Controls of a modulated delay time of reflection enhancing subjective preference

Abstract

Previously, the most preferred delay time of reflection for time-invariant sound fields corresponds to the effective duration of the autocorrelation function (τe) of source signals [Ando, Concert Hall Acoustics (Springer-Verlag, New York, 1985)]. However, the SPL fluctuation in a real room is fluctuated and the model of such a time-variant system is proposed by the direct sound and the varying delay time of reflection [Ueda and Ando, J. Acoust. Soc. Am. 102, 2771–2775 (1997)]. To realize more excellent sound fields than time-invariant sound fields, a method of controlling a modulation of the delay time of reflection is discussed. Experiments are performed on the modulation methods to enhance subjective preference in a sound field. The following methods are examined to control the delay time of reflection in the experiment: (1) sinusoidally modulated delay time, (2) random modulated delay time, (3) delay time corresponding to the change of the running τe of the source signal, and (4) fixed delay time of reflection at the minimum value of the running τes.