The vertical axis of each audio channel's track indicates the displayed range of the waveform view in the vertical dimension. The parameter shown on the vertical axis depends on the setting made in the menu View->Vertical Scale. Its visibility depends on the View->Vertical Rulers setting. By default, the linear amplitude is shown and indicated on the axis as percentage. In logarithmic amplitude mode, the lower and upper bounds are indicated in decibels. In sonagramme mode, the lower and upper bounds are indicated in hertz.
The vertical axis can be zoomed with keyboard shortcuts: Ctrl+Cursor Up to zoom-in (decrease amplitude span), Ctrl+Cursor Down to zoom-out (increate amplitude span). In logarithmic-amplitude mode, Ctrl+Alt+Cursor Up and Down change the noise floor of the display (the lowest decibels value displayed). In sonagramme mode where amplitudes are also displayed in decibels (corresponding to the hue and brightness of the pixels), the same shortcuts as in logarithmic-amplitude mode apply.
In time signal view (linear or logarithmic amplitude but not sonagramme), the amplitude is analyzed and displayed in two ways: As a momentary peak value (the maximum amplitude at one point in time) and as a momentary RMS value (the average energy at one point in time). The medium gray outer curvilinear area represents peak amplitude, the black inner curvilinear area represents RMS amplitude which is more closely linked to our perception of the loudness of a sound.