Effects of Noise on Dichotic Temporal Resolution

The effect of broadband (125–8000 cps) background noise on the dichotic temporal interval between two clicks required to report them as two was investigated. As noise level is increased up to 30 dB SL (re monaural threshold), the dichotic temporal interval required for a report of two (Δt) is decreased. For noise levels from 30–50 dB SL, the dichotic temporal interval for a report of two increases. The extent of this reversal seems related to mask level, although the effect of noise in decreasing Δt is not related to signal-to-noise ratio. With narrow-band low-pass noise, the Δt required for a report of two continues to decrease as noise level increases up to 50 dB SL, whereas a narrow-band high-pass noise shows the same reversal as does the broadband noise. Increasing the click level without adding any background noise decreases the Δt required for a report of two. Additional experiments that elucidate these findings are presented.