What is Noise: Definition and 501 Discussions

Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, noise is indistinguishable from desired sound, as both are vibrations through a medium, such as air or water. The difference arises when the brain receives and perceives a sound.Acoustic noise is any sound in the acoustic domain, either deliberate (e.g., music or speech) or unintended. In contrast, noise in electronics may not be audible to the human ear and may require instruments for detection.In audio engineering, noise can refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as a hiss. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting.In experimental sciences, noise can refer to any random fluctuations of data that hinders perception of a signal.

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  1. bhanesh

    Thermal Noise Voltage of 3 Resisors in Series

    What is thermal noise voltage of three resisors connected in series
  2. J

    Indoor vs Outdoor Stadium noise levels

    There's been a lot of headlines in sports lately about record breaking noise levels. The Seattle Seahawks home stadium broke the outdoor stadium noise record at 137.6dB (the previous record is from an outdoor stadium as well). The indoor stadium noise record is 126 dB at the Sacramento Kings...
  3. J

    Noise & vibration in condo - HELP

    Noise & vibration in condo - HELP! Hi there, I just bought a newer condo (5 years old) and have noise and vibration coming from the mechanical/boiler room located on the first floor beneath my unit. The property manager has had a plumber come into put dampeners on the pipes, and moved the...
  4. F

    Unraveling the Mystery of N_{0} in PSD of Noise

    I know the power spectral density, PSD, of noise is: \frac{N_{0}}{2} from where do we get N_{0} ? Is that the RMS value of the noise? Is it related to noise power and noise temperature as in the following: N=kTB, where k = Boltzmann’s constant, T is noise temperature, and B is...
  5. L

    Troubleshooting Strange Noise from 250kw 3 Phase Motor

    Hi guys I have been testing a brand new 250kw 3 motor wired in delta. I have it connected to a 170 amp vfd with no load for testing. It draws 105 amps at 50hz and is balanced. Intermittently the motor makes a strange that i have not heard before. It sounds like a spoon taping another...
  6. D

    Active Noise Cancellation for Conference Room

    Hi! I am currently trying to find a good Active Noise Cancellation System for a conference room that we are currently designing. The room is 26' l x 14'-8" w x 9' h. One long wall and one short wall are made out of STC 55 gypsum board and have acoustic wall panels; the other short wall is...
  7. P

    Electrical noise ( I mean sound waves )

    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.
  8. Low-Q

    White noise energy vs. frequency components energy.

    "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...
  9. D

    Noise Margins & Gain Homework Help

    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...
  10. B

    How do wireless devices eliminate noise?

    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...
  11. D

    Time domain noise from spectral density

    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...
  12. J

    Getting rid of noise in derivative?

    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...
  13. MathematicalPhysicist

    White noise going through a Hilbert filter.

    Now, assume I have a white noise, n(t)\tilde \ N(0,1), i.e gaussian with zero mean and variance 1, and it goes through a Hilbert filter, i.e we get: $$ \hat{n}(t) = \int_{-\infty}^{\infty} \frac{1}{t-\tau} n(\tau) d\tau $$ I read that \hat{n} should be also a gaussian, because this is an...
  14. F

    Receiver's Noise Input =K*T*BWeq ?

    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...
  15. X

    Wind Turbine Noise Dependence on Temperature & Pressure

    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...
  16. PhysicoRaj

    Humming Noise in Electrical Transformers and Appliances

    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...
  17. A

    Serial Communcation Conversion / Noise Coupling

    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...
  18. D

    Signal to Noise ratio calculation

    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...
  19. T

    Gear Noise Protection - Getriebekapselung

    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...
  20. J

    Zero point energy in thermal noise spectrum?

    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...
  21. madmike159

    LTE SIMO signal to noise ratio

    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...
  22. A

    Noise cancelling device, making one

    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...
  23. E

    Building A noise cancelling program.

    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...
  24. G

    Find L such that 70% of the noise power is dissipated in R

    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...
  25. J

    Thermal Noise in Electrical Circuits

    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...
  26. hxtasy

    How to purposely INDUCE EMI, noise, et cetera? drill? phone?

    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...
  27. Q

    Comparing NEP and noise temperature?

    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...
  28. W

    Binary Detection in Gaussian Noise

    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) =...
  29. D

    Electrical Noise: Shielded Cables & Earth Grounding

    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...
  30. R

    Will increase in order bessel filter in any way contribute to noise?

    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...
  31. C

    Effect of wind shear on noise propagation

    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.
  32. S

    Question about Heliopause / radio noise

    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...
  33. P

    Detection of neutrinos from nuclear reactors vs. ambient neutrino noise

    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...
  34. S

    Does QM itself prevent removal of noise without comparison

    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...
  35. M

    How Can I Reduce Shot Noise in a Phototransistor Audio Application?

    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...
  36. M

    MATLAB Calculate Relative intensity noise using laser Rate equations matlab

    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)...
  37. M

    Calculate Relative intensity noise using Rate equations

    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)...
  38. X

    Troubleshooting a High-Frequency Noise in a Capacitor

    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...
  39. A

    Noise when entering Faraday cage

    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...
  40. S

    High frequency noise in smps transformer

    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.
  41. L

    What is the equation for calculating signal-to-noise ratio in astronomy?

    Homework Statement You observe a star with a count rate of 0.1 counts per second and the background is 0.05 counts per second. (a) How long do you need to observe for in order to detect 100 counts from the star? [2] - 1000 seconds (b) Estimate the signal-to-noise reached in the exposure...
  42. Z

    Can light affected be affected by noise as other signals?I am not

    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
  43. D

    2-D Brownian motion with correlated noise

    dx/dt = η(t) dy/dt = ζ(t) where <η(t)>=<ζ(t)>=0 <η(t)η(t')> = 2Dδ(t-t') <ζ(t)ζ(t')> = 2Dδ(t-t') If <η(t)ζ(t')> = 0, we have the standard 2-D diffusion equation and the analytical solution is known. If <η(t)ζ(t')> = 2Dδ(t-t'), or η(t) = ζ(t), we can transform it into a 1-D problem...
  44. M

    Relation between Signal to Noise ratio and Logical Interference

    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, " what is the relation between SNR/SINR and interference(Logical/Physical)?"
  45. dexterdev

    Why do we consider zero mean for gaussian noise in a communication channel?

    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
  46. J

    FFT and Resistor Noise Newbie Questions - PLEASE HELP

    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...
  47. C

    Calculating Signal to Noise Ratio for Multiple Choice Exams

    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...
  48. S

    Signal to Noise ratio and exposure time question

    You obtain an image of a 7 magnitude star in a 1 minute exposure. You found that the 7 magnitude star was detected at S/N = 10 in the image. The S/N was too low for your science and you decided to take another image. If you want to obtain a 1% photometric result on this star, what should be the...
  49. G

    Why does the cosmic microwave background make a noise

    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.
  50. F

    Standard deviation for a signal with a noise component

    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...
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