The results of two complementary detection tasks using digitally synthesized noise are reported. In one experiment the bandwidth of the synthetic noise was varied to reveal the region most effective in masking a 1‐kHz signal. The bandwidth of the internal filter (’’critical band’’) so measured was about 80 Hz. In another experiment, a wideband noise was used as the masker for a synthetic signal whose bandwidth was varied to determine the maximum effective width of the internal filter. Although some earlier experiments suggest maximum effective widths as small as 180–200 Hz (around 1 kHz), the data reported here indicate the range of spectral integraton extends from the critical band to a maximum width that may exceed 3 kHz. In addition, the good agreement between the two experiments suggests a new method for estimating critical bandwidths based on the determination of two thresholds: that of a tonal signal in a wideband masker and that of a supracritical‐width noise signal in a wider‐bandwidth masker.