Noise bands simulating passive sonar sounds were varied in terms ofspectrum(band passed from 150–600 cps, or 600–2400 cps, or 2400–9600 cps); in terms of amplitude modulation (simulated screw beats) atbeat ratesof 0, 3, 5, or 11 per second; and in terms of presence or absence ofaccentwithin a group of 4 beats. Every combination of these parameters (21 in all, not 24, since at zero beat rate there can be no accent) was rated by 20 subjects in terms of their aurally perceived characteristics on 15 scales representing seven different dimensions.Analysis was made of the manner in which the 21 sounds clustered within the space defined by the seven psychological dimensions. Two major clusters of sounds were observed, differentiated primarily on the basis of band pass condition (high frequencyvslow frequency). Exceptions to this general rule were analyzed to reveal the interactions between band pass condition, beat rate, and accent.