“…We measured seven parameters representing the aeroacoustic characteristics of sibilant /s/, which consist of autocorrelation coefficient, zero crossing count, and five spectral properties: F peak , F′ peak , S p , S′ p , and A d . The autocorrelation coefficient, which is the correlation between adjacent speech signals, is normally close to zero for unvoiced speech, such as sibilant /s/, although for the voiced speech, it is close to 1 because the speech waveform signals are correlated strongly (18). The zero crossing count indicates the frequency at which the energy is concentrated in the spectrum.…”