Preferred Rate and Extent of the Frequency Vibrato

Abstract

The purposes of this study were, first, to determine listener preferences for rate and extent in the frequency vibrato of a complex tone at each of five octave levels in the equal-tempered scale; and, second, to discover the manner in which preferences varied with the listeners' musical training or auditory capacity. The complex tone employed at each level was generated by a multivibrator unit. This tone was electronically modulated with rates of 5.5, 6.0, 6.5, and 7.0 pulsations per second; the extents of modulation were 0, 0.10, 0.25, and 0.40 of a step. By combining each rate with each extent, twelve vibrato tones and one “straight” tone were obtained. These tones were presented for preference judgments by the method of paired comparisons. The subjects were divided into two categories: (1) individuals with little or no formal musical training as determined by answers on a personal questionnaire (N = 331), and (2) individuals with sufficient musical training and ability to be members of the University of Iowa symphony orchestra or chorus (N = 54). Rank order scales of vibrato preference were obtained for these two groups. In addition, preference scales were obtained for untrained subjects according to their ability to discriminate pitch, time, and timber as determined by tests from the Seashore battery. A comparison of the preference scales for untrained individuals indicated that (a) an extent of 0.25 step was preferred over a wide portion of the equal-tempered scale, (b) rates of 6.0, 6.5, and 7.0 pulsations per second were about equally preferred over the same range, and (c) native auditory ability had little effect on vibrato preference. The trained musicians tended to prefer the same rates of 6.0 and 6.5 pulsations per second as did non-musicians, but the musicians favored a narrower extent (0.10 of a step).