The aortic ejection click and the first heart sound (S1) are described in the time and frequency domains from computer processed phonocardiogram data obtained from 13 valvar aortic stenosis patients and 6 normal ones. The interactive FOBTRAI program developed was capable of the following: (1) computing averages, aligned averages, power spectra of selected segments, envelograms, and deterministic signals; (2) storing and retrieving intermediate results; and (3) plotting data. The program is listed and its interaction is fully described in this thesis. The following steps were used to analyze the data: (1) the determination of the click onset times; (2) the generation of aligned average cardiocycles for both the click and S1; and (3) the calculation of power spectra for selected segments of the click and S1. The tabulated results typically show 2 frequencies in 51 and 3 in the click, with the click being distinguished by an oscillation between 160 and 230 Hz. Characteristics of the click versus time are also tabulated. / Master of Science