Fig. 7. The 75% discrimination threshold for hemisphere sizes plotted for different echo parameters. (A) Just-noticeable difference in sound pressure level, (B) just-noticeable difference in duration of the time gap between first and second reflection (gap_1-2) of the impulse response of the echo and (C) just-noticeable change of the spectrum. Arrowheads indicate the position of the mean (). The black circles mark values derived from Schmidt (Schmidt, 1992).