Visual reinforcement audiometry (VRA) with insert-earphone stimulus delivery provides a means of obtaining early ear-specific information on the auditory status of infants. The aim of this study was to investigate the efficacy of VRA in young infants, and to compare the use of sound field and insert-earphone stimulus presentation. VRA was performed on 41 normally developing infants aged between 20 and 42 weeks. Infants were tested in the sound field (n=22) and with insert earphones (n=19). Results showed significantly more minimum response levels (MRLs) obtained with sound field testing, and with older children. Nevertheless, in the insert-earphone group, 36% of those aged 32 weeks or more gave two or more MRLs, and 25% of the infants aged 25 weeks or less gave one or more MRLs. This study provides data from developmentally normal infants which confirms the efficacy of insert-earphones as well as sound field VRA with 32-42-week-olds, with reasonable expectation of success. The data in this study also suggest that VRA could be usefully employed for younger infants aged approximately 20-26 weeks where information, although less easily obtained, may be of particular value to early diagnosis and habilitation.

The aim of this study was to determine normative values for minimal response levels (MRLs) for normal-hearing young infants using insert earphone visual reinforcement audiometry (VRA). The subjects were 46 normally developing infants aged between 33 and 50 weeks who had hearing sensitivity assumed to be within normal limits and no evidence of middle ear dysfunction. VRA was carried out using insert earphones with warble tone stimuli, generated from an AC33 audiometer and calibrated to ISO 389-2 for insert earphones in adults. The frequencies assessed were 500 Hz, 1 kHz, 2 kHz and 4 kHz. In total, 102 MRLs were obtained, with an approximately equal number of MRLs per frequency. Mean MRLs for 500 Hz, 1 kHz, 2 kHz and 4kHz were 16 dB HL, 13 dB HL, 7 dB HL and 6 dB HL, respectively. Standard deviations were close to 6 dB for all frequencies. Mean MRLs at the lower frequencies were significantly greater than MRLs at the two higher frequencies. MRLs did not vary significantly with age. The results obtained from this study suggest significant infant adult differences when testing hearing using VRA with insert earphones, particularly at lower frequencies. Possible reasons for this and the clinical use of these normative values are discussed.