Psychophysical structure of eight complex underwater sounds.

The potential usefulness of multidimensional scaling techniques in the perceptual analysis of ’’real world’’ underwater sounds was demonstrated. Nineteen observers (nine with musical training, ten without) used a five‐point scale to judge the similarity of all possible pairs of eight passive sonar recordings. The eight s signals were selected to represent a range of common natural and man‐made underwater sounds. These data were analyzed using the INDSCAL multidimensonal scaling model, revealing an interpretable two‐dimensional psychological space. One of the psychological dimensions was interpreted as reflecting the overall shape of the 1/3‐octave spectra of the eight signals, while the second was seen to reflect the prominence of a low‐frequency periodicity present in some signals. Individual observer analysis revealed substantial differences between the musically trained and musically inexperienced observers in the relative importance or salience of the two dimensions. The relation of these findings to earlier work was discussed.