whereas the decibel was originally defined in terms of power ratios. A power ratio 10 log r dB is equivalent to a field-quantity ratio 20 log r dB, since power in a linear system is proportional to the square (Joule's laws) of the amplitude. Hence the decibel and the neper have a fixed ratio to each other:
:and
:

The (voltage) level ratio is
:

Like the decibel, the neper is a dimensionless unit. The International Telecommunication Union

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