Units for logarithmic scales

APR 01, 1969

Even when successive effects are not additive but rather multiply each other (as do amplification and absorption), we need additive units for convenience. Here are suggestions for simplifying nomenclature and avoiding confusion.

DOI: 10.1063/1.3035525

Calvin S. McCamy

LOGARITHMIC SCALES ARE useful in many fields. Sound power attenuation, musical pitch, star magnitudes, photographic exposure parameters, hydrogen ion concentration and optical densities are all expressed on logarithmic scales, but how different the usages appear! As each technology satisfied its need in an ad hoc manner, the systems took on various peculiar forms. As a result, the essential equivalence of the forms is not generally recognized and the concepts and terminology are usually treated as special cases.

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References

1. W. H. Martin, “Decibel—the Name for the Transmission Unit,” Bell System Tech. J., Jan. 1929 p. 1.
2. A. G. Pikler, “Logarithmic Frequency Systems,” J. Acoust. Soc. Am. 39, 1102 (1966).https://doi.org/JASMAN
3. E. I. Green, “The Decilog: A Unit for Logarithmic Measurement,” Elec. Eng. 73, 597 (1954).
4. C. S. McCamy, “Concepts, Terminology, and Notation for Optical Modulation,” Photographic Science and Engineering 10, 314 (1966).

More about the Authors

Calvin S. McCamy. Image Optics and Photography Section, National Bureau of Standards.