This is a report on perception aspects of a novel method of spectrography, developed as an aid for the deaf. By this method an animation is displayed on a screen, showing the time-frequency variations of an ongoing speech signal in real time. Here we evaluate the ability of human subjects to learn the animations for some multi-digit number utterances (such as telephone numbers). A recognition score of about 68 percent (where zero means chance expectation) was obtained through a number of forced-choice tests involving 2- digit up to 5-digit number utterances. The human subjects, being all beginners, took the tests after about only 30 minutes of training course. The results suggest a potential utility of the system for the deaf.