This experiment examined the effects of forward masking (FM), backward masking (BM), continuous masking (CM) and absence of masking (UM) on just noticeable differences (JNDs) of sound frequency. JNDs were calculated for 3 normal hearing participants by asking participants which tone they thought was higher pitched: a tone with a masker before (FM), after (BM), or during (CM) the masked tone or the reference tone. The results showed that masking had a statistically significant effect on JNDs of frequency (p = .005). Multiple comparisons indicated that both the CM and BM conditions performed poorer than the UM condition. These results comply favorably with past research. Future research could explore the negative correlation established in past research to determine whether statistically significant differences between FM and BM/CM/UM conditions could be calculated.