Measurements of the just noticeable difference for reverberation time using a transformed up–down adaptive method

This investigation sought to measure the just noticeable difference (JND) for reverberation time (T30) using a rigorous psychophysical method, namely the transformed up-down adaptive method. In ISO 3382-1:2009, the JND for reverberation metrics is taken to be 5%, based on work by Seraphim (1958); however, others have suggested that the actual JND is higher. In this project, sound samples with varying T30 were auralized from impulse responses simulated in a realistically modeled performance space using ODEON. The model’s absorption coefficients were uniformly varied across all surfaces and frequencies to achieve the desired T30s. Three reference reverberation times were utilized (one, two, and three seconds), and eight T30 cases spaced at 4% intervals both above and below each of the three reference T30s were created. Auralizations using a 500 ms white noise burst were presented in a computer-based testing program running a three-interval one-up two-down forced choice method, presented in a sound booth over headphones with flat frequency response. The program randomly interleaved six staircase sequences, three of which ascended and three of which descended towards each reference T30. Results averaged across 30 participants will be presented. [Work supported by a UNL UCARE Grant and the ASA Robert W. Young Award.]