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. V

    Autocorrelation of white noise.

    I'm stuck with an elementary thing, it must be something obvious but I can't see what's wrong. Here it goes. I was writing up some elementary course material for an instrumentation course, and wanted to quickly introduce "white noise". Now, the usual definition of white noise is something...
  2. J

    Mathematical Analysis of Random Noise + Stephen Rice

    Does anyone know where I can download the article Mathematical Analysis of Random Noise by Stephen O Rice for free ?
  3. U

    How to filter noise from an inductive pickup. low pass filter.

    i am making a tachometer which will count pulses from an inductive pikup connected to an HT lead on an engine. i am having great difficulty when measuring my signal from the pick up as there is a huge amount of noise. can anyone raccomend the best way to clean this up? someone mentioned an...
  4. Topher925

    Optimizing Data Filtering Techniques for Removing Gaussian Noise in ADC Readings

    I have a circuit that is outputting a good solid analog signal which is being read by an AD converter. While the signal is good and noise free, the ADC is not and is adding a lot of gibberish to my signal which is being sent to a PC. As of now I have tried using a simple discrete kalman filter...
  5. J

    The noise of a muted television

    I have noticed that the television makes a very high pitched noise. You almost can't tell your hearing it until it is turned off. It is kind of like the ringing of the ear in a way. Then When I turn on the DTV box, the sound becomes a little louder and changes frequency. Does anyone know...
  6. Y

    Source of synchotron radiation causing galactic background noise

    Hi guys, I understand that in the Sun electrons are released upper chromosphere and corona which causes synchotron radiation when they spiral through its magnetic field, but how does it work in the galactic centre? Could anyone shed some light on this? What I mean is what's the constant...
  7. A

    Variance of the position noise

    Hi, I read an article in Kalman filtering. There is an example in introductory Mechanics. I just can not understand which formula for calculating the variance and covariance is used. The example is about a vehicle that is traveling straight on the road: The postition is measured with an...
  8. E

    MATLAB Adding Signal and Shot Noise in MATLAB - MB's Question

    hello well I have 2 vectors in MATLAB each representing a signal+shot noise. I have to add them. Can anyone tell me what the signal noise ratio will be when they are added? thanks MB
  9. R

    Solving AC Noise in Fuzz Box Bass Guitar Circuit

    I'm working on a 'Fuzz box' for a bass guitar, ckt diagram below. With fuzz on and gains up, I'm getting a strange (to me) AC artifact -- Oscope images below (AC waveform from isolation xfmr at 10V/div, signal out at 2V/div). With fuzz on, and the input shorted to ground, the artifact is...
  10. L

    Doom Character's Infamous Scream Noise

    From the PC game doom, one of the characters make an insane screaming noise that is reused in some movie, i can't think of it now. I haven't played doom in a while, but i really need to know where i can find this scream noise because it is the single most disgusting noise in the world. if anyone...
  11. R

    Extended Kalman Filter - Process noise and covariance

    Dear all, I'm trying to implement an Extended Kalman Filter for position, velocity and orientation tracking of a rigid body and I am using quaternions for representing the orientation in the state vector. As this is the first time I have to work with a Kalman Filter, and the project is on a...
  12. F

    Electrical dark, and spectrum noise.

    I don't mean to violate any rules or conventions; these are questions pertaining to labs I'm doing as part of an undergrad degree. It's not homework, as such, so I've not put it in one of those forums But my apologies if this is incorrect. Anyhow; the experiment that bothers me is a...
  13. A

    Thermal Noise (Johnson–Nyquist)

    Could someone explain the equation describing Thermal Noise? The equation is given by \overline{\left(\delta U\right)^{2}_{kT}} = 4RkT\Delta f Specifically I don't understand what the \Delta f is. Some online resources describe \Delta f as: - "frequency bandwidth within which...
  14. L

    What Causes Noise in Photomultipliers?

    does anyone know what causes noise in photomultipliers or where it comes from?
  15. C

    Why is noise always assumed to be Gaussian in noise-based applications?

    hi i want to know why while dealing with any noise based application noise is assumed to be gaussian distributed? give me the explanation clearly please
  16. I

    Further noise reduction techniques ontop of Savitzky-Golay FIR filter

    Hi PF Designers, Wasn't too sure if this would belong in the Electrical engineering forum but here goes. I'm designing a prototype for my thesis that will read in sensory data wirelessly to a MATLAB script. This sensory data is riddled with noise, however important data is contained in...
  17. D

    Atom Rubbing Sounds: Wood vs Glass

    What makes the noise when atoms rub each other. E.g a different noise is made from scratching wood than a noise from scratching glass.
  18. V

    Why am I hearing audible noise from my SMPS?

