nepern.
/ˈniːpə/, /ˈneɪpə/, U.S. /ˈnipər/, /ˈneɪpər/ A unit of measurement used in comparing voltages, currents, power levels, or other quantities (and esp. in measuring attenuation over telecommunications transmission lines), the difference in nepers between two values being equal to the natural logarithm of their ratio (for voltages and currents) or to half of this (for power differences). Abbreviated Np.One neper is equal to 8.686 decibels.
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the world > matter > physics > science of sound > [noun] > instrument measuring intensity > unit comparing intensities
neper1922
society > communication > telecommunication > telegraphy or telephony > telephony > [noun] > unit of attenuation or intensity
standard cable1905
neper1922
decibel1928
bel1929
1922 Proc. National Acad. Sci. U.S.A. 8 191 At levels of loudness from 1 to 10 napiers above the threshold (one napier corresponds to a pressure ratio of e to 1) phonometric comparisons were satisfactorily made.
1929 W. H. Martin in Bell Syst. Techn. Jrnl. 8 2 It was further suggested that the naperian unit be called the ‘neper’ and that the fundamental decimal unit be called the ‘bel’, these names being derived from..Napier..and Alexander Graham Bell.
1954 Electronic Engin. 26 91 The short line with which we are concerned in this article is defined as one for which the overall attenuation coefficient is small, say not greater than 0·2 neper, although the line may be several wavelengths long.
1994 Philos. Trans. (Royal Soc.) A. 346 334 In the inverse-square expression for the cross-spectral density of the noise, the attenuation coefficient, β, is in nepers per metre.
This entry has been updated (OED Third Edition, September 2003; most recently modified version published online March 2022).
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n.1922