title: Sound localization, sound lateralization, and binaural masking level differences in young children with normal hearing.
abstract: OBJECTIVE
  In this study, procedures for measuring sound localization, sound lateralization, and binaural masking level differences (BMLDs) in young children were developed. Sensitivity for these tasks was assessed in large groups of children between 4 and 9 yr of age to investigate potential developmental trends.
  
  
  METHODS
  Sound localization was measured in the sound field, with a broadband bell-ring presented from one of nine loudspeakers positioned in the frontal horizontal field. A group of 33 children between 4 and 6 yr of age and 5 adults took part in this experiment. Sound lateralization based on interaural time differences was measured with headphones in 49 children between 4 and 9 yr of age and 10 adults. A low-frequency stimulus containing harmonics 2 to 5 from a click train with a rate of 160 Hz was used. In the BMLD test, the same filtered click train was presented diotically or dichotically (phase reversed or time delayed) in a broadband (200 to 1000 Hz) frozen noise to 23 children between 4 and 6 yr of age and 10 adults. For comparison with literature, additional measurements with a 500-Hz sinusoid were administered to adults. All tasks were adapted to the interest and attention span of young children.
  
  
  RESULTS
  Children of 5 yr of age did not perform significantly different from adults on the sound localization task, but mean absolute errors were larger for the 4-yr-olds. Also on the BMLD task, 5-yr-old children performed at the adult level, whereas the 4-yr-old children obtained significantly less binaural unmasking compared with the adults. Concerning sound lateralization, a small but significant difference between adults and children existed, but no age effects were apparent in the 4- to 9-yr-old group. Overall, the variation was relatively large in the 4-yr-old group, with some of the children performing at adult level, in all three tasks.
  
  
  CONCLUSIONS
  The results of this study show that the modified procedures are suitable for testing children from the age of 4 to 5 yr. Furthermore, it seems that binaural hearing capacities of the 5-yr-olds are similar to those of adults. Several observations led to the hypothesis that the observed age differences between 4-yr-olds and older subjects on localization and BMLD or between those 4- to 9-yr old and adults on lateralization, were attributable to both a development in binaural hearing and to nonauditory factors, such as task comprehension, attention, and testing conditions. It is possible that the developmental process is more obvious and prolonged in other aspects of binaural hearing, which require more dynamic or more central processing.
authors.affiliation: ExpORL/Department of Neurosciences, KU Leuven, O&N2, Herestraat 49 bus 721, Leuven, Belgium. lieselot.vandeun@med.kuleuven.be
authors.forename: Lieselot
authors.initials: L
authors.lastname: Van Deun
authors.forename: Astrid
authors.initials: A
authors.lastname: van Wieringen
authors.forename: Tim
authors.initials: T
authors.lastname: Van den Bogaert
authors.forename: Fanny
authors.initials: F
authors.lastname: Scherf
authors.forename: F Erwin
authors.initials: FE
authors.lastname: Offeciers
authors.forename: Paul H
authors.initials: PH
authors.lastname: Van de Heyning
authors.forename: Christian
authors.initials: C
authors.lastname: Desloovere
authors.forename: Ingeborg J
authors.initials: IJ
authors.lastname: Dhooge
authors.forename: Naïma
authors.initials: N
authors.lastname: Deggouj
authors.forename: Leo
authors.initials: L
authors.lastname: De Raeve
authors.forename: Jan
authors.initials: J
authors.lastname: Wouters
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001309:Auditory Threshold / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006309:Hearing / Q000502:physiology*; D006801:Humans; D008297:Male; D008954:Models, Biological; D010470:Perceptual Masking / Q000502:physiology*; D012016:Reference Values; D013017:Sound Localization / Q000502:physiology*; D055815:Young Adult