neper

noun

1. A non-SI unit of the attenuation (or sometimes gain) of field and power quantities such as electronic signals; the natural logarithm of a ratio, with 1 Np (a ratio of 2.718:1) being equivalent to 8.686 dB.

   “Values of b, the amplitude attenuation constant, are given for various materials in Table 1.1. Having dimensions of [length]⁻¹, it is usually measured in nepers per centimetre (Np cm⁻¹).”

   “The unit of α is nepers per meter. It can be easily seen that if a line has an attenuation constant of 1 neper/m, a unit amplitude voltage wave will reduce to e⁻¹ over a distance of 1 meter.”

   “The attenuation constant for the phantom muscle tissue is αₘ = 10.0 nepers/m.”