The effects of different test methods on the just noticeable difference of clarity index for music

A study of the just noticeable difference of early decay time for symphonic halls

The just noticeable differences (JNDs) of room acoustic parameters are important for the design of concert halls and, in general, research of room acoustics. Precise knowledge of JNDs helps the concert hall designer in assessing the impact that changes in the geometry or materials of the hall will have on its perceived acoustics. When designing a concert hall, creating an appropriate feeling of reverberance for the audience is of prime importance. The early decay time (EDT) parameter has proved to be a better predictor of the perception of reverberance than the classical reverberation time (T30), but no studies have been conducted to specifically determine the EDT JND. In the present study, the EDT JND was investigated for broadband conditions and assessed for individual frequency ranges. A subjective study was conducted with 26 subjects with musical training, in which 21 were considered reliable. The participants listened to orchestral music convolved with measured spatial room impulse responses from three concert halls. The stimuli were auralized in an anechoic chamber using third-order Ambisonic reproduction. The obtained values show that the JNDs for the broadband conditions are lower than those for the individual frequency ranges. The EDT JND for the broadband conditions was found to be approximately 18% of the EDT value.

Effects of test method and participant musical training on preference ratings of stimuli with different reverberation times

Selecting an appropriate listening test design for concert hall research depends on several factors, including listening test method and participant critical-listening experience. Although expert listeners afford more reliable data, their perceptions may not be broadly representative. The present paper contains two studies that examined the validity and reliability of the data obtained from two listening test methods, a successive and a comparative method, and two types of participants, musicians and non-musicians. Participants rated their overall preference of auralizations generated from eight concert hall conditions with a range of reverberation times (0.0-7.2 s). Study 1, with 34 participants, assessed the two methods. The comparative method yielded similar results and reliability as the successive method. Additionally, the comparative method was rated as less difficult and more preferable. For study 2, an additional 37 participants rated the stimuli using the comparative method only. An analysis of variance of the responses from both studies revealed that musicians are better than non-musicians at discerning their preferences across stimuli. This result was confirmed with a k-means clustering analysis on the entire dataset that revealed five preference groups. Four groups exhibited clear preferences to the stimuli, while the fifth group, predominantly comprising non-musicians, demonstrated no clear preference.