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3
votes
0answers
117 views

Sound - for purposes of vibration

What is the best way to distribute noise from more than one source (I'm envisioning a system with many), within a dome, with the ground as its primary target, at optimal frequencies and volumes to ...
1
vote
1answer
31 views

Vibrational noise for scientific apparatus on a satellite

Say we're running an experiment on a satellite in some earth orbit. For example, maybe we're imaging something with transmission electron microscope or we're catching atoms in ion traps --- really ...
3
votes
2answers
7k views

Why does noise affect FM radio less than AM?

Frequency modulated waves are less susceptible to noise compared to amplitude modulated signal. This is because the information in an FM signal is transmitted through varying the frequency, and not ...
0
votes
2answers
169 views

Noise cancellation solution for pool filter motor [closed]

I live in a condo, there is pool filtering equipment located outside my bedroom. Can anyone suggest a noise cancellation solution for the hummmm of the motor?. The equipment is in a 12ft x 12ft x 3ft ...
2
votes
0answers
173 views

The origin of contact noise?

I was trying to measure the noise of a device with metal probes. I was not sure whether I should trust the results because I was told contact noise might contribute to some degree. I am a little ...
0
votes
1answer
200 views

Making pink noise (1/f) using list of frequencies [closed]

I would like to see what type of noise I would get if I used just the frequencies in my voice. I created a matlab array using fft to get a ...
7
votes
1answer
8k views

What part of the fan blade actually does the noise generation?

I'm trying to identify the sources of noise in spinning fan blades and what causes them. Is the noise only generated by the lead edge of the blade 'cutting through' air? and different parts of it (...
3
votes
2answers
198 views

The heat equation in relation to smoothing algorithm

Recently I learned about a technique in image processing, which has its roots in something called the 'heat equation' from physics. The original creators of this technique were inspired by the physics ...
-1
votes
1answer
401 views

High frequency sound transmission through plastic. I can't hear enough treble! [closed]

I have a large cylinder made of a rigid thick plastic with a speaker inside of it. I want to be able to hear high pitched / high frequency noise from the outside but I'm primarily hearing bass. The ...
17
votes
2answers
2k views

Maximum delay for effective active noise cancelling?

Active noise cancelling reduces unwanted sound by sending the inverted phase of the original phase: (Source: Wikipedia) Theoretically, this seems logical to me. However, in real life, the anti-...
0
votes
1answer
87 views

Numb3rs TV series - Antenna

Most of you might have watched the TV series 'Numb3rs'. http://en.wikipedia.org/wiki/Numb3rs In one of those episodes they were discussing about how to capture the contents on the screen of a ...
4
votes
1answer
76 views

Do error checking costs of quantum computing shrink BQP?

BQP is the set of problems solvable in polynomial time for a given error tolerance, and it is suspected to be larger than P (and BPP, which is probably equal to P). However, inability for the gates to ...
1
vote
2answers
193 views

What is the fundamental reason for noise?

I have read that noise is a result of there being "no such thing as a perfect one-way valve". That energy transfer is never perfectly one-way; there will always (at some level) a finite flow of energy ...
0
votes
1answer
76 views

Noise is a form of dissipation?

(Mechanical) noise is a form of dissipation? For example, when the computer fan turns it produces noise. This noise is a form of dissipation in addition to heat produced by the machine (computer)? If ...
4
votes
1answer
317 views

total noise power of a resistor (all frequencies)

Let's calculate the power generated by Johnson-Nyquist noise (and then immediately dissipated as heat) in a short-circuited resistor. I mean the total power at all frequencies, zero to infinity... $$(...
4
votes
4answers
478 views

Friction at zero temperature?

By the fluctuation-dissipation theorem (detailed-balance for Langevin equation), $$\sigma^2 = 2 \gamma k_B T$$ where $\sigma$ is the variance of noise, $\gamma$ is a friction coefficient, $k_B$ is ...
0
votes
4answers
298 views

Isotropy and Noise

If you have a field which value is just Gaussian noise plus a constant do you call it isotropic? there is no preferred direction however it is not "the same" in all directions if "the same" means "...
5
votes
2answers
349 views

Modeling stochastic process with frequency-dependent power spectrum

I'm trying to model of Johnson-Nyquist noise propagation in a nonlinear circuit. An ideal (linear) resistor can be modeled very nicely by the Fokker-Planck equation (equivalently, the drift-diffusion ...
1
vote
2answers
85 views

Any noise slowly starting to take effects?

I am studying a system subject to random noise, or a system driven by some noise, for example, heat flow or wave propagation perturbed by noise. I would like to know if there is a real system where ...
1
vote
1answer
540 views

noise level (units confusion)

i had a question in one of my classes regarding SNR in underwater acoustic channels. There are a couple of terms with the unit dB re uPa. I know it stands for dB ...
1
vote
2answers
1k views

Noise amplitude increases as sample rate increase

I am testing the material properties of some very low stiffness materials. I'm using a force probe connected to software, sensing at about a hundredth of a gram of force. Now, what's interesting is ...
4
votes
1answer
2k views

Signal-to-noise ratio of the difference between two signals

Something tells me this must be a fairly simple question, but I have somehow been unable to find an answer to it. In short: I need to calculate the difference between two signals, A and B, each one of ...
4
votes
2answers
4k views

Decibel level addition of multiple noise sources

If I have four computer fans of which each is said to run at 46 dB, and they run close to each other, how loud is the whole system? I somehow recall from my physics course that 10 decibel ...
5
votes
2answers
2k views

Generating Pink Noise

I've generated some white noise in Excel by using the formula $$2*\mathrm{Math.RAND}()-1$$ I would now like to create some pink noise. I believe this is done by applying some sort of filter to the ...
3
votes
2answers
595 views

why isn't the variance of Fano noise proportional to the number of photon arrivals?

I've been reading "Photon Transfer" by James Janesick and in Chapter 3 (http://spie.org/samples/PM170.pdf) he describes the various sources of noise in a CCD. Basically, incoming photons interact with ...
2
votes
0answers
262 views

Schottky and shot noise

I am looking for a little history on shot noise: when was it first predicted and first measured? In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...