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; e.g., the 60-cycle frequency wave in an electrocardiogram; largely eliminated from modern (post-1980) machines (includes visual n. on imaging studies). See signal-to-n. 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]
- structured n. in radiology, the signals from anatomic structures that interfere with the detection of significant pathology.
- white n. a complex sound consisting of many frequencies over a wide band of frequencies; often used for masking of hearing in the nontest ear in the measurement of hearing.
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(noiz) unwanted variations in a signal that result from imperfections in the transmission of the signal, e.g., electrical signals in electrodiagnosis other than those being studied (most often originating within the electrical apparatus). See also signal-to-noise ratio, under ratio.Medical dictionary. 2011.