Temporal integration in the presence of off-frequency maskers

Temporal integration was measured at a relatively low and a relatively high signal frequency under conditions of off-frequency masking. The masker was typically gated for 300 ms, and the signal was presented 70 ms after maske r onset. In experiment 1, the signal frequency was 500 or 2000 Hz. Temporal integration was measured in quiet and in the presence of a masker whose fr equency was lower or higher than the signal frequency. in all listening sit uations, there was less integration at 2000 Hz than at 500 Hz. This effect of frequency was particularly dramatic in the presence of a. lower frequenc y masker, where there was almost no integration at 2000 Hz. Experiment 2 sh owed that this dramatic effect of frequency cannot be understood in terms o f the underlying psychometric functions. Experiment 3 measured temporal int egration at 750 and 2000 Hz for a large number of masker-signal frequency s eparations for both a tonal and a noise masker, and in conditions where the masker was gated or continuous. The results with the gated tonal masker la rgely confirmed the results of experiment 1. The results with the continuou s tonal masker and the gated or. continuous noise masker, however, were qui te different. Ln those cases, the amount of temporal integration at both si gnal frequencies was more or less independent of the masker-signal separati on: the masked temporal integration was nearly equal to the integration in quiet. Thus based on the conditions evaluated here, off-frequency masked te mporal integration differs substantially from integration in quiet only for gated tonal maskers located considerably lower in frequency than the signa l. It is unclear how to account for this finding, although it may be relate d to attentional factors. (C) 2000 Acoustical Society of America. [S0001-49 66(00)02102-0].