Linear Amplitude

Linear amplitude, as the name might imply, is amplitude displayed on a linear scale, e.g., volts or digital integer-based amplitude units. In Smaart, the only places that you ever see linear amplitude are linear time-domain charts, where amplitude is displayed as a percentage of normalized full scale. That is to say that the largest positive and negative numbers obtainable from a signed integer of given number of bits (e.g., 16 or 24 bits per sample) are scaled to a range between 1 and -1 (inclusive), with fractional values in between expressed as percentages.

Since you can’t take the log of a negative number, the only way to see relative polarity in an impulse response is to use a linear amplitude scale. Also, some people prefer the linear amplitude scale for identifying discrete reflections in an impulse response, and it can be useful for looking at other types of signals as well. A linear amplitude scale tends not be very useful for looking at reverberant decay or for identifying peak structures in the LF range of an impulse response where the length of a waveforms period is spread out of time so much that a clear impulse is not easily discernible. 

Linear vs Logarithmic amplitude scaling. The impulse response of a bandpass filter is shown on a linear (percentage of normalized full scale) versus logarithmic (decibel) amplitude scale. Notice that only the first two oscillations in the IR are easily discernible on the linear (Lin) view, whereas the Log view clearly shows the first six corresponding lobes.