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. A

    Noise generated from turbulent shear flow

    Hi guys, its been awhile since i have been back. Right now, i am involved in some research on aeroacoustics and i have been trying to get some of the basic fundamentals on aerodynamic generation of sounds. Unfortunately most of the online literature do not give much details on the physics of...
  2. A

    Polar bear family's noise seal feast

    This unique 6-minute video shows a she-bear and her two cubs devouring a seal, while mummy bear is growling for miles around to be heard, to warn off others from getting too close. http://www.dagbladet.no/2011/09/07/nyheter/innenriks/isbjorn/dyrenes_nyheter/17989869/
  3. J

    Cancelling out Power Supply Noise out COMPLETELY

    Hi I have a HV (R2) resistor that I want to test for noise. Assuming the 2 low voltage resistors are perfectly stable and HV R1 is also perfectly stable. How could I completely cancel out the noise of the power supply if the bridge was slightly unbalanced? Does any circuit exist that can do this?
  4. F

    Digital vs Analog - Noise Distortion

    In my textbook it says this: "Digital communication, which can withstand channel noise and distortion much better than analog as long as the noise and the distortion are within limits, is more rugged than analog communication. With analog messages, on the other hand, any distortion or noise, no...
  5. T

    What is electrostatic noise and how does it affect analog and digital signals?

    I started an electrical engineering degree this semester. My book says that electrostatic noise meaningfully affects analog but not digital. But it does not say what electrostatic noise is, and neither Google nor Wikipedia readily yield an answer to this question: What is electrostatic noise?
  6. J

    Can Air Compressor Noise be Cancelled Without Affecting Air Flow?

    Is it possible to cancel noise from an air compressor while still allowing air flow to keep it cool?
  7. C

    Why is directional noise correlated noise?

    Hi everyone, This is not a homework question but I question I have from reading a signals processing paper on acoustics. Suppose there is a sound source in a room S(t) and two microphones X_1(t) and X_2(t). Then the standard acoustic propagation model has that X_1(t) =...
  8. D

    Measuring Co-Channel Interference: How Can It Be Done?

    Dear all, I am trying to understand something for SNR, I know that is the ratio of the Power of a signal divided by the Power of noise. According to wikipedia Signal-to-noise ratio is defined as the power ratio between a signal (meaningful information) and the background noise...
  9. Z

    Comparing Best-fits of different data sets that have different noise levels

    Suppose I have 2 sets of data: day1 and day2. I want to fit a model to both data sets and then compare them to each other to see which one fits the model the best (the fit is done with a computer using non-linear least squares method). The RMS of the fit would be fine except that day1 has much...
  10. N

    Find Signal to noise ratio (SNR)

    has a transfer characteristic |H(f) given in the link below. The transmission is at maximum error-free rate of 4,800 bps. Compute the SNR (signal-to-noise-ratio) at the channel output. Does the output signal suffer from any distortion? http://imageshack.us/photo/my-images/263/79465468.jpg/...
  11. D

    How can I determine noise levels in orifice flow meters?

    My employer has asked me to derive a method or equation for determining noise (in decibels) in orifice flow meters. I was wondering if anyone has any suggestions that could help me get on my way? I've been looking at basic principles of aerodynamic and hydrodynamic noise predicitions. As far as...
  12. K

    Effective Noise Power Spectral Density

    How to calculate the effective noise power spectral density, when a noise factor of 3 if given and if said to make any assumptions. We know Effective Noise Temperature N = k.Te.B I'm assuming it as Te = 290 K x (10 NF/10 - 1) and what about 'B'?
  13. K

    Noise Power Calculations in dB or dBm

    The ourput Noise Power is given as No = kTsBG + kTeBG ...= k.(Ts+Te).B.G But when it is asked in dB or dBm, How to calculate it something like 10Log10(Value) or 20Log10(Value)
  14. T

    Hovercraft vibration noise problem

    I have built a 3' by 4' hovercraft (with rounded corners) out of plywood with a pond liner bag skirt. it it powered by either 2 battery operated leaf blowers or 1 plug in electric leaf blower. I have encountered a problem with both power sources. The hovercraft makes a loud vibrating noise...
  15. J

    How can I reduce noise amplification in my Faraday Cage?

    Hi everyone, I have recently built a Faraday Cage. However it seems to be working in reverse and amplifying the noise! My test setup: I place a 3.3 Mohm Bulk metal precision resistor across the terminals of the meter and measure the pk-to-pk noise using the meter. I now place the meter...
  16. P

    Experiment: Ridding of pulse generator noise

    My research involves using a detector that I am trying to test with a pre-experimental setup. To test the functionality of the detector, I am pulsing a light source near the detector using a Picosecond Pulse Labs pulse generator. Here is where my troubles/question comes in: the pulser is...
  17. S

    Noise suppressor improves reception, why?

