Short duration auditory fatigue, i.e., the temporary shift in the threshold of hearing following the cessation of a masking source, may be termed “residual masking.” In this study, curves of residual maskingvsfrequency have been obtained in a free‐field in the low‐frequency range, for 250‐cps masking tones at sound pressure levels of 90 and 110 db, following the method of Munson and Gardner. These masking patterns were obtained 150 and 200 msec after the cessation of the masking tone. In addition, residual masking at 250 cps was measured as a function of the mel‐band intensity level of a “white noise” masking source. Plots of loudness densityvsfrequency were computed from residual masking patterns, and the loudness of the pure‐tone masking source was evaluated.