Noise Definition and 503 Threads

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. cepheid

    What causes the feedback (a noise increasing in intensity and pitch)?

    What causes the feedback (a noise increasing in intensity and pitch) sometimes heard when people speak through microphones? I'm sure I have enough background to understand an explanation, I've just never thought about it before.
  2. P

    Can i exploit johnson noise to violate the second law?

    Thermal noise known as “Johnson noise” or “Nyquist noise” is well known and characterized. This noise is a result of thermal agitation of charge carriers inside a conductor. Its power spectral density is given by: v^2=4kTRwhere kB is Boltzmann's constant in joules per kelvin, T is the...
  3. J

    Eliminating AC Line Noise in Your RFID Circuit: Tips and Tricks"

    Hello, I'm designing a circuit with a linear regulator to supply power to an RFID reader. The input to the regulator is 12VDC supplied by an ordinary external AC/DC desktop switching power supply. When I look at the output of the linear regulator with a scope it looks pretty clean except for...
  4. C

    Applying physics against a noise problem

    Hi, first of all, excuse my very poor englishI have a big problem with a bar in front of my window, in the middle of a little park. They close very late (ignoring the closing hour stablished by the law) and they make a horrible noise. Here (in Spain), there is very passivity applying the...
  5. S

    Buzzing Noise From Laptop Speakers

    Hi, whenever i play sound using the laptop speakers i get a buzzing noise which gets louder with louder sounds. It sounds like a motor (but i couldn't hear anything loose rattling about) anyway when i plugged in some speakers the sound was fine and when i took them out the buzzing was still...
  6. J

    Exploring Noise Cancellation and the Dissipation of Energy in Sound Waves

    Noise cancellation through interference; I guess most people here know what I am talking about. My question is: where does the energy go? In a (sound)wave there is constant exchange between kinetic and potential energy, or at least that's how I see it. Now the wave gets canceled...
  7. R

    How to Calculate the Readout Noise of a CCD?

    CCD readout noise problem! Hello all! does anyone know how to calculate the readout noise of a ccd? i have found values for proffesional and amateur ccds on the net but as far can't find any method of calculation. what does the value depend on? charge transfer time? number of electrons...
  8. H

    Noise handling algorithm in 8 wire touch screen

    Noise handling algorithm in 8 wire touch screen here's how a touch screen work http://focus.ti.com/lit/an/slaa298/slaa298.pdfProblem: when the touch pen is stationary on a point and reading ADC values from a touch screen using the micro controller, the ADC values are never the same eg, 1st...
  9. D

    Is Finding Nemo Worth Watching Without Dorie?

    I just watched Finding Nemo, I don't like Dorie !
  10. L

    White noise in communication channel

    hi all - its been very long - hope everyone is well! just a data comms related question: When modelling a communication channel we normally include AWGN, that is, Additive white gaussian noise. Can anybody tell me why we use white noise in the model. I know it has a constant power...
  11. V

    Improving Noise Reduction in Airbus Engine Nacelles

    This may be of interest to readers: http://www.flightglobal.com/articles/2007/01/23/211641/airbus-a350-xwb-set-to-be-quietest-generation-of-airliner-as-manufacturer-improves-zero-splice.htm A noise reduction engine nacelle intake. "A zero splice liner with a continuous surface and lacking...
  12. Math Is Hard

    What Does the -1.0 to 1.0 Range in a White Noise Graph Represent?

    What is represented by the -1.0 to 1.0 range of this graph? Four thousandths of a second of white noise: http://upload.wikimedia.org/wikipedia/en/thumb/5/55/Whitenoise.png/350px-Whitenoise.png I am not sure what I am looking at. It's from: http://en.wikipedia.org/wiki/White_noise
  13. N

    Noise reduction and square wave/sine function question

    I have two simple questions but I'm not 100% on how to get the correct result. 1. "The noise is reduced by 6 dB" means its amplitude is cut to _%? How is it calculated to 50%? I try 20log(Av)... 2. Does this wave contain 30k hertz sine function? (see attachment) The answer is yes, but I...
  14. U

    Can You Combat Johnson Noise and Shot Noise in Instrumentation?

