Method and apparatus for determination of gain margin of a hearing assistance device under test. In varying examples, the impulse response for multiple levels can be taken and used to arrive at a gain margin. The method and apparatus, in various examples, process critical portions of the resulting data for efficient processing and to increase accuracy of measurements. The method and apparatus performing a plurality of measurements to determine impulse responses and to derive gain margin as a function of frequency therefrom. The present subject matter includes principles which may are adapted for use within a hearing assistance device using a single white noise stimulus, according to one example. The principles set forth herein can be applied to occluding and non-occluding hearing device embodiments. Additional method and apparatus can be found in the specification and as provided by the attached claims and their equivalents.