Detection of pure tones in quiet and in noise by infants and adults

Abstract

Detection thresholds in quiet and in noise were estimated for infants (6 months and 12 months) using the visually reinforced headturn procedure. Test stimuli were 1000- and 4000-Hz pure tones, presented monaurally (TDH-49). In the masking condition, white noise was continually present at the earphone at 63.5 dB SPL (No = 25.5 dB). An adaptive threshold estimation procedure with a 5-dB step size was used. An adult group was run using the same protocol as used for the infant groups. Adult data agree with existing detection estimates. Detection thresholds improve with age in each condition of this experiment. The difference between infant groups is consistent at each frequency in quiet and noise. In quiet, the infants were relatively more sensitive at 4000 Hz while adults were relatively more sensitive at 1000 Hz. In noise, detection thresholds vary with frequency in the same way for all groups. Inferred bandwidths (Sm/No) are much larger for infants than adults. Age-related differences in task performance suggest that nonsensory factors may influence these data.