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. arcTomato

    The power spectrum of Poisson noise

    Dear all. I have made the power spectrum of Poisson noise(expected value ##λ=2##), and it becomes like this I think this is not good. I don't know why the power is so high when Random variable(x axis) is 0. I tried another expected value version ,but the result didn't change. so I would like to...
  2. E

    Engineering Input-referred thermal noise voltage (Razavi exercise)

    So this is a problem from the legendary Razavi book "Design of Analog CMOS Integrated Circuits" (Specifically, it is the problem 7.7 (c)). I got the solutions online but when I try to calculate the noise expression myself, I don't arrive at the same result. Lambda is assumed zero for neglecting...
  3. H

    Unit of Velocity from a Random Walk measured by an accelerometer

    Hi, I am working on a kalman filter where my measurement equation involves "-g + v" , where g is in m/s^2 and v is velocity random walk given in m/s/sqrt(hr). Feels like a stupid question, but how can I transform the unit of velocity random walk so I can do the calculation correctly?
  4. berkeman

    Improving hearing "Signal to Noise" by turning your head

    I have long found myself turning my head fairly quickly when a noise steps on something I'm trying to hear. Sometimes it is just a noise like a bang or a pop that steps on a conversation I'm listening to, and sometimes it will happen when another person starts to speak and interferes with a...
  5. M

    Does water flowing through a pipe make noise?

    I've my small incursion team entering a 10 foot diameter water outlet pipe using electric sleds for propulsion and was wondering about sensors in the pipe detecting them. They're wearing suits that mask their IR, but what about noise? The pipe flow is 3.18086e+07 l/h with a 1.25 m/s current...
  6. CPW

    Misc. Getting used to new house, but what's best for noise elimination?

    So, my wife and I really like our new house, but after living in it for two months we desire to find a smart way to deaden the noise. You see, our previous house was smaller, had carpet mostly, and did not reflect the noise inside near as much as this new house. Our new house is larger, has...
  7. F

    Poisson distribution and Shot Noise

    My setup: I have the an LED (LED370E) in front of a photodiode (S12915-16R). The photodiode is connected to an ADC (DT5751) which has a counting functionality. The way it works is that it counts how many times the signal goes above a certain threshold and makes a histogram out of it. I know...
  8. O

    I Higher-Order Time Correlation Functions of White Noise?

    Suppose I have Gaussian white noise, with the usual dirac-delta autocorrelation function, <F1(t1)F2(t2)> = s2*d(t1-t2)*D12 Where s is the standard deviation of the Gaussian, little d is the delta function, and big D is the kronecker delta. For concreteness and to keep track of units, say F...
  9. Plat

    Turbo pump - vibration and noise at a certain RPM

    I have picked up a used pfeiffer turbomolecular pump and controller for pretty cheap. It runs like a champ, completely smooth and quiet except for when it’s first starting up. As it approaches 5500 rpm, it starts vibrating somewhat and sometimes produces a momentary scraping noise when the...
  10. L

    High pitched noise with some elctronics

    Hello:) I am working on my new 3d printer and i came across an interesting situation. According to the manufacture, my stepper motors need to have a voltage of roughly 0.95 volts. I checked mine and they were 0.81 volts, hence the not so smooth prints. Ok, so i increased the voltage to the...
  11. fluidistic

    Understanding 1/f Noise in DC Voltmeters: Causes and Solutions

    I've been told that the 1/f noise for DC voltmeters is a problem when they measure a very low voltage (i.e. around 1 nV). Some readings can take weeks or even months. However, a DC voltmeter would have no problem to return a stable reading of a simple resistive circuit, of the order of the volt...
  12. iVenky

    Power of noise after passing through a system h(t)

    **Reposting this again, as I was asked to post this on a homework forum** 1. Homework Statement Hi, I am trying to solve this math equation (that I found on a paper) on finding the variance of a noise after passing through an LTI system whose impulse response is h(t) X(t) is the input noise...
  13. iVenky

    I White noise & 1/f noise after a system h(t)

    Hi, I am trying to solve this math equation on finding the variance of a noise after passing through a system whose impulse response is h(t) X is the input noise of the system and Y is the output noise after system h(t) if let's say variance of noise Y is σy2=∫∫Rxx(u,v)h(u)h(v)dudv where...
  14. Muhammad Usman

    Understanding Capacitor Behavior for Noise Filtering?

