Korean has two types of alveolar fricatives called "lax" and "forced". We observed the acoustic characteristics of each type of fricative with a sound-spectrograph. At the beginning and in the middle point of the frictional period, both types of fricatives showed a similar spectral pattern: the main frequency component was observed to be higher than 5000Hz in many cases among both types of fricatives. At the final point of the frictional period, a low frequency component around F2 and/or F3 of the following vowel was observed in the lax fricative more often than in the forced one. However, our results suggested that the presence or absence of the low frequency component around F2 and/or F3 of the following vowel might not differentiate the two types of fricatives.
