Relation between Auditory Source Width in Various Sound Fields and Degree of Interaural Cross- Correlation: Confirmation by Constant Method

The purpose of this paper is to confirm the inference from an experiment reported in a previous paper (Morimoto, M., Iida, K. & Furue, Y., Applied Acoustics, 38 (1993) 291-301) that auditory source widths perceived in different sound fields with the same degree of interaural cross-correlation are equal to each other, regardless of the number and arriving direction of reflections. In this paper, the method of constant is used in the experiment, instead of the method of adjustment which was used in the previous paper. The results confirm the conclusion inferred in the previous paper. 1 I N T R O D U C T I O N A previous paper 1 investigated the question whether or not the degree of interaural cross-correlation could be widely applied as a physical factor to estimate auditory source width (ASW) perceived in any sound field. In that paper, results of psychological experiments inferred that ASWs perceived in different sound fields with the same degree of interaural cross-correlation are equal to each other, regardless of the number and arriving direction of reflections. But a definite conclusion could not be drawn, because of the bias of subjective judgment caused by the method of adjustment by a subject. In this paper, the same question is confirmed by using the method of constant. * Present address: Matsushita Communication Industrial Co. Ltd, Saedo, Midori, Yokohama 226, Japan. 233 Applied Acoustics 0003-682X/94/$07.00 © 1994 Elsevier Science Limited, England. Printed in Great Britain 234 M. Morimoto, S. Sugiura, K. Iida 2 E X P E R I M E N T The method of the psychological experiment performed in this paper was the method of constant, using the paired comparison test between the fixed test field with a constant degree of interaural cross-correlation and one of the variable comparison fields with different degrees of interaural cross-correlation. 2.1 Experimental conditions 2.1.1 Musical motif The motif used in this experiment was a six-second section from bar 94 of the fourth movement of Mozart 's Jupiter Symphony (No. 41), which was the beginning of the same motif used in the previous paper. 2.1.2 Apparatus Thirteen cylindrical loudspeakers (diameter 108 mm, length 350 mm) were arranged at horizontal angles of 0 °, +30 °, +45 °, ___60 °, __-90 °, +120 °, and ___150 ° from the median plane at 1.5 m distance. The loudspeaker at 0 ° radiated a direct sound and the other loudspeakers radiated reflections. The frequency characteristics of all loudspeakers were equalized within +2.5 dB in the frequency range from 100 Hz to 10 kHz by a digital frequency equalizer (Technics DSE-10). 2.1.3 Kinds of structure of reflections The structures of reflections of the variable comparison fields and the fixed test field are the same as those used in the previous paper. 1 Figure 1 shows the structure of reflections of the variable comparison field. The field consists of a direct sound and two reflections. The direct sound was radiated from the front of a subject and the reflections