A unit used to express ratios, such as gain, loss, and relative values. Note 1: The neper is analogous to the decibel, except that the Naperian base 2. 718281828. . . Is used in computing the ratio in nepers. Note 2: The value in nepers, Np, is given by Np = ln (x1/x2,) where x1 and x2 are the values of interest, and ln is the natural logarithm, i.e., logarithm to the base e. Note 3: One neper (Np) = 8. 686 dB, where 8. 686 = 20/ (ln 10. ) Note 4: The neper is often used to express voltage and current ratios, whereas the decibel is usually used to express power ratios. Note 5: Like the dB, the Np is a dimensionless unit. Note 6: The ITU recognizes both units.