The probe-signal method (Greenberg & Larkin, 1968) was used to determine the percentage of trials in which unpracticed subjects detected (two-interval, forced-choice) a soft, expected sound as compared with an unexpected sound. Pure tones at or near an expected frequency were detected in about 90% of the trials. Tones more than one-half critical band away were detected near chance (50%). Complex sounds (a band of noise or a multitone complex) were detected better if they were inside the same critical band as the expected signal than if they were outside the band. A signal that differed spectrally from the expected sound was not detected even though it had the same low pitch, based on a common fundamental frequency. The results may mean that under some conditions focused attention alters sensitivity in the auditory system.