The displacement of a threshold from its measured-in-the-quiet value to the value it takes in the presence of another sound is masking. Measurement of that displacement is masking audiometry. Measurement of displacements at a large number of frequencies produces a masking pattern. This paper concerns itself with a procedure that produces masking patterns with good precision, sensitivity, and rapidity without the problems of tonal interference and beats that normally complicate the determination of masking patterns. Several applications of the technique are suggested, including diagnostic audiometry, continuous-frequency SAL testing, a testing system for ear protectors, and a device for measuring the masking effects of various complex noises and tones.