Questions tagged [noise]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
0
votes
0answers
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
votes
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 ...
0
votes
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
votes
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!
0
votes
0answers
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(...
1
vote
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 $...
1
vote
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 ...
0
votes
0answers
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?
-1
votes
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?
1
vote
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 (...
0
votes
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
votes
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 ...
0
votes
0answers
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 ...
0
votes
0answers
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
votes
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: ...
0
votes
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 ...
1
vote
0answers
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 ...
0
votes
0answers
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 ...
1
vote
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?
2
votes
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 ...
1
vote
0answers
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
votes
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 ...
0
votes
0answers
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}}{...
2
votes
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 ...
2
votes
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 ...
1
vote
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 ...
0
votes
0answers
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 ...
3
votes
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 ...
1
vote
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}+\...
1
vote
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/...
0
votes
0answers
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 ...
1
vote
0answers
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 ...
2
votes
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
votes
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 (...
0
votes
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 ...
1
vote
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 ...
1
vote
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, ...
0
votes
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 ...
0
votes
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 $...
0
votes
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?
1
vote
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 ...
1
vote
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 ...
0
votes
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 ...
0
votes
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?
1
vote
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 ...
0
votes
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?
1
vote
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 ...
0
votes
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)\...
0
votes
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 ...
2
votes
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 ...

1
2 3 4 5