Abstract: The influence of various rhythmic sounds on the discrimination of intermittent light with lower, medium and higher frequencies were studied experimentally. Four types of rhythmic sounds were used: 1) tempo synchronized with the flash frequency; 2) tempo with no fixed relation to the flash frequence; 3) constant tempo, and 4) tempo proportional to the flash frequency.1. The synchronized sound tempo showed positive influence on the discrimination, which exhibited more strikingly with the increase of the flash frequency. Tempo with no fixed relation showed negative influence, but the influence decreased with the increase of the flash frequency. Positive influence of the constant tempo on the medium flash frequency was slightly higher than that on the lower frequency. The influence of the proportional tempo on the higher flash frequency was not significant. These findings suggested that the rhythmic sound influenced the discrimination of flash frequency through time perception.2. The discrimination of the lower flash frequency depended more on some auxiliary means, such as counting; and that for the higher frequency depended more on direct perception; with the medium frequency as a transitional stage.3. The DL of the time interval occupied by a single cycle in the intermittent light, obtained in this experiment, was lower than that obtained by authors who did not use flash light in their studies. This suggested that the summation of sensation should be taken into consideration in the determination of differential limen.

Key words: NULL