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. E

    Troubleshooting Static Noise in Speaker System with DC Adapter - Need Help!"

    Hello all. I'm not a regular from the forum or nothing, I've been looking for a solution for a problem with static noise in a speaker system and got to this post in the forum https://www.physicsforums.com/showthread.php?t=201439 is not what i was looking for but from what i read someone...
  2. W

    Could you me to deal with noise due to a electric motor?

    I am using an electric motor to impose displacements on a specimen, but when the motor is on, there is too much noise in the displacement and force signal. Everything seems to be nice when the motor is off. The frequencies of the noise are less than 10Hz, too low to be filtered. In...
  3. W

    Signal to Noise Ratio: Questions for my multimedia and signals class

    Question one Homework Statement x[n] = 5sin(0.22*pi) The root mean square (RMS) value eof a sin wave is known to be A/root(2) where A is the amplitude. If the noise in a system is known to have an RMS value of 0.5, what si the signal to noise ration (in dB) of the x[n] in this syetem...
  4. F

    MATLAB Adding noise to a Square wave in Matlab

    Hi, I've got a square wave: x = square(2*pi*10*t); with time vector: t=0:0.001:2; I've also got a random noise signal: r=randn(1,10000); I want to add the noise signal to the square wave, but I can't add them because they aren't of the same dimensions. I know I can use awgn(x,snr) but I...
  5. J

    Mystery of the Microwave Fan Noise Solved?

    First I thought of posting this on the random thoughts thread, but I need an answer to this bugging question. Why the hell a microwave (the cooking device) makes that fanlike noise? While an infrared device (electric heater), visible light device (a flashlight), x-ray machine do not make any...
  6. T

    Resistor Nyquist-Johnson noise formula question

    Hi all -- I had a question about the Nyquist-Johnson noise formula: \[ E_{\nu}^{2}d\nu=\frac{4R_{\nu}hd\nu}{e^{h\nu/kT}-1}\] which of course can be approximated for most purposes as $ E_{\nu}^{2}d\nu=4R_{\nu}kTd\nu$. I'm just wondering why the formula has $ exp(h\nu/kT)-1$ in the...
  7. 0

    Questions on Noise Budgeting for Electronics

    A few questions about noise. I am doing a noise budget and I am not sure if everything is correct... 1/f flicker noise Resistors show this noise. Horowitz specifies microvolt per decade frequency per applied volt. This would give me a false reading on a four point measurement, at least...
  8. L

    What happens to gaussian white noise when derived in continuous time?

    Hello, I've got a problem where a recording signal is a signal + gaussian white noise (quite classic). I derive this signal and while I know the theoretical result of the derivative of the noiseless signal, but I can't figure out what happens to the noise after the operation. So...
  9. M

    Radio Noise from the Milky Way

    First of all, new to the forums, so HELLO! I am currently working on a project and cannot catch a break on what I need to be looking for. The project consists of calibrating antennas based on the radio noise from the Milky Way. We would like to point the antenna at the center of the milky way...
  10. zoobyshoe

    Freud, Jung, and the Noise from the Bookcase

    I read an account of this incident years ago and have often wondered about it. Here's the short version: http://soultherapynow.com/articles/carl-jung.html A longer version is available at this separate source (which does not allow for copy and paste)...
  11. G

    Acoustic test for the sloshing noise in a tank

    I am currently doing an acoustic experiment, testing the sloshing noise made by the fluid content in a tank. My software and microphone gives me all the outputs from the sloshing noise but not the loudness calculation. I am needing a figure for every test to key into my statistical software and...
  12. H

    Noise Path Analysis for Four-Wheel Drive Vehicle

    The figure1 shows a for the configuration of a four wheel drive vehicle. The body is mounted on a chassis frame through a series of body mounts. The engine and transmission mounting points are also shown. The engine has two front mounts and a single gearbox mount to a body cross member...
  13. A

    What Happens to Electric Circuits When Exposed to Noise?

    I'm trying to find how simple electric circuits behave when the input is a random signal or noise. I'm wondering if anyone is familiar with this area or know of any resources they can point me to. Thanks in advance,
  14. S

    Sources of noise in geostationary satellite attitude determination simulation

    I am doing satellite attitude determination simulation using sun Earth sensors and Gyro modelling .I am using extended kalman filtering for attitude determination. the sequence of operations I am doing are % Simulation data % Spacecraft data % Gyro data % Sensor data. % Control system...
  15. S

    Accelerometer Noise PSD to Velocity Random Walk

    I have the intrinsic noise PSD spec for Honeywell's QA3000 accels, and I need to find the velocity random walk due to noise to show that I'm within my allowable. The PSD is given in units of g^2/Hz vs Hz. I'm given a velocity random walk due to noise spec of 15 (micro-m/s)/rt(s) that I must be...
  16. M

