Abstract: Signal-to-noise ratio and reverberation time are the important factors that influence the speech articulation in classrooms.There is no the consensus of opinion about the optimal reverberation time in classrooms while the consensus about the optimal lower limit of signal-to noise ratio is reached.Speech articulation tests have been done in various virtual classrooms where the reverberation times are different from each other.Variance of articulation index scores in each test are analyzed.And then the significant differences of means between group data are tested with the pair matching comparison method which is idiomatic in the field of experimental psychology.The analytical results show that the optimal reverberation time of mid frequencies in the classroom with a volume of less than 200 m³ and a signal noise ratio of higher than 20dBA is about 0.6 seconds.