Cry analysis in infants with infectious and congenital disorders of the larynx.

Thirty induced pain cries from the same number of infants with infectious or congenital disorders of the larynx (infectious laryngitis, laryngomalacia, paresis of the recurrent nerve and subglottic stricture) have been analyzed by means of sound spectrography. For each cry 21 phonetic features have been evaluated. This cry material was then compared with 120 pain cries from healthy infants. In the pathological group a significant increase could be noted in the occurrence of the following cry attributes: second pause, abnormal melody types (rising, falling-rising, flat and no melody types), instability of the fundamental frequency, bi-phonation, vibrato, half-voiced voice quality, noise concentration, and inspiratory stridor. Furthermore, a significant decrease could be noticed in the occurrence of voiceless cries, falling and rising-falling melody types, and glottal roll. These findings show that such spectrographic features as very high maximum and minimum pitch, bi-phonation, gliding, and abnormal melody type occur more often in cries of infants with central nervous system involvement. Moreover, such parameters as instability of the fundamental frequency and noise concentration as indicators of neurologic disorders need further consideration. Except features of inspiratory stridor, this study revealed no really clear parameters typical of peripheral diseases of the vocal tract.