Some Factors Influencing the Effective Auditory Intensive Difference Limen

Abstract

Observers were required to detect changes in intensity in signals of two types: (1) a continuous Gaussian noise to which increments were added randomly and infrequently; (2) a sequence of pulses, 0.5-sec duration occurring periodically at 2.5-sec intervals to which increments were added infrequently and randomly. For each of the types of task, several levels of discrimination difficulty were employed. It was found that the changes in intensity of the steady noise were more readily detected than comparable changes in intensity of pulses. At intermediate difficulty levels, the number of detections of increases in the steady signal declined with time on task; and, at intermediate and high difficulty levels, the number of detections of louder pulses declined with time. Progressive increases in response latency were also noted in some of these conditions, and there was a general tendency of false detections to decline with time on task. Possible explanations for the differential discriminations of changes in intensity of the steady and pulsed stimuli are discussed.