Noise Definition and 474 Threads

Hello physicsforums. What causes noise in electrical cables and/or transformers and/or electrical stations ? By noise I mean mechanical sound waves like bzzzzzzzz, not signal noise. And what is the proper way to search in google for this, I could not find a wikipedia article on this.

"White noise" energy vs. frequency components energy. White noise, I have learned that is a mixdure of all possible frequency components at the same time. All at the same levels. White noise can for example occour in resistors where an electric current flows through. If I filter it through...

Homework Statement I really need help with them all but I mostly have a question over the problems with noise margins or gain terminology. The problems are located here on tutorial problems under the digital abstraction it is the second one under tutorial problems. The problems can be found...

Let's say I have a wireless device, one that works on radio frequencies, let's say it's a remote control car that operates on 100ghz for example's sake. If I were to try operating this car with its intended remote, but then have a friend broadcast similar frequencies, I would obviously get some...

Hello. Say I have a given noise spectral density and I want to plot the random noise signal arising from this spectral density in the time domain. How can I generally accomplish this? For white noise, I would just pull numbers from a normal distribution, but I don't know what to do for non-white...

Hey guys, I'm working on some Current-Voltage data in excel. I need to do some analysis with the data, and the first step is to compute dV/dI. I have to do this in excel so decided to use excel's SLOPE function (5 point slope) to compute dV/dI. However, it seems that the derivative has a lot of...

Hi! My transmitter send a signal with BWsignal=17KHz.. The receiver has an antenna with BWantenna=30MHz... I work in a laboratory so T~300k.What is the Input Noice to receiver? P=KTBWeq=>-174(dBm/Hz) + 10logBWeq BWeq? what is this? What i will see in my S.A?it depends from the...

Hello :) I'm new to this forum, so excuse me for my straightforwardness ;) I'm working on my bachelor work and i can't find a solution. I'm writing about wind turbines' created noise dependence on temperature and pressure. So i came to this point, that i have measurements of wind speed, air...

Every time I walk by the electrical transformer at the end of the lane, I hear a low humming noise(≈50Hz) that is continuous. I have observed this in all types of fans. I grab the hub so that it is not able to rotate and switch it on. Then I hear this hum. When the mixer/grinder chokes, it...

I have a two way radio that I'm trying to control remotely through 120 ft of 25 conductor cable at 22 gauge. The radio uses serial communication between the actual transmitter and control head unit. After I wired the pin's up accordingly, there is to much noise pickup through the cable and it...

A 200mv peak to peak sinusoidal signal is applied to an ideal 12 bit A/D converter, for which Vref(v p-p full scale) is 5v. Find signal to noise ratio. This is a problem worked out by one of my lecturer and the answer seems to be 46dB. But I am confused on his method. Is there anyone who...

Hello, I'm a technical translator from Germany and urgently looking for a particular term: It describes a kind of case/protection around the gearbox which reduces noise emission. The German term is "Getriebekapselung" ("getriebe" = gear, kapselung = "protection/case/capsule?" Is...

This is a question about the proper form for thermal noise from a resistor. This is purely academic for me - I always work in the regime where \hbar \omega << k T so the noise spectrum is simply P \approx kT. When this no longer holds, quantum effects matter of course. Then I have seen...

Homework Statement Base station transmits signal t which is received by two antennas such that: x = h1t + n1 y = h2t + n2 where n1 and n2 are independent additive white Gaussian noise with variances σ21 and σ22 respectively. h1 is the channel gain between the base station and receive antenna...

This is an instant idea that I got right after i read an article about noise. Do you think it is possible to make an noise cancelling headphones by using the LM741. Except, i won't be amplifying the signal from the inputs (i can if choose to by just adjusting the varistor) but by using this op...

Hello, If there is a fixed noise like a faucet running, and I sit in a deskchair at a fixed location in an adjacent room, do you think it would be possible the build a program for either the desktop speaker (also fixed), or another computer somewhere else in the room which would cancel out...