    Hello, I'm a newbie for this forum, and I don't have much practical experience on SMPS too. I found this forum when I'm searching for my solution from internet. My Circuit: I'm using a simple buck converter: Vin: 24V Vout:3.3V Iout: 1.5A (dynamic load) The loading is running in PWM...
  19. P

    MATLAB Matlab-compute the distribution of the noise signal

    my professor gave me this equation to compute the distribution of the noise signal but I have no ideal what it is, so can someone explain this for me 1/√(2πσ)*e^((x-μ)^2/2σ^2 ) thanks
  20. L

    Bayesian Inference for Determining Data and Noise Variance in Image Denoising

    Hello, I am working do determine an optimum threshold for wavelt transform image denoise. I have the following quesstion. considering a vector of a data d*: d*= d + noise where the noise is zero mean and with variance sigma ~(0,sigma) and the signal "d" has variance...
  21. T

    Building a low noise isolated PSU

    Hi there, For a personal project of mine, I have been designing a low-noise linear power supply to provide power to guitar effects pedals. A couple guitarists I know use a hodge-podge of AC adapters and switched PSU's to run their various pedals (sometimes 8 at a time). This mixture of...
  22. G

    Filter out Gaussian noise from data curve

    What is the best way to filter out Gaussian noise from points in a data curve? (i.e. each point of the x-y-graph is displaced in y by a random amount) A simple running mean does it, but on the other hand it also changes the shape of the underlying real curve. Is it possible to use the...
  23. W

    What can I do to cancel the noise?

    Is there any way I can build/make something that I can wear that prevents me from hearing what's going on around me? When I study, there are so many noises because of vehicles moving downstairs, TV on loud etc. What can I do to cancel the noise?
  24. E

    Troubleshooting Audio Noise in SMPS at 50KHz: Tips and Solutions

    I have a problem with my switch mode power supply, smps. It creates audio sound when I power it up, especially at minimum load. As I increase the load then sound disappears and in some designs it is still there. I don't know what to do. It is a bottleneck for me. Anyone who knows what to do...
  25. F

    EKC during a stress test; noise filtering

    Muscle noise is a big problem with our EKG machines at work. Even the slightest movement will overwhelm the waveform being studied; however, EKGs are done during stress tests which involve quite a bit of vigorous exercise. Muscle noise has a different waveform, but it's basically the same...
  26. C

    How do I reduce noise of the output voltage?

    yellow line: output of photodiode which detects an LED blue line: output voltage to the LED newfile1: the file without measuring using average of the scope. newfile6: the file with using average of 32 times of the scope. How to filter the noise? It's noisy, I find it's ok to use...
  27. J

    Would metal hitting metal or metal hitting glass make more noise?

    If you have a lump of metal would it make a louder noise if it hit glass or metal?
  28. C

    Uncovering the Randomness of Thermal Noise and Nuclear Decay

    1. Is thermal noise truly random? By truly random I mean can you not predict the next value even if you knew everything permitted about the electrons producing the effect. Does this follow from the math of quantum physics? 2. What about nuclear decay is it truly random?
  29. J

    MATLAB Does a function exist (prefferably in matlab) that finds a function in noise

    Does a function exist (prefferably in matlab) that finds a function in noise Cheers
  30. M

    Common mode noise and balanced detectors

    I'm working on a laser interferometry system that uses a pair of balanced photodetectors to record the signal. Each detector is on a separate port of a beamsplitter cube, and as a result receives (in theory) the SAME signal. The rationale for using the balanced detectors is that "they reject...
  31. U

    How Is Non-Gaussian Noise Calculated in Stochastic Processes?

    Dear friends,I have a question about non-gaussian noise as follow: R(t) is a white noise and Y1,Y2,Y3 are three uncorrelated Gaussian Variables with average 0 and standard deviation 1, so that Z_{1}=\int^h_{0}R(t)dt=h^{1/2}Y_{1}...
  32. J

    Tektronix 2246 Oscilloscope CRT Sparkle/Noise - Normal?

