Amplitude Axis Scaling
Two basic amplitude scaling types are linear and logarithmic. They are related by the following equations:
Linear value = 10 ^ (Log value/20)
Log value = 20 * Log10 (Linear value)
Linear amplitude scaling makes the largest components in a spectrum very easy to see and to evaluate, but very small components may be overlooked completely. Linear scaling may be adequate in cases where the components are all about the same size. Logarithmic amplitude scaling clearly shows the low level signals in the presence of stronger signals. Logarithmic scaling is the default.
Log Magnitude scaling uses linear units on a logarithmic scale.