In the present study, we investigated the effect of a previous sound on loudness at the absolute threshold of hearing. The change in the absolute threshold of hearing was measured when a pure tone preceded the test tone for the measurement of the threshold. The previous sound at 60 dB SPL was presented first in one ear, followed by the presentation of the test tone in either the contralateral or ipsilateral ear after an interval of 0.5 s. Both the previous and test sounds had the same frequency, 500 Hz, and the same duration, 3 s. The change in threshold was obtained from the difference between the thresholds with and without the previous sound. As a result, the threshold was found to decrease significantly by approximately 2 dB when the previous sound was presented in the contralateral ear. On the other hand, the threshold was only slightly changed when the previous sound was presented in the ipsilateral ear.