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1. unwanted variations in a signal that result from imperfections in transmission; see also signal-to-noise ratio.
2. any disturbance in a visual signal being recorded in radiography; see also mottle.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


1. Unwanted sound, particularly a complex sound that lacks a musical quality because its various frequencies that comprise it are not whole-or-partial number multiples (harmonics) of each other. Compare: harmony.
2. Unwanted additions to a signal not arising at its source; for example, the 60-cycle frequency wave in an electrocardiogram; largely eliminated from machines after 1980 (includes visual noise on imaging studies).
3. Extraneous uncontrolled variables influencing the distibution of measurements in a set of data.
Farlex Partner Medical Dictionary © Farlex 2012


Random variation in signals of the electromagnetic spectrum that carries no useful information from the source.

A term defined in MRI as an undesirable background signal interference or other disturbance, which affects image quality.

Occupational medicine
OSHA requires that anyone with occupational exposure to greater than 89 decibels should wear ear protection.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Electronics Random variation in signals of the electromagnetic spectrum that carries no useful information from the source. See Cymatics, Music therapy, Sound therapy Technology Poisson noise Fluctuation in the number of information carriers–photons, electrons, which appears as 'snow' in a cathode ray tube, a function of the statistical variation of the rays received by the detector and number of electrons produced by the photomultiplier. See White noise. Cf Chaos, Pink noise.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


1. Unwanted sound, particularly complex sound that lacks a musical quality because the various frequencies of which it is composed are not whole or partial number multiples (harmonics) of each other.
2. Unwanted additions to a signal not arising at its source; includes visual noise on imaging studies.
See: signal:noise ratio
3. Extraneous uncontrolled variables influencing the distibution of measurements in a set of data.
[M.E., fr. O.Fr., fr. L.L. nausea, seasickness]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012

Patient discussion about noise

Q. what causes the sound of cracking noises in the head all the time it was said i had acute sinusitis but honestly i think it is more . I don't know why i have cracking noises in my head . I am very concerned about this also my neck is always stiff feeling and aching all the time. . My eyes are very tired and i see blue spots and they hurt behind the eye very badly . I have headaches very often

A. wow...that really sounds serious...i have chronic sinusitis and i can tell you i had horrible headaches but nothing like you describe now. i would strongly consider going to a hospital and checking it out...
tell us what was the result!

Q. Tinnitus (Ringing and Other Ear Noise) Anybody have this problem? Urrrrrrrrrrr, I think I want to shoot myself,you know what I mean. It is worst than the chinese torture. Someone, please send me a good tip how to stop it. I have this for 4 yrs and it is driving me crazy. You cannot enjoy total complete silence. They say silence is golden but not when you have this ringgi in your ears. It gets worst when there is no noise. The only remedy I have is eating hot spicy curry, it helps for 2-3 wks and then it comes back again and then eating spicy food again. Listening to classical music helps to. Oh well.....just have to suck it up.

A. I've read that lipoflavinoids can help.

Q. what can cause a migrane other than light, noise, andno sleep? Well its been 4 days n 3 nights that I have it n it dont go away it was bad at first but then my right ear hurted as well as my right upper wisdomteeth It seems to be in only the right side and its been movin down towards my neck... Please if u have any info on wha the fuck is goin on with me let me know asap...

A. A migraine attack can be triggered also by caffeine consumption, alcohol consumption, certain medications, allergic reactions, physical or emotional stress, smoking, skipping meals, menstrual cycle fluctuations, menopause, and certain food containing-
1) tyramine- red wine, aged cheese, smoked fish, chicken liver, figs and some beans.
2) nitrates - like hot dogs, bacon and salami.

More discussions about noise
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References in periodicals archive ?
It is acknowledged that an attacker may be able to collect many orders of magnitude more traces in order to reduce the noise floor such that the correlation is discernible to break the combined countermeasure configuration.
In order to know the limitations of the measurement method, it is necessary to obtain the minimum discernible value of phase noise at the system input, that is, the phase noise floor. This noise floor can be calculated by referring the power spectral density of the internal voltage noise, [S.sub.nn](f), which is usually referred at the detector output (as seen in Figure 4), to the system input.
The structure parameters are matched with the optimal design with low noise floor. A bit larger insertion loss compared with the numerical results (see Figure 5) is mainly due to the large scattering loss of the rough grating sidewall [1].
* Spectrum below the noise floor is therefore not scarce, at least
A masking system addresses these issues by distributing a background sound throughout the facility, raising the noise floor to a comfortable 42dBA to 48dBA, or higher where required.
The low noise floor results from a combination of the accelerometer's design and the use of feedback control.
In these patients, emission amplitudes were above the noise floor at all frequencies between 500 Hz and 8 kHz, and these responses were accepted by the system as valid.
All systems use HP's third-generation Test Processor-per-pin technology for the highest throughput and a low noise floor. Customers can use HP's Pay-Per-Use technology to upgrade performance models on a temporary or permanent basis, allowing flexibility and minimum risk.
Bernardsville, NJ, May 03, 2019 --( Zero Feedback, Zero Dead time and bottomless noise floor using Gallium Nitride (GaN) transistors on the ELEMENT 114 Stereo Power Amplifiers from Merrill Audio make it simply one of the best amplifiers available.
The Infiniium UXR Series provides 10-bit resolution, four full-bandwidth channels to reduce timing error when working with dual-polarization coherent modulation, full self-calibration to ensure ongoing measurement accuracy while eliminating the need to take the unit out of service, and chipset based on a the vendor's proprietary InPprocessthat enables wide bandwidth and low noise floor. Keysight Technologies,
Unique features include: reduced footprint, ease of installation, low RF noise floor, and industry-leading value pricing.
Key features are multiple sensitivity options, wide-band frequency response, hermetic sealing, signal ground isolation from case, a low noise floor, TEDS capability (IEEE P1451.4) and a CE mark.