Behavioral audiometry: protocols for measuring hearing thresholds in babies aged 4-18 months.

OBJECTIVE

This paper provides the first report in English of original behavioral audiometry protocols for measuring hearing thresholds in very young children, including the multiply handicapped.

METHODS

Based on reactions to one or two well-calibrated acoustic stimulations delivered in the sound field, the protocol first involves the use of a vibrator to measure hearing levels by bone conduction. This measurement technique, which is not affected by middle ear infections, is the key diagnostic step. Moreover, in profoundly hearing loss children, it triggers reactions through vibratory stimulation and sets the scene for the conditioning of responses. Next, hearing levels are assessed by air conduction with the aid of headphones, in order to measure hearing levels in each ear as early as possible. A unique set-up is used to facilitate the emergence of reliable "surprise reactions", which may be interpreted by a sole examiner. Classical visual reinforcement is replaced by a highly interactive, dynamic and playful exchange between child and examiner, which gives meaning to the perception of stimuli and heralds the learning of hearing.

RESULTS

The results concern 105 babies suffering from bilateral sensorineural hearing loss and aged 4-18 months at the first behavioral test. Group 1 comprised 91 babies with no other handicap, in whom full bilateral air conduction was obtained in 82.4% before 12 months and in 98.9% before 18 months. In this group, air conduction in each ear was obtained in 47.0% before 12 months and in 70.3% before 18 months. In Group 2, which included 14 multiply handicapped babies, full bilateral air conduction was obtained in 37.5% before 12 months and in 78.6% before 18 months. Air conduction in both ears was obtained in 28.6% before 18 months.

CONCLUSION

The protocols described make it possible, in a minimum number of sessions, to measure hearing thresholds early over the whole range of hearing frequencies, even in multiply handicapped babies and those suffering from developmental retardation.