Questions tagged [noise]

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1answer
147 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
71 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
15 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
22 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
20 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
52 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
66 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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0answers
6 views

Does any practical system actually use the Kirchhoff-Law-Johnson-Noise (KLJN) secure key distribution mechanism?

http://www.scholarpedia.org/article/Secure_communications_using_the_KLJN_scheme describes the Kirchhoff-Law-Johnson-Noise (KLJN) secure key distribution scheme, which is based on two switches and an ...
0
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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
75 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 ...
0
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1answer
46 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
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0answers
29 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
47 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
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1answer
33 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
20 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
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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 ...
0
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1answer
62 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
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2answers
117 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
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4answers
128 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 ...
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0answers
37 views

Non-Markovian noise coupled to atomic system

I want to calculate the density matrix element's average over all the realization of Gaussian colored noise when the atomic system is coupled to the said noise. I know how to do it for atomic energy ...
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0answers
13 views

Question on the correlation function of dichotomous Markov noise

Setup: A two-state switching process $I(t)$ between two values $\Delta_1$ and $\Delta_2$ with rates $\alpha$ and $\beta$ can be represented by the transition probabilities $$ P_{ij}(t) = \frac{1}{\...
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1answer
61 views

Calculate dark noise in CCD given a pixel's counts for two exposures

Suppose I took two pictures with the same CCD camera in totally dark room. The first picture was exposed for 1 microsecond, and the pixel given was 20 scales of grey. The second picture was exposed ...
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0answers
18 views

Exponential decay and growth oscillations at beginning and end of Fourier transform of data

I have some data from an photo-detector, which I think should correspond to white noise, but when I plot the Fourier transform of the data, I get a plot with exponential decay at the beginning and ...
2
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1answer
99 views

Identify reasons for laser intensity fluctuation

I got a Mitsubishi LPC-826 laser diode (single mode) with laser driver iC-HG. There is no cooling device, but data was captured after 30 mins switching on (which should be temporally stable). The beam ...
0
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2answers
67 views

Shot-Noise in optical detectors

I'm somehow struggling with the definition of the SNR (S/N) of optical detectors when it comes to shot-noise. I found some literature where it is defined as follows $$SNR = N/\sqrt{\bar{N}} = \sqrt{\...
5
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2answers
108 views

Do planes have to be noisy?

I tend to think of noise as an undesirable waste of energy because the generator was not designed for that purpose. But that doesnt mean this waste can be avoided. So I wonder how much of this noise ...
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0answers
42 views

Is thermal (Johnson) noise intrinsically stochastic?

Thermal (Johnson) noise is caused by electron collitions. Since movement of electrons is intrinsically stochastic according to Quantum Mechanics (assuming the Copenaghen interpretation), does this ...
1
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2answers
93 views

Unexpected wavelength jumps in a laser observed: a fundamental noise source in VCSELs?

I observed an unexpected signal while developing an interferometric sensor using a VCSEL laser. In order to debug this noise I designed the following device that converts minute changes in the laser's ...
2
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1answer
39 views

Unknown pulses from SiPM without any source or detector?

I have a SiPM set up with its PCB, no amplification at all, reading out to an oscilloscope. If I supply 29.8 V, which is the maximum power (with overvoltage), I get some random peaks on the ...
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0answers
22 views

Is there a physical limit to silent quadcopters, and what are the parameters?

Quadcopters can now navigate fairly well indoors. One could imagine many possible uses, including telepresence and security, but which are limited because of the loud noise. Assuming zero 'motor ...
2
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1answer
108 views

Radiation Pressure Noise in Gravitational Wave Detection

I am trying to work out where equation 9 comes from in Martynov et al. (2016), who discuss the radiation pressure noise in the LIGO detector. $$L(f) = \frac{2}{cM\pi^2 f^2} \left(h \nu G_{-} P_{\rm ...
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0answers
41 views

Unit strength Wiener process

I am not much aware of Brownian motion and/or the Wiener process. Recently I have been reading a research paper where they mention a variable $dW$ as a "unit strength Wiener process". My question is ...
0
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1answer
35 views

About sound of non-existent channels on FM

Well, I have learnt about resonant frequency due to series capacitor and inductor, and how the current at resonant frequency is highest, but i am confused about the sound, which appears even when no ...
2
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2answers
112 views

Perfect sound-canceling devices

Noise-canceling headphones can reduce a lot of ambient sound, but they are not 100% perfect. (Especially in the human vocal range.) Is there any physical principle preventing the creation of perfect ...
3
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1answer
57 views

Can one formulate a fluctuation-dissipation theorem in presence of non-Gaussian noise sources?