    I was wondering if someone could give me some ways to combat Johnson noise and shot noise. Thanks
  15. N

    Noise in 7-10.5 kHz Range: Solutions Needed

    Hi all, I have a high gain current to voltage amp connected to 2-3 meters of coax which is picking up noise in the 7-10.5 kHz range. Does anyone have any expereince in waht could be the source of this noise? Right now I'm using a couple op-amps and a low pass filter to get the noise to a...
  16. S

    Noise Reduction System: Preemphasis/Deemphasis Filter

    I know that purpose of the preemphasis filter in a noise reduction system is to increase the amplitude of the input signal at frequencies where SNR is low prior to transmitting the signal. I also know that a deemphasis filter is located at the receiving end and its purpose is to undo the effects...
  17. S

    Mathematica Adding Random Noise to a Sine Wave in Mathematica

    For my time series and spectral analysis class i need to graph something like in the attachment. i need to have 100 numbers that are connected like that, and then 'add' them to a sinusiodal wave to create a real life wave - with noise. How would i do this using mathematica?? I can easily...
  18. A

    Pullup Resistors & TTL Gates: Reducing Delay and Noise

    Is it true that a "high" input of a TTL gate shouldn't be left floating but instead connected to +Vcc through a pullup resistor because this way the propagation delay time is reduced and less noise is captured? If that's true, should a pullup resistor be used when connecting the input of a...
  19. DaveC426913

    Plumbing Home project: noise insulating a pump while keeping cooling

    Please move to appropriate forum if necessary. I need some help. Attached is a pic of my standard 1/4hp Hayward pool pump. I want to enclose it to make it quieter. (The sound is being transmitted by air rather than by physical contact.) As a "proof of concept" I stuffed it in a storage bin...
  20. B

    Solving Noise Problems: All You Need to Know

    Dear Sir or Madam I have some troubles regarding the noise subject. Would you mind to help me solving the following problems? Thank You. 1. Under what condition will sound power level be lower than sound pressure level? 2. L10, Leq, Lmax ~ How are they related to noise fluctuation and...
  21. D

    White Noise vs Black Noise | Difference Explained

    Hi all I want me to explain what white and black noise is .And what's the difference betwween them?
  22. P

    Hearing outside noise while in an encolsed room

    The theory is that sound is heard because of fluctuations in the air molecules that surround us but why is that we can hear noise coming from outside when we are in an enclosed room? Is it the case that air molecules are able to travel through the walls of an ordinary room?
  23. M

    Magetic contactor humming noise

    Hello. The ac contactor with two magnets sometimes give a noise.For some contactors humming is more audible.What are the possible causes of humming. Also what is the effect of humming on performance of contactor.Can anybody help on this subject?
  24. J

    How Can I Design a Low-Noise, High-Gain Precision Amplifier Circuit?

    help! with building a circuit. i need a gain of 300 (not exact, but somewhere around there, 200-500) for a small signal (typ. 0.1mV to 5mV) AC input with a bandwidth from 0.5Hz to 120Hz. I need it low-noise, with high precision and reliability... has anyone got a reference for any sort of help...
  25. M

    Solving Mouse Noise Problem on Windows XP

    My mouse is causing noise in my speakers whenever I move it. I can't exactly explain the noise, but it's quite and wouldn't be noticed if perhaps the television was on or I had an mp3 playing. I tried muting the speakers from the volume control panel in windows XP, but I could still hear the...
  26. K

    Does Wood Create Noise When Vibrated?

    My question is quite simple: It is common knowledge that most metals make a lot of noise when in contact with moving/vibrating parts. Some examples are the hood of your car, or a computer case with fans on it. Does wood have the same characteristic? I want to use wood to mount a few fans...
  27. G

    MATLAB Reducing Noise from Matlab Generated Square Wave - SNR 0dB

    I posted the details of myquestions earlier but no help. Maybe I need to rephrase it. I basically generated a square wave and added noise to it using Matlab. The question is how do I design a filter to reduce as much noise as possible to retain most of the square wave. The SNR is OdB...
  28. G

    MATLAB Filtering Gaussian noise with Matlab

    I’m generating a 1 kHz square wave and adding Guassian noise to obtain a SNR of 0 dB (using Matlab6.5). The task is to design a filter that will filter out as much noise as possible from the square wave plus noise signal. The sampling frequency is 100kHz. Noise signal: 100.0*randn(1...
  29. M

    I need to measure a noise. i need the volume and frequency.

    my a/c-heater unit thing in my dorm is making this very irritating high pitched noise. maintenance can't hear it. so i need to prove that it's there (this is important because i live in a 12 month dorm and will be here this winter). are there any programs or devices that will measure frequency...
  30. F

    What is the circuit for the Polyfusion Noise Generator?

    i was wondering if anyone could explain the circuit at he following link http://www.synthfool.com/schematics/polynoise.gif
  31. F

    Circuits for all noise generator

    i am trying to find a circuit diagram for a noise generator that can change between all the colours of sound. it is driving me made and was wondering if anybody can help please
  32. B

    White Noise Generator: How Does it Work?