    Mathematica Plotting White Noise Distribution in Mathematica

    Does anyone know how to plot noise in mathematica? I want to plot a normal distribution which is white noise in the time domain. This is because I want a constant power spectral density but Gaussian spread of values. Anyway I can plot a list of normal distributed numbers but want to know how to...
  17. N

    Noise measurement-decrease in sound intensity with distance

    I am making a noise level meter, that would trigger an alarm, if the noise level has reached hazardous levels. However, one problem with noise is that it'd intensity decreases with distance, so that the meter would percieve a low sound near the meter and a high sound far away as equal. So does...
  18. M

    Mathematica Modelling noise in Mathematica

    Given a power spectral density Sn(f) (or alternatively the autocorrelation function), is there a way to output random noise in Mathematica? Not sure if anyone here will know this but it's worth a try.
  19. S

    How does noise impact the potential measured in a circuit?

    Hello, I am trying to understand how noise affects the potential measured across a certain point of a circuit. If we have two alternating voltage sources in a circuit, I understand that the "sum" of the potentials provided can affect the potential at the point of interest. However, I am...
  20. W

    Too much noise in Embedded system?

    Too much noise in "Embedded" system? Hey everyone. I'm working on putting a circuit board (with microprocessor, eventually) into a car for electro-pneumatic shifting on a manual transmission. This means that the circuit has to run on a 12V source being charged by an alternator. I have a...
  21. R

    How does the noise power in a conductor depend on its length and resistance?

    The noise power in a conductor is given by P = k.t.B Does this mean the noise power is independant of the conductor length? Also, does this only apply for a conductor with no resistance? Thnks, Rudi
  22. T

    Can light produce darkness and can noise procude quiteness 4

    This is do with wave I think but I'm intrigued with this. As with waves sometimes they can cancel each other out but what about this: Can light produce darkness? Can noise produce quietness?
  23. T

    Are Active Noise Control Stereo Possible?

    Is it possible to create an active noise control stereo that works like the headphones except they are stereos used to silence noise in a a room?
  24. T

    How can I create an active noise control stereo using simple terms?

    I want to create an active noise stereo which works like the headphones except it's a big speaker. I need your help on how i would go about doing this? I ain't no electrical engineer or anything, in fact I have no knowledge whatsoever so try to help me using simple terms.
  25. T

    Introductory acoustics & noise control tutorial

    Homework Statement A small reverberation chamber is constructed with concrete walls. Its internal dimensions are 2 x 2.5 x 3m. Calculate the final steady-state sound pressure level produced by a source of 7.5microwatts acoustic output. Assume the absorption coefficient of the concrete to be...
  26. X

    White noise vs Black body radiation

    Hi all: I am confused about one question. When we detect signal from human brain using coil in Nuclear Magnetic Resonance, two source contribute noise to our signal. One is coil itself. The other is human brain. Why can we think the noise from human brain is white noise? Can we compare the...
  27. S

    Signal to noise ratio/CCD saturation problem

    Homework Statement A 4m telescope has a 16bit controllr with a gain of 1 and must detect faint stars(M>15) without saturating the bright stars(M=8-10). (i) What is the max no of photo-electrons that can be registered before saturating the CCD? (ii) The zero point of the system is...
  28. A

    Capacitive Current: Calculating Noise Across Capacitors

    Hi, Suppose you have a simple capacitor, where the potential on one side is held constant and the other is allowed to vary randomly. What is the capacitive current? thanks,
  29. L

    EMC noise in instrumentation amplifier.

    Hello, First thread on this forum! Thank you for giving me you're opinion about a question that I have. I am using a data acquisition system (ADInstruments Powerlab 16/30) to record muscular activity from electrodes. So far, everything is working properly. I recently got an approval to...
  30. T

    Noise Power Paradox: Explaining Limitations

    Homework Statement Explain why the noise power across a resistor in thermal equilibrium is limited in contradiction to the formula for the noise V_{RMS} = \sqrt{4RkT\Delta f} which states that if we measure with infinite bandwidth we have infinitely large power Homework Equations...
  31. F

    MATLAB Matlab - creating Gaussian noise

    Does anyone know how to create a matrix of complex Gaussian noise (with unit power = 1 and mean of zero)? I need to define a test sample for my algorithm, but I'm stuck at defining my test bench. Any help would be appreciated, thanks!
  32. Andre

    Photography drizzle, roses and noise

    This is what happens to roses after a night in the drizzle. I'm sure, Drizzle, that you'll think of a witty reaxion. :biggrin: Unfortunately, the day was still dull, so I had to tweak contrast to get some dynamics back in the exposure. and sure enough, -you know me- getting in...
  33. M

    Filter noise by using average method

    Lease help me, I have an assignment that ask me Filter the nois of this function f(x)=cos(0.1t) + noise the noise is random number between -0.5< n < 0.5 Filter the noise out using the average noise method? ( in excel ) Thanks
  34. K

    Converting noise into electrical energy

    Hello everyone! I have an idea of making a device that can convert noise into electrical energy. In many fields (industries, cars, construction machines,...), some used machines make much noise, then I thought as sound (noise) causes mechanical energy, why not convert that mechanical into...
  35. N

    Noise Troubles With BNC Connectors: Investigating Causes & Solutions

    Hi! I guess this thread (could) bear similarities to the discussion in the "Low noise low pass" https://www.physicsforums.com/showthread.php?t=332819" thread, but I didn't want to hijack that :) so beginning a fresh one. I find that the electronic noise gets aggravated, when I connect the...
  36. 0

    Low Pass Filters: Is Noise an Issue?

