The use of repeated presentations of a given signal event as an experimental technique in psychoacoustic studies provides information about several general properties of the hearing process. From the relationship between the gain in detectability that results from additional observations and the type of signal and noise employed, inferences can be made about: (1) the observer's ability to integrate over time, (2) the amount of noise generated by the auditory system, (3) the nature of the process of frequency analysis, and (4) the observer's mode of dealing with uncertainty as to signal frequency. The first set of experiments permitted five observations of each signal where the signal consisted of a pulsed tone, of known frequency, in noise. Both variable noise, i.e., noise that is statistically independent from one presentation to another, and constant noise, i.e., noise that is exactly the same on each of the five presentations, were used. With variable noise, the detectability index d′ improves, as predicted, as the square root of the number of observations. The use of constant noise, which results in less improvement, provides an estimate of the portion of the total noise affecting detection that is of internal origin. The results under different levels of external noise indicate that internal noise is proportional to external noise. A second set of experiments employed signals whose frequencies were unknown to the observers, and signals comprised of several widely spaced frequencies. Their results are discussed in relation to three alternative models of the process of frequency analysis.