Amplitude droop

A condition in which the amplitude at a specified location is less than the amplitude at a reference location, both amplitudes being measured on the same surface and in the same direction. An entire surface (e.g., the face) is said to have amplitude droop if the amplitude everywhere is less than the amplitude at the reference location.

Unslotted bar horns and cylindrical resonators will have amplitude droop on their faces (for the axial amplitude, measured with respect to the amplitude at the center of the face) unless corrective measures are taken (e.g., adding flanges.)

Also see —
Amplitude rise
Uniformity.