[A study of the auditory responses to intra-uterine sound in the first few months after birth].

The auditory responses of infants until 3 months after birth were examined using the doll "Nenkororin" which contains a tape recorder of the intrauterine sound (IUS). The purpose of this study was to assess the applicability of these responses to screening of infants with severe hearing impairment. The results are summarized as follows. 1. The IUS with 1/3-octaval audiofrequency of 400Hz-4kHz was presented to 152 neonates. Positive responses showing alert inactivity were obtained in 148 infants, but negative responses in 2 neonates. 2 infants were undetermined. The neonates showed negative responses had severe hearing impairment with comparison of ABR. ABR was also carried out in 69 of the 152 infants. The results of ABR well agreed with those of the IUS test. 2. A typical reaction of neonates who stopped crying and assumed a state of alert inactivity in responses to the IUS was demonstrated until approximately one month after birth. At the end of the first month after birth, the threshold of this reaction grew smaller than that of the one-week period after birth. The latent time of this reaction also tended to become shorter. 3. The infants mostly failed to respond to the 1/3-octaval noise consisting of 0.5, 1.0, 2.0, 4.0kHz extracted from the IUS. From the experiment using high and low pass noise components extracted from the IUS. High response were obtained at low frequency band components below 1kHz. 4. Public health nurses without experience of auditory test were requested to compare the reaction by the IUS test and an auditory reflex test using tongue-clicking, whistling and paper-crumpling sounds. The IUS test was found to be easier for evaluation of the reactions than the other method of test. From the above results it is concluded that the auditory response to the IUS was useful for screening of severe hearing impairment in neonates until one after birth.