I've been given the following homework exercise and I really need some help with part C. Question1. In figure 1. (attachment), an LR-lowpass filter is given with L = 120mH and R = 18 kΩ. This filter is characterized by the transfer function: H(f) = Vuit(F)/Vin(f) Determine the following...

Dear people, it might be a simple question, but I have been on this for over 2 days now and can't find a proper explanation of this anywhere: https://dl.dropbox.com/u/2264519/circuit.jpg Picture a RCL circuit which is kept at room temperature. Now even when there is no current going through...

how to purposely INDUCE EMI, noise, et cetera?? drill? phone? troubleshooting a GPU server, it has a card in it that generates a 20-100 MHz clock signal that goes to the actual GPU. Have worked on several of these units, when they fail the gpu doesn't get the clock signal so there is no VGA...

So I don't have a lot of noise theory background (or, really, any) and I'm having trouble with this. I'm hoping someone can expalin and/or point me to some good resources for looking these things up (I have access to a good academic library, so I should be able to get any not-too-obscure...

I have a vector signal, \underline{x}(t), which is afflicted with Gaussian noise \underline{n}(t). I take a finite number, L, of discrete observations and (based on those observations) want to determine whether: (1) Only Gaussian noise is present, \left[\text{i.e. } \underline{x}(t) =...

I work with industrial electrical system and I got a question regarding electrical noise caused by electromagnetic radiation. In an industrial environment, cables carrying an analog signal are shielded and its drain wire is Earth grounded at one end of the cable. When electromagnetic radiation...

I am designing an eeg circuit and planning to do an adc for it. Since the eeg requires a band pass filter I am planning to use a second order low pass bessel filter in it. Suppose I want to reduce the noise ( as I am working with low frequencies ) and increase the efficiency of the circuit...

Can anyone recommend a source of information that quantifies how wind shear effects the propagation of sound/noise? I know the basics in that wind shear either bends sound waves upwards or downwards but I'm looking for something that helps calculate the effect.

I'm writing a story that takes place at about 200 AU from Sol - it's outside the heliosheath, where solar wind and interstellar wind meet. We haven't managed to send any spacecraft that far out yet, though Voyager 1 and 2 will get almost that far before they run out of thruster fuel and...

Hello, In experiments such as KamLAND, it is expected to measure neutrinos emitted by Japan's nuclear reactors. Such experiments were built to find evidence for neutrino oscillation. Is there anyone who knows how one can make the difference between the neutrinos from nuclear reactors and...

Is there some fundamental fact of the universe (Quantum Mechanics) that prevents us from removing noise (without having to compare the entangled particles)? In the quantum eraser experiments: To get ("un-embed") the interference pattern i.e. to separate the entangled particles from the...

Citizens of Physicsforums. I would greatly appreciate your advice. I've been wrestling with a pesky noisy phototransistor for quite a long time, and am at wit's end. The sensor is being used to transuce an audio signal in the 1-5kHz range. Unfortunately the shot noise is introducing...

Hello Everybody, I'm trying to plot the frequency spectrum of RIN using Matlab. I've the following code function p=rateblock tau_s = 3e-9; N0 = 1e24; A =1e-12; P0 = 1/(A*tau_s); TSPAN = 0:1e-2:10.23;; Y0 =[0 0]; [T,Y] = ODE45(@rate_equation,TSPAN,Y0); subplot(2,1,1)...

Hi, I am making a capacitor with Aluminum plate and Mylar film. Al plate surface has tiny groove arrays, each groove forms a cavity and the mylar film is sitting on top of the groove to allow its vibration under input AC voltage. I am putting in AC of ~300Vpp with frequency of 60KHz. The AC...

Hi, I am a biologist and I do a lot of experiments on cellular electrophysiology. I keep my preamplifier and the biological subject inside a Faraday cage, and it works well. In some experiments I need to deliver a drug to the cell so I have to enter the cage briefly, with my hand only, and...

I have assembeled one smps circuit for 25volts, 40 amps. Circuit gives unwanted high feaquency noise at part load. It is silent at no load. What could be the problem. I am not electronic engineer, Electronics is my hobby. Any body can help me.