    --> Hi, I am reading about the capacitors. I have read that the capacitors block DC and behaves as open circuit in DC while short circuit in AC. The reason behind this is the charging and discharging of the capacitor. What is my perception about it, I will mention about it. " During the DC...
  15. Isa

    I Question about noise in entanglement experiments

    Hi everyone While learning about quantum mechanics, I became curious about the real-life experimental data. Wikipedia says that entanglement experiments require coincidence counters, because the majority of the signal received by detectors is noise. It further says, that coincidence counters...
  16. DarkMattrHole

    Low noise AC-DC, DC-DC switchers for mixed signal analog I/O?

    Hi all. So is anyone having any luck with sw. power PCB mount supply modules for mixed signal? I have been experimenting with little DC-DC +5, +-15 and the TDK-Lambda AC/+5/+-15 power module. I have a mixed signal design that has a small size and low weight factor in my design. I have about...
  17. N

    Reducing Noise of Linear Actuator up to 125kg Force

    Hi, For a machine I am designing, the linear actuator would ideally not produce much noise as it is intended to be in a relatively quiet environment. Just wondering do all actuators produce a large amount of noise pollution (it would need to produce a force of up to 125kg so it is not a small...
  18. iVenky

    I Why high Q factors have low phase noise

    If we define Q factor as 2*pi* energy stored/ energy dissipated per cycle, what's the physical insight behind obtaining low phase noise for oscillators when we have high Q factors? (I know the mathematical derivation based on finding the frequency profile of an oscillator (like LC oscillator)...
  19. O

    Johnson-Nyquist noise of an inductor

    Homework Statement Although it's easy to find calculations of thermal noise for resistors and capacitors, the equivalent for inductors is not found. What is the relevant formula? Is there some simple conversion for this? Homework EquationsThe Attempt at a Solution
  20. C

    How does the phase noise of the LO effect IF accuracy?

    Hi, I have a roughly 1.1 GHz signal to be downconverted to 100 MHz by mixing it with a 1 GHz local oscillator. I am not sure how to choose the performance of the LO. In particular: let's assume the LO has a jitter of 100 fs rms. At 1 GHz this corresponds to a frequency error of 100 kHz. Does...
  21. Mzzed

    Connect isolated ground to Earth?

    I am currently working on a high power class E amplifier which will sit inside a metal enclosure. It is powered by two power supplies - both are isolated but one of the power supplies is mounted in the same enclosure. The power supply itself is in a metal case and that case is connected to...
  22. chakr

    USB Hub Noise Filter: Reduce 500mV Amplitude & 10MHz Frequency

    Hi, I designed a small wireless sensor that can run from 5V USB power. I use a USB hub to power my device via a USB cable. There is so much noise on the 5V USB line that my device readings turn inaccurate. Using the oscilloscope I can see noise frequencies of 10MHz and down to 100kHz, assuming...
  23. otaKu

    Confused about the Signal to Noise Ratio

    Hello everyone! It seems to me that there are many ways of calculating SNR depending on the type of signal and the nature of problems. I was able to get a decent amount of information for electrical signals but couldn't find resources which discuss the topic in a more generalized manner. I was...
  24. Theerapat

    PD pump (Rotary lobe pump) -- loud noise

    Hello, I have a problem with the rotary lobe pump, it causes a very loud noise when running. The pump specs are as follows: Liquid: Syrup (The liquid is in the 15,000 liters tank.) Viscosity: 2200 cPs Temp: Ambient Flowrate: 15 m3/hr Discharge pressure: less than 2 bar (open ended pipe) Inlet...
  25. R

    I Smoothing Numerical Differentiation Noise

    I am using the "knife-edge" technique to find the intensity profile of a rectangular laser beam. The data that is obtained using this method is power, the integral of intensity. Therefore, to get the intensity profile we must differentiate the data. So, as expected, my data looks like a ramp...
  26. P

    Stargazing How is noise removed in radio telescopes?

