Abstract: There is disclosed a method for generating a low-frequency sound program for play during the performance of a motion picture film to produce a physical effect on the theater audience. Rather than to use random low-frequency noise or some other low-frequency source which is unrelated to the audible sound program, the low-frequency program is derived by shifting down in frequency a selected portion of the audible sound program. The final low-frequency program contains frequency components below 40 Hz, at least 50% of the total energy of which is derived from the shifted-down audible program. By so harmonically relating the audible and low-frequency programs, the audio/visual and vibrational sensations are perceived in a less disjointed fashion.