Duration and transition effects in multiple-burst, multitone masking

Abstract

Previous studies of tone detection using a multiple-burst same (MBS) or multiple-burst different (MBD) masker have shown that tone detection thresholds were lower with an MBD masker than with an MBS masker, and decreased as the number of bursts increased. In those studies, as the number of bursts increased, the total signal duration increased as well as the number of times the (MBD) masker changed frequencies. The present study was designed to differentiate between the effects of signal duration and masker transitions. In one condition, the burst duration was inversely varied with the number of bursts so that the overall stimulus duration was always 480 ms. In a second condition, the stimuli always had eight 60-ms bursts, but the number of times the masker transitioned from one random draw of frequencies to a different draw was varied from zero (MBS) to seven (MBD). The MBD condition showed a steady improvement with number of bursts, regardless of the burst duration. There was a similar improvement with the number of masker transitions. There was only a small improvement in thresholds with increasing burst duration. Results suggest that the number of changes of masker frequencies drives performance more than the total signal duration.