    Newbie here, not an EE, just an old Air Force electronic tech from the 70's...please be gentle. :) I recently installed a noise suppressor inline to the 12v on my 70 Lincoln AM/FM radio. It cleaned up the "whining" noise just fine - but one interesting side note is that my FM stations come...
  18. N

    Confused about Power Spectral Density (and relation with rms noise voltage)

    Hello, In the chapter on thermal noise it says that the spectral distribution per Ohm of resistance is a certain shape (constant till a certain f and then ~ 1/f²). What is this expression? Is it physically the power dissipitating in the resistor, at least a certain part of it...
  19. D

    Removing Noise from sound Audio Recordings

    Is there any specific theory that states how we can remove noise from audio out put. I am a developer. I know no basics in terms physics about Audio, Noise . I record audio using an application in iPhone. I get lot of surrounding noise. I wanted to remove those noises. Is there any algorithm...
  20. P

    Is there significant noise in the neutral wire with a sense resistor connected?

    I have a sense resistor connected in series with the neutral wire. From the oscilloscope i detect noise of around 500mV - 1V across the sense resistor at high frequencies 60khz- 100khz. I see the noise once the power plug is inserted to the socket, although not switched on(live wire not...
  21. Kawakaze

    Noise from unplugged power supply :S

    I have a ccd camera that I put a peltier element into, and there is noise from the power supply, even when it isn't plugged in. Just plugging the jack in gives noise, I tried the bypassing thing with a capacitor with no effect. Plugging the PSU in gives no change. I tried moving the power supply...
  22. Y

    Hypothesis testing for multivariate processes(ljung box white noise test)

    hi guys, I'm trying to understand how the critical value of Q-statistics is calculated in multivariate ljung-box test. or even more simply, in the univariate ljung-box test. initially i used MATLAB for hypothesis testing, MATLAB as an output furnishes the critical values, but the modules in...
  23. T

    Medical Analyzing Neighborly Noise Differences

    analyze please? Our neighbor has a noisy dog and a Sportster. Niether is louder than the other or actually very loud at all. I don't mind the bike but the dog really gets me upset because there is a history of her and the dog being much worse and I've had to call the police. I like...
  24. M

    What is the Advantage of Using a Gaussian Distribution of Noise in a System?

    what is the advantage of using a gaussian distribution of noise (white/colored) in a system over any other distribution ??
  25. M

    Johnson and Shot noise the Frequency Term

    I am a bit confused over the frequency term that appears in Johnson and Shot noise formulae. What is this term? Is it bandwidth? Of what? In relation to say a photodiode, is it the range of frequencies being detected? And how would this relate to say a DC circuit which no frequency terms...
  26. B

    Noise Canceling Headphones Problem

    Hey, I figured you physics geniuses might have an idea regarding what's happening to my headphones: When under certain conditions (some of which I've nailed down, but others I can't figure out) the headphones will start making insanely loud "electric" noises that resemble the "zzzz" sound...
  27. U

    One sided noise spectral density VS double sided noise spectral density

    No is the one sided noise spectral density in communication systems. N is the double sided noise spectral density. The relationship between them is given by 2N = No but I don't understand why it is like that. Why isn't it N = 2No instead?!
  28. P

    Help ~ Calculate the maximum noise voltage

    Help!~ Calculate the maximum noise voltage Homework Statement Two conductors, each 10-cm long and space 1-cm apart, form a circuit. This circuit is located where there is a 10-gauss magnetic field at 60 Hz. What is the maximum noise voltage coupled into the circuit from the magnetic...
  29. T

    Data comparison and noise measurement

    Hi, I would like to measure the signal noise in a tv cable after introducing a splitter and compare it with the original signal. Keeping in mind the bandwidth frequency of the tv cable signal transmission, what kind of instrument do I need? Oscilloscope perhaps? At what speed? I don't know...
  30. N

    How can I reduce noise levels and promote respect in shared living spaces?

    I have a roommate who blasts his music and bass below me till 5 am every night. It makes it very difficult to sleep and I have asked him to turn it down many times and every time he just curses me out. I would like to make it so his speakers don't play as loud or even that the bass is softer...
  31. P

    Noise Shielding by Rear-Mounted Engines on Aircraft

    How is the noise sheilding provided by the fuselage when the engines are mounted at the rear end of the aircraft ? for example-SAX 40
  32. D

    Invert Battery and Maintaining Low Noise

    I am trying to invert the the output of a battery so I can run an op-amp double ended with 5 volts and -5 volts. The battery itself produces 7.5 volts so I am passing it through a linear regulator to drop it down to 5 volts with low noise, at the expense of heat/efficiency. This is all great...
  33. A

    High-frequency (inaudible by humans) acoustic noise from stepper motor

    Hello, I am using stepper motors for some neuroscience experiments on rats. The problem is that our experiments are being corrupted by high-frequency noise. The acoustic frequency of the noise is high enough that humans can't hear it, but rats can (humans can hear up to 20 kHz, whereas rats...
  34. Saladsamurai

    MATLAB How Can I Filter Out Noise in Combustion Pressure Data Using MATLAB?

