Study of changes in glottal vibration characteristics during laughter

Laughter in speech has been studied mostly relying upon the spectral representation like formants and harmonics derived from the short-time spectrum. Significant changes appear to take place in the characteristics of glottal source of excitation during the production of laughter, but these changes have not been explored much. In this study, we examine the changes in the glottal vibration characteristics in laughter production, using the electroglottograph (EGG) signals. The excitation source characteristics are also examined from the corresponding acoustic signal, using a modified zero-frequency filtering method. Changes are examined in three categories, namely, normal speech, laughed-speech and nonspeech-laugh. Results using both EGG and acoustic signals are similar. The closed phase quotient in each glottal cycle is observed to decrease more for nonspeech-laugh calls than laughed-speech, with reference to normal speech. Correspondingly, the instantaneous fundamental frequency, hence pitch, increases more for nonspeech-laugh.