Abstract:
Detection thresholds for broadband noise bursts were measured for 6 to 10-month-old infants and for young adults. The noise bursts were 500 ms in duration, repeated four times with 500 ms between bursts. The stimulus was presented monaurally using an insert earphone. Listeners learned to respond when they heard noise bursts, but not at other times. The probability that noise bursts would be presented on any trial was 0.5. A one-up, two-down adaptive procedure was used to estimate thresholds. The difference between the average infant threshold and the average adult threshold for noise bursts was 6--7 dB. This is in contrast to an average threshold difference of about 15 dB for a 1000-Hz tone [Bargones et al., J. Acoust. Soc. Am. 98, 99--111 (1995)]. Infants greater relative sensitivity for broadband noise is consistent with the hypothesis that infants do not listen selectively in the frequency domain. Immaturity of the middle ear and inattention may account for the difference between infant and adult thresholds for broadband noise. [Work supported by NIDCD DC00396.]