The degree to which the amplitude is uniform over a specified surface (typically either the output surface or the input surface). A uniformity of 1.0 (100%) is usually considered optimal.

Ignoring any asymmetry in the amplitude, the simplest calculation of uniformity is —

\begin{align} \label{eq:14301a} \widehat{U} = \frac{\overline{U}_{min}}{\overline{U}_{max}} \end{align}

where —

\( \widehat{U} \) = uniformity
\( \overline{U}_{min} \) = average minimum axial amplitude on a specified surface
\( \overline{U}_{max} \) = average maximum axial amplitude on a specified surface

The average minimum amplitude and average maximum amplitude are from symmetric locations (respectively) on the specified surface.

Details —
Uniformity — Basic Concepts
Uniformity & Asymmetry - Calculation

Also see —
Amplitude droop
Amplitude rise