The fluctuation dissipation theorem relates the linear response of a system to Gaussian fluctuations. The natural question that comes to my mind is the possible derivation of an analogous FDT in ...
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3answers
143 views

Shot noise and single photon detection

I am looking into the noise considerations of a single photon detector, specifically an avalanche detector. I am wondering if it makes sense to think about shot noise when considering a single photon. ...
2
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2answers
762 views

How do silent kettles work? [closed]

I just had to buy a new (electric jug) kettle, and as I was bugged by the loud noise the old one made I was please to see that one can now buy silent ones. At first the new one made just the same ...
3
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0answers
74 views

Transition rate in systems without thermal noise

I've been lately reading about Transition State Theory (TST) and different methods to estimate the transition rates between metastable states in the context of chemical reactions using the review ...
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2answers
70 views

Estimate of the period of noisy “event counting” data

I have a set of experimental data, which come from a periodical event. More specifically, these are detections from a single photon detector, so there is no intensity, I only have the timestamps of ...
1
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2answers
38 views

Noise level x amount of meters away from an outdoor singer: sphere or semi-sphere?

When computing the noise level x amount of meters away from a singer who is singing outdoors, should one rely on the standard formula $I=\frac{P}{4πr^2}$ (and then convert 'I' into decibels) or ...
2
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0answers
36 views

What is all the known information contained in thermal noise?

I've read up a little bit on thermal noise, which is an unavoidable noise in materials when $T>0K$. Thanks to this noise, by measuring the voltage across a material, it is possible to extract the ...
1
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1answer
76 views

Noise covariance matrix

I've been trying to understand this paper. The paper seems to be about analyzing noise properties of a superconducting coplanar waveguide microwave resonator. They use an IQ mixer to perform ...
0
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1answer
49 views

Noise reduction approaches in optical spectral measurement

I am using an optical spectrometer to measure some surfaces in the visible, and since the signal is quite noisy I wondering what would be the best way to reduce the noise. In particular, are there ...
-1
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1answer
5k views

Noise cancellation device for entire rooms [closed]

I recently met a group who were exploring active noise cancellation devices for entire rooms. Their approach essentially revolved around detecting incident noise on the room and blasting inverse ...
1
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0answers
18 views

Why a CRT TV shows B/W noise when not tuned [closed]

When an old color tube TV with no relevant digital bits in it is not tuned to any TV station, the noise is black & white. Why is the noise not all RGB?
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0answers
32 views

What is a zero dimensional stochastic system?

I happened to read a statement about Zero-dimensional stochastic systems in the context of Noise-induced phase Transitions (https://doi.org/10.1140/epjb/e2018-80624-9). I am not sure what does a zero-...
2
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1answer
97 views

Why are the active noise cancellation headphones subjectively better in reducing “periodic” noise?

According to experience of mine and of my friends using active noise cancellation headphones, the technology is much more efficient in reducing "periodic" noise, such as humming of jet engine, fridge ...
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0answers
27 views

Balancing noise energy contributions with friction term

I'm looking for a result that would say something about the way in which to pick a proper constant $\sigma$ in generic models of the form: $$ \ddot{x} = - \gamma \dot{x} - \nabla V(x) + \sigma \xi(t) $...
1
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1answer
95 views

Sudden change in noise levels [closed]

This is real life issue I am having currently and I am puzzled as to why it happened. I posted the question in the engineering section but it was put on hold as too broad. I have no other way to ...
1
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3answers
166 views

Converting from free field to reverberant field (Noise break out to outside)

If you have a noisy room (reverberant field) and you want to know how loud it sounds to a guy standing in the park outside how do you calculate that. I have a formula in a book about noise break-out ...