Can light affected be affected by noise as other signals? I am not able to figure it out..if I am amplifying the light using some optical amplifier,will there be any effects of noise in it? Regards zakee

Hi there, I want to modify a equation which is written for Singal to Noise Ratio. Now I want to change for logical interference. But I could not find any reliable source of explanation, " [FONT="Arial Black"]what is the relation between SNR/SINR and interference(Logical/Physical)?"

Hi all, I got an idea why noise is having a gaussian pdf but didnot understood why it should be having zero mean. Why can't noise contain a dc content. -Devanand T

Hi all. I have been recording the thermal noise produced by a number of resistors. I have created a excel sheet that takes the readings from the 8 1/2 DVM and performs a FFT on them, in order to give me the frequency domain plot. However I am not 100% certain of what I am seeing because of my...

I've been trying to figure out how to get the signal to noise ratio of a completely multiple choice type exam. I can't do it and it's driving me nuts, so finally I found this website and decided I'd ask. :D Say you let your students take a multiple choice test and you are able to get all...

For about the 7th time I've been told the story of how Penzias and Wilson discovered a noise the source of which they could not detect. It turned out to be the CMB. Well, why should the cmb make a noise? It's just photons in the microwave spectrum.

Hello, I've been trying to find the answer to this question on the internet but no real luck so here goes: Imagine a signal My_signal which has two components, the actual signal A which is not constant over time and a noise component, we can call it N, where said noise component has a standard...

Hi I have stumpled upon the following expression for the correlation function of the photocurrent shot noise for a photodiode <\delta i(t)\delta i(t+\tau)> = \frac{e^2\eta}{h\nu}P\delta(\tau) where η is the quantum efficiency and P the power in the signal. δ(τ) denotes the Dirac delta, which...

Langevin equation describes the brown motion. But I don't understand the nose term η(t) in the equation. What's the relationship between η(t) and the force proportional to the velocity due to stoke's law? I mean they both belong to the force between the collisions with the molecules of the...

I'd say about every 15 minutes or so, a faint beeping noise is coming from my computer. It's really hard to tell where it's coming from, but I'm pretty sure it's my computer. I shut down my computer last night and I believe I heard it in the middle of the night. So I'm thinking it's my power...

Hey guys, If I wanted to go about generating just a plain noise signal (don't care what the signal consist of), at a certain frequency (say 10 MHz) what is the best way to go about doing that? If possible I would really like to use a microprocessor or ARM processor (due to the higher...

Hi, I have a pretty simple question which I thought I do not need to make a topic about, but Google is actually not helping, which is surprising. So here it goes: How can white noise have infinite power if its variance is finite? As far as I am aware, the following is always valid for a...

I'm asked to get the noise signal from the constant current source I built with a 741 Op-Amp. I know I have to read it from the scope, but how do I go about the connections to the scope, and what other procedures must I follow to read the noise contribution? Pls refer to the figure provided in...

I have a situation where I see spikes (with ringing) on the output of DC power supplies whenever something AC powered is switched in the room. The spikes change in magnitude; they can be as bad as 3 volts peak-to-peak; I suspect they change "randomly" because they are related to when the device...

I have a power source that is supposed to be low noise, and i want to verify that the data the company sent me is indeed accurate. In order to do this, i want to reproduce their graph showing current noise density (nA/root(Hz)) on the Y axis, and Hz on the X axis. I am an undergraduate physics...

I have a device (fNIRS, though knowledge of fNIRS probably isn't necessary to help) which produces very noisy signals and a noise reference. The noisy signal consists of a combination of a desired signal, and a noise signal, which is a scalar and phase shift of the noise reference. However, I'm...

Is there any circuit for generating Gaussian Noise with a mean and variance. we should have control to change mean as well as variance accordingly. thanks.

Hi I have read the following online (http://tf.nist.gov/general/pdf/1819.pdf): "Regardless of the application, the basic goal of locking the frequency of a laser to a cavity is to reduce the frequency fluctuations between the laser and cavity. The noise spectrum of the laser’s frequency...