    For an optical telescope, light pollution is a problem and that's why put ground-based telescopes in remote places where there isn't much light. However, aren't we bombarded by radio waves from satellites for our phones and TVs? How do radio telescopes remove those?
  27. MatthijsRog

    I Fitting a curve over noisy data

    Hi all, I performed a resonance experiment over the past two weeks, in which I collected the intensity of a Fabry-Perot cavity whilst adjusting the mirror distance with a piezo-element (the specific setup of the experiment is fairly detached from the question I will ask). My raw data is...
  28. F

    Acoustics (Environmental Noise): LAFmax vs Shot Noise Level?

    Hello, new poster, I am trying to do a fairly simple, but non-standard, environmental noise model run for a shooting range. The standard against which noise from the shooting range is to be compared is the Shot Noise Level (SNL). SNL is defined as the logarithmic average of the 25 highest...
  29. J

    Problems snubbing HF noise on flyback transistor

    Hello, I am working on the design of a flyback converter based on the LT3751 capacitor charging circuit. My design is similar to the 42 A cap charger example on pg. 25 of the LT3751 datasheet. In my case, the circuit runs on 12V and steps up the output to 430 V, but I am having some major noise...
  30. D

    I Noise level at high-rise buildings

    What is the noise level at a high rise building if one was supposed to leave the window open in a balcony on the 80-th floor and above in an apartment on a skyscraper built in the city center of a large city like New York or Seoul, with all this car traffic underneath with their horns and sirens...
  31. T

    A Planck 2015 CMB temperature individual pixel variance

    Hi, I'm hoping someone can point me in the right direction please. I'm using the Planck 2015 CMB temperature (intensity) SMICA pipeline maps (Nside = 2048) and am trying to determine the temperature variance of each individual pixel. Variance and hit-count were provided with the 2013 CMB maps...
  32. C

    Can a loud inaudible sound drown out audible noise?

    To the best of my knowledge: a powerful oscillation at one frequency means more energy is required to make same medium oscillate at another frequency. Since sound perception works by detection of air oscillation, could a sufficiently powerful oscillation at an inaudible frequency (to humans)...
  33. C

    I Calculating signal to noise ratio for deimos data

    I'm currently working with the 1d DEEP2 DEIMOS fits files (see http://deep.ps.uci.edu/deep3/specprimer.html) and am trying to define some exclusion criteria in Python 2.7 for the data based on the noise. What's the best way to quantify the noise in order to do this? Thank you!
  34. M

    Studying Does white noise impair studying, reading or recall/memor?

    Hi, I recently have been trying to look into whether or not white noise works as a means to block out external sounds so i can concentrate. However, I want to know whether it actually impairs studying and reading. I do not care if it has no benefit, as long as it has no negative effects. I am...
  35. D

    Fundamental noise limit for an ideal photodetector

    Homework Statement As the title says, I'm trying to calculate the fundamental noise limit for an ideal photodetector, by specifically looking at the rate of incidence of annihilation of photons (and subsequent excitation of conducting electrons) on the detection surface. Since I'm looking for...
  36. CMW328i

    Noise Modelling - Digital communication systems

    Hi all, Teacher here looking for some guidance. I'm teaching a class that I took myself a few years back, and I'm looking at my solution to a problem but I have a random value in my answer (which I know to be correct) but I can't for the life of me remember where this value came from! Can anyone...
  37. D

    Automotive Troubleshooting Idle Flutter Noise in a Mini Cooper | Engine Noise Fix

    Hello guys, I am currently having an annoying issue with my Mini Cooper (1.5-liter 3-cylinder TwinPower Turbo). When I leave it idling, above all when the air conditioning on, I can spot a strong fluttering noise clearly audible from the tailpipe. It could be described as an impulsive noise...
  38. W

