Effective attenuation of signals in noise under focused attention.

When attending to a tone at a given frequency, listeners are most sensitive to that tone and others within a restricted band of frequencies surrounding it. This region of enhanced sensitivity defines the attention band that was measured in two experiments using a modified version of the probe-signal method of Greenberg and Larkin [J. Acoust. Soc. Am. 44, 1513-1523 (1968)]. Experiment 1 showed that at five center frequencies, from 0.25 to 4.0 kHz, the shape of the attention band resembles that of the auditory filter as inferred from notched-noise masking experiments by other investigators. The width of the attention band is close to the critical band at higher frequencies, but only half as wide at 0.25 and 0.5 kHz. Experiment 2 produced psychometric functions for unattended probe tones at least 0.23 kHz away from a fully attended, 1-kHz target tone. From these functions, the effective attenuation, measured as the threshold difference between the 1-kHz target and the probes, was estimated to be 7 dB; the amount of attenuation appeared to be about the same regardless of how far the probe frequency was from the attended band. One interpretation of these results is that bands centered on the unattended tones contribute to the decision process with some small but measurable weight and are not entirely ignored.