The effect of intervening sounds on pure-tone pitch recognition was investigated. Intervening sounds were (1) none, (2) pure tones, and (3) naturally spoken numbers uttered by a female and a male speaker. Nine subjects who possessed no absolute pitch were tested for (1) pure-tone pitch recognition, (2) serial recall of the spoken numbers, and (3) both pitch recognition and number recall. GLM analysis was performed on the arcsine transformed error rates. It revealed that, when the intervening sounds were numbers, the pitch recognition error rates were significantly increased for 4.6%--16.6% if number recall was also required, and vice versa (0.9%--16.6% increases in number recall error). Contrary to the previous notion [D. Deutsch, Science 168, 1604--1605 (1970)], these results indicate that a number recall task does interfere with pure-tone pitch recognition, and that speech sounds interfere with pure tones in auditory short-term memory. Although the pure tones caused larger pitch recognition interference than the spoken numbers for 2.8%--32.4%, this should be attributed to the fact that pitch of speech is less distinct than that of a pure tone.