    Hello everyone. I am new and have a question. I just got a Tektronix 2246 Mod A Oscilloscope. Everything works great on it. The CRT seems to have some "sparkle" or "noise" in it. It is very slight and it is visible both on the traces and the readout. It looks like the traces and readout...
  33. T

    Detecting the existence of a sound that has been lost in thermal noise

    ultra sensitive microphone or technique for listening to inner ear A friend has very loud tinnitus. He says it is constantly louder than anything else he can hear. Nothing can be heard by an independant observer such as myself, but it is possible that a sound with a small power level is so...
  34. J

    MATLAB Clean Wave File Impulse Noise with Matlab

    I'm attempting to clean impulse noise from a wave file in matlab. the file is two channels, about 7 million points in each channel. What I wish to do is keep points, that are below my trigger levels, and delete points (in both channels simultaneously) that are above the trigger levels for either...
  35. G

    Blocking Out 100Hz EMI in the Lab

    Hi, I am using a simple circuit in the lab which detects current flow from an ion source. These are transient signals recorded at a rate of 100Hz. The problem is, the ion source is switching at the same freqeuncy at very high voltages. Needless to say there is a fair bit of 100Hz EMI. So...
  36. Math Is Hard

    Signal, noise, and, unequal variances

    I have two overlapping Gaussian distributions. One for probability of a noise event, one for probability of a signal event. My noise distribution has mean = 0, variance = 1, and standard deviation = 1. My signal distribution has mean = .80, variance = 3, and standard deviation = √3. My...
  37. T

    Overcoming Unwanted Apartment Noise: A Guide

    Do you have a constant noise in your apartment due to air conditioner for the building or nearby building? If so how to you get over it?
  38. P

    : Finding the Right Electronic Noise Retardant for Your Dyno Room

    Hi The company I work for has a Dyno room for tuning its engines before sale. Can someone advise me on an electronic noise retardant please? The room where the Dyno is situated is quite small and doesn't really have the ability to be lined with a material unless it were less that 25mm thick. Penn
  39. D

    Noise: What Is It? Exploring Sources & Types

    Can someone please explain to me or preferibly point me torwards a resource that will explain what is ment by noise? I know that it s some kind of unwanted disturbance in a signal and that we want to get rid of it, but where does it come from. when i search online about this i find a myrid of...
  40. P

    Noise Removal in Radio Telescope Observations

    while dealing with radio telescopes how can we remove the noise and other disturbances like microwave radiation etc.
  41. S

    The source of noise in amplifier

    hi for every one I am a new member in tis site. I hope from u to help my I have a hmoework so I want some help The question is What is the source of noise in amplifier & how can treat the noise? Thank u
  42. D

    Laptop performance and noise problems

    Just a couple of weeks ago, my laptop started making a very loud roaring noise and experienced a severe slowdown in performance (programs and windows open very slowly) at the same time. It takes a couple minutes after booting up for the noise to begin, but once it starts it is continuous. At...
  43. N

    Pitch vs Noise: Understanding the Difference and Its Scientific Explanation

    Hello everyone. I'm not a Physics major: I'm a Music major. And I have a question. I've read various books on acoustics, but I still haven't found the answer. Ok. The way I see it, there are 2 basic types of sounds (I didn't get this out of a book, it's my own conclusion from everyday...
  44. N

    Question about Noise vs. Music

    Hello everyone. I'm not a Physics major: I'm a Music major. And I have a question. I've read various books on acoustics, but I still haven't found the answer. Ok. The way I see it, there are 2 basic types of sounds (I didn't get this out of a book, it's my own conclusion from everyday...
  45. N

    Calculating Closed Loop Gain in a Noisy System

    Hi, Is it possible to calculate the gain of a closed loop system with Noise? Here's a diagram describing what i mean: http://img206.imageshack.us/img206/8955/cltfmh8.png I've got the following so far: Vout = \frac{A1A2Vin}{1 + A1A2B} + \frac{AVn}{1 + A1A2B} But the question is...
  46. E

    Improve SNR for Raman Spectroscopy with Photoresistor: Tips and Tricks"

    Homework Statement We are using Raman spectroscopy to detect the presence of chemicals from emitted light. We have a light transistor that behaves as a photo-resistor of 50k-ohm resistance. The light signal generates 2 microvolts of 2 kHz signal at normal Raman levels. We want at least...
  47. D

    Noise (electronic Engineering)

    Hey friends, Can you help me with the questions posted below ? a) How can noise affect an electronic system and the consequence of each ? (3 points) b) Noise is difficult to measure and characterize. State the reasons. (5 points) c) How do the choices of frequency and wavelength affect...
  48. R

    Understanding Noise Specification Units in Accelerometers and Gyros

    hello, I am stuck at understanding the units of noise specification of accelerometers and gyros. I am referring to the datasheet of 3DM-GX1 which has accelerometers and gyro sensors. the pdf is .. http://www.microstrain.com/pdf/3DM-GX1%20Detailed%20Specs%20-%20Rev%201%20-%20070723.pdf...
  49. 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.
  50. 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...
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