The just noticeable difference of early decay time (EDT)

Abstract

The purpose of this study was to determine the just noticeable difference (JND) of early decay time (EDT) for broadband conditions and individual frequency bands. JNDs of room acoustic parameters are important for assessing if changes in geometry or materials in a room will have a discernible impact in the listener’s perception. The EDT JND has been reported to be 5% in the ISO 3382-1:2009 standard, which is the same value usually quoted for the JND of classical reverberation time (T30). No formal studies have been undertaken so far to validate if this JND value is appropriate for EDT, or to determine its dependency on frequency. Measured spatial room impulse responses (SRIRs) from three concert halls were used as base cases, which were then modified with a computer algorithm to attain specified values of EDT. All stimuli were reproduced in an anechoic chamber with an array of 30 loudspeakers using third-order ambisonics. The method of constant stimuli, in which a psychometric function is fitted to the measured data, was used to determine the JND. Thirty subjects with musical backgrounds participated in the study. The obtained broadband JND was 26%, while individual frequency band JNDs were higher.