Intensity discrimination for noise bursts in the presence of a continuous, bandstop background: effects of level, width of the bandstop, and duration.

Abstract

Weber functions for broad−band noise bursts were determined using a 2IFC procedure. Noise bursts were presented either alone or in the presence of a continuous, bandstop−filtered background whose spectrum level in the passband was 10 dB above that of the standard burst. The width of the bandstop was varied from 100 to 3160 Hz in half−log−unit steps. The center frequency of the bandstop was always 1800 Hz. Burst duration was either 10 or 250 msec, and levels ranged from 31 to 81 dB SPL. Weber fractions tended to increase with increasing level for all conditions using a bandstop background, but the effects were small. The form of the Weber function was similar for the long and the short duration bursts. Performance improved with increasing width of the bandstop, but the magnitude of the effect (on average, 2.5 dB per decade of bandwidth) was about half what would be predicted by stimulus−oriented models of discrimination (5 dB per decade). Subject Classification: 65.35, 65.50.