The ratio of relevant to irrelevant information in a display. The highest possible signal-to-noise ratio is desirable in design.

All communication involves the creation, transmission, and reception of information. During each stage of this process, the form of the signal is degraded, and extraneous information—noise—is added. Degradation reduces the amount of helpful information by altering its structure. Noise reduces clarity by diluting useful information with useless information. The clarity of information can be understood as the ratio of remaining signal to added noise. For example, a graph with no extraneous elements would have a high signal-to-noise ratio whereas, a diagram with many outer parts would have a low signal-to-noise ratio. A good design aims to maximize signal and minimize noise, thereby producing a high signal-to-noise ratio.

Minimizing noise means removing unnecessary elements and minimizing the expression of necessary details. It is essential to realize that every unnecessary data item, graphic, line, or symbol steals attention from relevant elements. Such extreme elements should be avoided or else eliminated. Necessary elements should be minimized to the degree possible without compromising function. For example, the expression of lines in grids and tables should be thinned, lightened, and possibly even removed. Every element in a design should be expressed to the extent necessary but not beyond the extent necessary. Excess is noise.

Seek to maximize the signal-to-noise ratio in design. Increase signal by keeping plans simple and selecting design strategies carefully. Consider enhancing critical aspects of information through techniques like redundant coding and highlighting. Use well-accepted standards and guidelines when available to leverage conventions and promote consistent implementation. Minimize noise by removing unnecessary elements and minimizing the expression of factors.

See also Alignment, Horror Vacui, Layering, Performance Load, and Propositional Density.
The signal-to-noise ratio of each of these representations on the left is improved by removing elements that do not convey information, minimizing the expression of remaining parts, and highlighting essential information.