The method of limits estimates thresholds by averaging ascending and descending detection levels

Evidence

Regarding threshold estimation, however, a more commonly adopted classical method is the method of limits. In the ascending method of limits, the stimulus is first presented at an inaudible level, and the experimenter gradually increases the stimulus level until the listener is able to perceive it. On the other hand, the descending method of limits starts at an audible stimulus level and the experimenter decreases the stimulus level until it is not detectable. Averaging these two levels, then, yields the listener’s threshold. Experimentally, it has been found that listeners can anticipate stimulus presentations or become accustomed to hearing a stimulus (habituation). — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 295