    Hi guys I'm currently working on a university experiment trying top create acoustic crystals. We're using a white noise generator to generate sounds at all frequencies. However I'm unsure exactly how a white noise generator creates the random signal. Can anyone explain how the an analogue...
  33. DocToxyn

    Is 115-120 dB Loud Noise Harmful to Dogs and Humans?

    I've been watching a discussion on another forum regarding the use of loud horns to deter dogs from chasing bikes. Some dissenters say that it is cruel since dogs can "hear so much better than humans" and such loud sounds can injure them. My question is, is it better stated that dogs have a...
  34. I

    The Effects of Brown Noise on Sleep Quality

    How loud does brown noise have to be for it to be effective?
  35. S

    Noise on Passenger Jets: Surprising to Sleep-Seeking Flyers

    what are all that noises on passenger jets when flying with full load of passengers ? I thought it going to be really quiet on board but there is so much noise that one can't hardly sleep on board.
  36. O

    Definition of dynamic noise and observational noise in finance

    Hi, i have problems differentiating these two terms. can anyone give some examples of these two terms? Thanks!
  37. C

    Exploring Galaxy Surveys: Shot Noise Estimation

    I am reading about galaxy surveys. I want to know what is shot noise ? how we estimate it into real and Fourier space ? I am basically reading astro-ph/0503603 & astro-ph/0503604. I am not able to solve exercise 4, 5, 6. I will be thankful, if anybody can provide me some reference.
  38. C

    Noise vibration harshness(NVH)-fea

    What do these terms mean. I am doing static analysis using fea on some parts. But what do automotive people do in NVH. Please give examples
  39. S

    Building a noise detecting circuit

    Hey, I never used to like electronics, but after doing a unit last semester it has really interested me. I've gone out and bought simple circuit components and have built a whole heap of simple circuits just because I wanted to learn more of how things behave. Anyway I still have the notes...
  40. W

    Process noise of satellite orbit determination

    During my work of space vehicle orbit determination, I have been confronted with a difficulty that hasn't been solved until now. When calculating the transition matrix that translate the process noises to the state parameters of position and velocity,how can I work out the partial derivatives of...
  41. W

    Problem of process noise of satellite orbit determination

    During my work of space vehicle orbit determination, I have been confronted with a difficulty that hasn't been solved until now. When calculating the transition matrix that translate the process noises to the state parameters of position and velocity,how can I work out the partial derivatives of...
  42. B

    Cancel Microphone Noise w/ Lowpass Filter | Help Needed

    I need help in cancelling microphone noise... I am just not sure whether or not i should use a lowpass filter... can anyone give me help? i want to use the filter command along with fir1... but i don't understand how to use them... i couldn't figure out how to customize the filter...
  43. M

    Troubleshooting Computer Noises: Is Your CPU Temperature to Blame?

    My computer makes an ambulance like noise every 5 or ten minutes. Any idea what this could be?
  44. L

    What Are the Best Materials for Reflecting Low-Frequency Sound?

    Active/Passive noise control hi everyone, I am currently working on a project to reduce noise in AC/Heating systems in airplanes. As reference am using some literature in Engineering Noise Control and some research papers on Active/Passive noise control. I am currently searching for some...
  45. L

    Which Materials Reflect Low-Frequency Sound in AC/Heating Systems?

    hi everyone, I am currently working on a project to reduce noise in AC/Heating systems in airplanes. As reference am using some literature in Engineering Noise Control and some research papers on Active/Passive noise control. I am currently searching for some information on; if there are...
  46. Mk

    How does loud music and noise affect hearing?

    Well, you know the question. :smile:
  47. Ivan Seeking

    Making noise over the [Kokomo] hum

    http://www.indystar.com/articles/2/133270-5162-009.html
  48. N

    Noise reduction in a jet engine

    I am in the process of writing a report on the Physics of Jet engines and I have come across a problem I cannot comprehend. In the exhaust of many jet engines they allow the atmospheric air to mix with the air from the engine to reduce exhaust noise. From what I understand this allows the...
  49. D

    K-Delta Function in Autocorrelation of Gaussian White Noise

    hi, I would like to know why dirak-delta function is used in autocorrelation in a way that the following is true: <å(t)å(t')>=2Dä(t-t') where å(t)is Gaussian white noise and D is the strength of the noise. Dora
  50. S

    Poisson stats: signal to noise

    A star was measured to have an apparent magnitude m=16 with S/N=10 integrated over a minute. What is the uncertainty in the measurement? signal=flux*area*time noise=sqrt(signal)=sqrt(fAt) So, S/N=sqrt(fAt) How can I find fA? m=-2.5logfAt+K 16=-2.5log(fAt)+K Hoping that K is arbitrary...
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