    Is a low pass with an inductance less noisy than one with a resistor due to thermal noise? Will an RC low pass between two op amps necessarily be less noisy when the C is large and the R is small? Does this matter in real life circuits?
  37. A

    Delta-Correlated Gaussian Noise

    Hi What is \delta-correlated Gaussian noise? secondly, how is it that its correlation function is given to be 2\sigma^2\delta(t)? Thanks
  38. F

    Johnson noise power distribution?

    I've been reading through the Feynman lectures (almost done with Volume 1), and I have been trying to prove everything to myself. I have a bit of a problem now though, in Chapter 41 on Brownian motion, Feynman shows what the voltage in an LRC circuit is due to thermal noise, and then says that...
  39. M

    Improve SNR Microphone Amplifier: Opamp Tips

    What are some ways to improve signal to noise ratio for a microphone amplifier, beyond getting low noise components. My amplifier is a single opamp.
  40. G

    Eliminating noise from Excel Data

    I am observing the Sun with a small radio telescope for a research project. I am measuring the intensity of the flux and comparing it to X-ray flux data from the NOAA. I am plotting radio flux intensity against time and i get a big "hump" in the middle of the day due to less atmospheric...
  41. H

    Is the Universe's Electromagnetic Radiation Noise Uniformly Distributed?

    Hi, Does the cosmic electromagnetic emitters, if viewed in the function of electromagnetic intensity and in the particular wave length, follow the gaussian characteristics or is the noise uniformly distributed over all wavelengths? I.e. is there "tranquility" in intensity (or least amount of...
  42. L

    My laptops fan is making a loud noise?

    does anyone know how i can fix this? it's really annoying and i don't want to have to bring it in seeing as it sounds like the big external fan
  43. M

    Low noise 60 Hz notch filter circuit

    Does anyone have a very low noise 60 Hz notch filter circuit that will not attenuate over 100 or a low noise bandpass from 100 to 20000 hz .
  44. R

    Data collection - noisy signal - how much noise is acceptable?

    I'm collecting voltage data, and I need a resolution of at least .05mV, which I think I can provide over the range of voltages with my inexpensive A/D board. The problem is, the signal fluctuates maybe 1mV up and down, and so I get a noisy signal. I've tried running a low-pass filter through it...
  45. K

    Measuring voltage across piezo speaker, getting resonating noise.

    Hi. I'm trying to measure the milliseconds of duration of output from a little piezo speaker that is on a circuit (a freezer control unit). I tried connecting an oscilloscope across its leads, but when I apply power, I hear this resonating noise which does not sound healthy. This is only when...
  46. 0

    How Can I Improve Signal Transmission and Reduce Noise in High Magnetic Fields?

    I have a very small signal coming from a thermocouple \mu V \mathrm{to}\, nV range, which gets drowned in noise when I transmit it via a 2m BNC cable, even the lock in runs into problems. I am about to amplify it at the source, and while I am at it, I will try to do a few more tricks...
  47. Topher925

    How to remove 60Hz noise from square wave?

    I have an amplification circuit where I am essentially reading a somewhat deformed square wave and I am having a lot of trouble with 60Hz noise from the walls being superimposed on my signal. The signal of interest goes from 5v - 0v, has a period of about 60ms, and I need it to be relatively...
  48. L

    Noise charateristics in sensors

    Is noise in sensors always gaussian? I was playing with acceleromter data in matlab. I decomposed the data into high frequency and low frequency. The high frequency noise distribution looks like a gaussian. Is this common to sensors?
  49. C

    Calculate Ambient Noise Intensity Increase: 86.0 dB - 85 dB

    A machinist is in an environment where the ambient sound level is of 85 dB, i.e., corresponding to the 8 Hours/day noise level. The machinist likes to listen to music, and plays a Boom Box at an average level of 86.0 dB. A.Calculate the INCREASE in the sound level from the ambient work...
  50. V

    Varnish or Potting, Which one is Better to Avoid Humming Noise from Inductor

    Someone just tell me that, "varnishing an inductor can reduce humming noise much better than encupsulating it", and this is what his friend told him where his friend worked in power supply field for over 10years. (But I don't know did his "encupsulating" means potting) Or did he mean varnish...
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