title: Noisy but effective: crying across the first 3 months of life.
abstract: OBJECTIVE
  To evaluate the developmental occurrence of subharmonic (SH) and noise (N) phenomena and to quantify their extent in the spontaneous cries of healthy infants across the first 3 months.
  
  
  METHODS
  Populational prospective study.
  
  
  METHODS
  Spontaneous elicited cries from 20 infants (10 male) were repeatedly recorded across the first 3 months of life.
  
  
  METHODS
  Frequency spectra and waveforms were used to identify the occurrence of SH and N and to measure the percentage of their combined occurrence in overall monthly crying behavior (expressed as a quantitative noise index [NI]).
  
  
  RESULTS
  SH and N episodes were prevalent in the cries of young infants during the first 2 months, being present in more than 50% of the recorded cries. A developmental trend was evident in NI with a significant decrease across the 3-month period. A corresponding significant increase in mean duration of single cries was observed during the same period.
  
  
  CONCLUSIONS
  SH and phonatory noise are regularly occurring phenomena in healthy infant crying because of the characteristics of pediatric larynx anatomy and neurophysiological control mechanisms underlying cry production. The reduction in NI appears to correspond with the development of an infant's crying complexity. The utility of NI as a metric of cry phonatory behavior should next be validated on infant groups with known or suspected health problems.
authors.affiliation: Department of Orthodontics, Center for Pre-Speech Development and Developmental Disorders, University of Würzburg, Würzburg, Germany.
authors.forename: Ndemazeh Arnold
authors.initials: NA
authors.lastname: Fuamenya
authors.affiliation: Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Robb
authors.affiliation: Department of Orthodontics, Center for Pre-Speech Development and Developmental Disorders, University of Würzburg, Würzburg, Germany. Electronic address: wermke_k@ukw.de.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Wermke
mesh_terms: D000162:Acoustics; D000367:Age Factors; D003448:Crying; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010699:Phonation; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D013018:Sound Spectrography; D013997:Time Factors
keywords: Cry; Development; Fundamental frequency; Infant; Phonation; Phonatory noise; Subharmonic