A study of the just noticeable difference of early decay time (EDT)

The just noticeable difference (JND) for reverberation time (T30) and early decay time (EDT) has been reported to be 5%, but limited research has been done to support this value. Also, there are no indications as to how this JND varies with frequency. Preferred values of EDT for symphonic music and how they should vary with frequency are also missing. A subjective study was performed to determine the JND of EDT over several octave bands, using room impulse responses (IRs) measured in concert halls with an Eigenmike 32-element spherical microphone array and reproduced in an anechoic chamber with a three-dimensional array of 30 loudspeakers. IRs measured in several North American halls were employed as a reference and compared with stimuli in which EDT values were artificially modified in a specific octave band. Alterations in these IRs were controlled to introduce minimal changes in other subjective impressions, in particular clarity and spatial impression. The measured JNDs will set the groundwork for obtaining preferred values for this metric.