    Combining High and Low Pass Filters

    Homework Statement Suppose we have a noisy signal (superposition of many frequencies), but we are only concerned with a particular part of the signal within the noise at a frequency f(desired) = 1 GHz. In a sentence or two, explain how you could isolate the desired part of the signal by using...
  39. A

    Help reading Noise Characteristic graph for sub-nanovolt amp

    These are the links to the specific product I am looking at and its noise characteristic graph. http://www.emelectronics.co.uk/a20.html http://www.emelectronics.co.uk/graphs/a20graph.htm I understand the graph for the most part, but I am confused about which one of the four filters that are...
  40. N

    Cross-correlation of white noise process with its conjugate

    If w[n] are samples of the white gaussian noise process, I know that E[w[n1] w[n2]] = 0 for a WGN process. what would the following expression lead to: E[w[n1] w*[n2]] = ? Would it also be zero? Thanks a lot!
  41. entropy1

    B Does the Amplitude of White Noise Double When Two Samples are Added Together?

    Suppose you have two samples of white noise of equal amplitude. If you add them together ((sub)sample-by-(sub)sample that is), do you get one sample of white noise with twice the amplitude? How about pink noise?
  42. M

    Noise I'm getting in my summing amplifier

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > I am measuring EC of solution . I got Vec is 0.98V . After that, I took it to summing amplifier to reduce error from measurement . However, I saw a problem is that Vout of summing amplifier was...
  43. M

    Thermal Tumbler and unusual noise....

    Back in... man... probably 1996 I went to work with a thermal tumbler filled with some hot beverage or another. I settled in and took a swig; the liquid was good and hot and I kind of marveled at how well the tumbler worked and how it was nice to have a warm drink in my cool environment and...
  44. Auto-Didact

    A Penrose: Noise in LIGO signal implies CCC

    Roger Penrose, July 2017. Correlated "noise" in LIGO gravitational wave signals: an implication of Conformal Cyclic Cosmology
  45. auou

    A Uncovering the Truth Behind LIGO's Gravity Wave Detection: A Critical Analysis

    Hi, I was looking for a second opinion on this article regarding LIGO's gravity waves and if it made sense or not. https://www.forbes.com/sites/startswithabang/2017/06/16/was-it-all-just-noise-independent-analysis-casts-doubt-on-ligos-detections "Analysis of the data attributed the signal to...
  46. Pat Bannan

    Gas under pressure- disturbing noise recurring

    recently my neighbors and I have been awakened by a loud noise that sounds like something is being released under high pressure. An intense vibrating sound that lasts 30-45 seconds. We live across the steet from a soda manufacturer and down the road from a natural Gas transfer station. Both are...
  47. J

    A Calculate Third Octave Band Response from Narrowband Data

    I have a signal that I am able to calculate through an acoustic model for airfoil noise. I am told that the model solves for a narrowband frequency response, however, my measurement data is provided in third-octave band representation. How do I convert my current dataset to the third octave...
  48. V

    Maintaining the integrity of an analog signal

    Hi, I am measuring an analog voltage with an Arduino analog in. The analog voltage comes from a cable which also contains digital signal wires. Do I need to separate the analog and digital signals using separate cables? If so, does the analog voltage signal cable need shielding? And if so, how...
  49. Nikhil N

    How to choose an amplifier to couple the noise into data line

    Hii... I have to couple the noise into a communication cable for analyzing the performance of the communication. I am using a function generator which will generate a white noise of 1-2V(rms) and I have a current transformer to couple this to the communication line. The current transformer has...
  50. M

    MATLAB Eliminate Noise from an Image in MATLAB

    Hi PF! Attached is a binary image I have in MATLAB, where I have drawn an error pointing to some noise. Does anyone know of a systematic way to eliminate all noise below this line (or basically what appears to be the line)? I also uploaded the same image only processed, titled Noise1. This...
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