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.
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.
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.
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.
Procedures for measuring sound localization, sound lateralization, and binaural masking level differences in young children were developed. The modified tests were administered to large groups of children aged between 4 and 9 yr and results showed that the procedures were suitable for testing children from the age of 4 to 5. Furthermore, on these binaural hearing tests 5-yr-old children performed similar to adults. Differences between 4-yr-olds and older subjects on localization and BMLD, or between 4 to 9-yr-olds and adults on lateralization were probably attributable to both a development in binaural hearing and to nonauditory factors.
1ExpORL/Department of Neurosciences, K.U. Leuven, O&N2, Herestraat 49 bus 721, Leuven, Belgium; 2University Department of ORL, Antwerp University Hospital, Antwerp University, Wilrijkstraat 10, Edegem, Belgium; 3Department of ORL, AZ. St. Augustinus, Oosterveldlaan 24, Wilrijk, Belgium; 4Department of ORL, UZ Leuven, Kapucijnenvoer 33, Leuven, Belgium; 5Department of ORL, Ghent University, De Pintelaan 185, Ghent, Belgium; 6Service ORL, Clinique St-Luc-UCL, av Hippocrate 10, Bruxelles, Belgium; and 7CORA-CI, Borggravevijverstraat 9, Hasselt, Belgium.
This work was supported by Research Foundation—Flanders (FWO Vlaanderen): project G.0568.05 and FWO-aspirant grant (first author).
Address for correspondence: Lieselot Van Deun, ExpORL, Department of Neurosciences, Herestraat 49, bus 721, 3000 Leuven, Belgium. E-mail: email@example.com.
Received January 15, 2007; accepted September 12, 2008.