    Hello all :smile: I am currently doing some experiments in combustion where the pressure inside of a closed vessel is recorded while a mixture of fuel/air are ignited. It's obvious from a physical standpoint that the plot of the recorded pressure data against time should resemble a...
  35. L

    How do I measure the Noise Figure in an Antenna System

    I have an Antenna system using two patch antennas, and I'm trying to determine the SNRin and SNRout of the system. I'm trying to determine the noise figure - is there a way to do it using scattering parameters? Thanks!
  36. R

    Doubt regarding Noise in the system

    Hi, I am new to circuit design. Although, I am designing CSA&SA(charge sensitive @ shaping amplifier) for our detector system to detect the radon gas emission. We soldered every thing and we observe the output that is bit noisy. I learned some concepts in my course about...
  37. D

    Signal-Noise Ratio: Decibels & Resolving Signals

    I am trying to get an understanding of what a good signal to noise ratio in terms of decibels. My SNR is roughly 20 dB, and am concerned about being able to resolve the signal from this.
  38. M

    Johnson and Shot Noise at 20*C with 9V Battery and 100Kohm Resistor

    A battery of emf 9V, and negligible internal resistance, has a 100Kohm resistor connected across its terminals. What are the values of johnson and shot noise at a temperature of 20*C if the measurement bandwidth is 10KHz? At what temperature would the johnson and shot noise contributions to...
  39. K

    What Are the Noise Parameters of a Very-Low-Noise Amplifier?

    We need a very-low-noise amplifier for a special application, and we buy such an amplifier with a noise bandwidth of 2.4 MHz and an amplification of 1000. To test it, we take a set of "perfectly" shielded standard resistors, connect each if these to the amplifier input, and measure the rms...
  40. N

    Is Autocorrelation of White Noise Zero?

    I am really new to this and so I am trying to understand some basic stuff here. Autocorrelation of a univariate white noise is 0. Am I correct?
  41. S

    How to calculate signal and noise power

    hello, i have a signal current I(t)=Acos(wt+theta) How can i calculate the signal power and noise power individually? thanks Reza
  42. L

    Noise Nuisance: How to Make Your Neighbors Behave

    I keep having to call the police on my neighbors for them playing their bass music too loud. Will these sub-humans eventually get a ticket, or will the cops just keep showing up and saying the same thing over and over again to them? I had to call twice yesterday and just called again this...
  43. G

    Logic Design- Transfer Characteristics and Noise Margin

    Hello, I have the following question which I'm not quite sure about. I have the following Transfer Characteristic for a buffer. You can see the graph breaks at the points (2,0),(3.5,4),(5,5) http://img521.imageshack.us/img521/5052/captureen.jpg I need to set the appropriate values...
  44. A

    Noise in Circuits: Causes & Solutions

    I wonder if anyone could tell me how and why the noise is created by the any electronic circuit or clipping circuit? thanks
  45. A

    Acoustic Parameters for Passive Noise Control

    1. Homework Statement Actually I am doing a research project about Noise Isolation. I took my college cafeteria as an example and I was provided with a Noise Simulation software( Soundplan). There I can work mainly with the SPL and the absortion coefficients. I found another software ( EASE)...
  46. B

    Find Eb/No : signal to noise ratio

    Homework Statement If the received signal level for a particular digital system is -151dBw and the receiver system effective noise temperatyre is 1500K, what is E_b/N_o for a link transmitting 2400bps? solution says: (Eb/N0) = –151 dBW – 10 log 2400 – 10 log 1500 + 228.6 dBW = 12 dBW My...
  47. S

    How Does Oversampling Affect SNR in Analog Signals?

    Sampling theorem says that we should sample at least at a double rate than the bandwidth of the signal : Fs>=2B. Ideally Fs==2B e.i. oversampling is unnecessary. However, there's always noise present in the signal. Hartley's theorem connects the SNR with the bandwidth and the sampling rate for...
  48. L

    Mathematical model for reducing mri noise

    dears I study nuclear engineering (medical radiation ,MS) , my proposal for graduation is (Modeling of Acoustical Noise in MRI and It Is Validation Through Measurements). I want to make and deliver a mathematical model for reducing noise in mri,would you please tell me what should i do? and...
  49. F

    How Can Active Spatial Noise Control Reduce HVAC Noise in Meeting Rooms?

    Hello everyone, I'm new to this forum, and though this question may be addressed already in another thread somewhere, I'm hoping to get some focused discussion about solutions going here. Problem: HVAC noise is propagating down the HVAC duct, entering a meeting room / boardroom. The...
  50. M

    How can I determine the frequency of excessive noise in a fireboat cabin?

    I am responsible for investigating excessive noise problems in the cabin of an aluminum fireboat. I have no idea if the problems are with structure borne noise or airborne noise, so here is what I was thinking about doing, please let me know if there are any problems with this method. I was...
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