradicting power spectral densities and autocorrelation in shot noise
I have a white noise generator circuit which involves a Zener diode meant to undergo breakdown across a resistor $R1$, and am trying to compare power spectral densities and autocorrelation of the ...
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0answers
57 views
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 ...
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2answers
32 views
How to express the “size” of measurement noise in a dynamical system
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}+\...
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1answer
144 views
Clean and simple derivation of Johnson Nyquist noise
I am not sure to get the derivation of Johnson Nyquist noise. I would like to understand it under black-body radiation approach.
Consider this reference: http://www.pas.rochester.edu/~dmw/ast203/...
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33 views
What part of static noise in FM radio and analog TV is due to CMB?
When you switch analog FM radio or analog TV channel to non-existing station (in-between channels),- then you hear/watch just plain static noise. Question what I am interested is- what part exactly of ...
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18 views
Is there a graphical summary of which modulation technique to use in communication systems using Visible Light Communication techniques?
I am currently looking at various papers written (some listed at the bottom) that discuss how laser pulses can be modulated to send encoded messages to a receiver for communication systems. The more I ...
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1answer
1k views
Noise cancelling speakers to cancel sound in the room [duplicate]
A thought of mine from class, where not everyone is the "silent kid" type. The teacher would very often need to shout to keep the class barely quiet enough for the students who actually are paying ...
2
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2answers
129 views
Destructive Interference applied to ElectroMagnetic Waves?
For active noise cancelling (in for example headphones) a process called 'destructive interference' is used.
Since Electromagnetic radiation can be described as a wave, could the same process (...
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0answers
24 views
How to determine at what point regeneration of a signal is necessary?
I have a "homework" question that has raised some doubts in my mind about when regeneration of a signal is necessary and whether it can be determined from a given SNR (signal to noise ratio) alone or ...
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0answers
23 views
How to measure Johnson Noise precisely experimentally? [closed]
I want measure Johnson Noise across a resistor having certain over the certain range of frequency or bandwidth practically. I am starting from scratch, how can I build circuitry and instrumentation so ...
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0answers
21 views
What would motivate choosing between an avalanche or Zener diode? [closed]
If I wanted to produce an analog number generator using reverse-biase diode breakdown, what kind of things should I consider when choosing whether to use an avalanche or Zener diode?
For instance, ...
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1answer
72 views
Can a wind turbine be audible at 3.5 kilometres?
Here is the link to the research supposedly claiming that wind turbines can be heard 3.5 kilometres away inside a house 16% to 22% of the time. The article further claims on occasions audible noise ...
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1answer
72 views
Simulate Background Gamma Radiation for Localization [closed]
I'm working on a gamma radiation source localization project. The gamma radiation measurement model is:
$\lambda_k = \frac{I}{(x_s - x_k)^2 + (y_s - x_y)^2} +\lambda_b$.
Where $\lambda_k$ is the $...
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1answer
49 views
Noise generated by ball impacting a rigid obstacle [closed]
How can I estimate the noise of an elastic non-deformable ball that hits an elastic plate that is simply supported?
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3answers
78 views
Noise perception by humans - one vs two of the same noisy appliance - will the noise be “double”?
If I have a clothes washer in a room versus two of the same machine making the same noise, will the noise level be perceived by humans as twice the level it was before?
I'm pretty sure sound is in a ...
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1answer
53 views
Validity of Johnson noise model in current through vacuum
The Wikipedia page says Johnson noise is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium.
I ...
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0answers
56 views
Johnson-Nyquist Noise and the Assumption of a Noiseless Load
I'm a little stuck on a subtlety of RF/microwave design that I find a bit baffling. It has to do with the convention of using of noiseless resistors as loads in circuit noise analysis. I have not yet ...
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2answers
48 views
Johnson Noise experimental measurement
How can we experimentally find out value (extent) of Johnson Noise of any resistor with certain bandwidth and teperature?
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1answer
41 views
Why doesn't stochastic resonance allow us to ignore noise?
I don't know how to formulate the question better. This question is inspired from here where the author states that satellite communication is sometimes lost when radio noise from the sun makes the ...
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0answers
22 views
Is it possible to block sound? [duplicate]
Is it possible to block/eliminate particular noise sounds with artificially generated sound waves or any other ways?
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1answer
25 views
the mechanism of sound generation of plunging jet
can anybody give me an explanation about what is the acoustic source for a plunging jet, like tap flow enter into a basin? is there any exiting theory like Lighthill theory in aero-acoustic to explain ...
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1answer
104 views
Detection of an optical noise with a photodetector, noise-equivalent power (NEP)
I am trying to find the minimum power that can be detected by a photodetector for which I know its noise-equivalent power (NEP).
The standard formulas are:
$$\mathrm{SNR} = \frac{\langle i_s^2(t)\...
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2answers
141 views
Do noise-cancelling headphones make a lot of unheard noise?
The way noise cancelling headphones work is by listening to sound, and created the inverted sound to 'cancel it out'. Doesn't this mean that the headphones create double the amount of noise, but our ...
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4answers
138 views
Why is “a very silent room” louder than “leaf noise” / “breathing noise”?
I recently was at night in my bed room and used the Schallmessung Android App (on a Samsung S7). It showed 20 dB while laying on some furniture. I could not hear anything; to me, the room was ...
