Transcranial attenuation for bone conduction as a function of frequency (0.25 to 4 kHz.) was measured on a group of unilaterally deaf (n 15) and a group of normal (n = 35) ears. The results indicate a positive mean attenuation for all frequencies with a peak value of 13 db. for both groups at 2 kHz. Inter-subject variability was extremely large. This is considered to be a result of variability in skull bone thickness.

SUMMARY Hearing, speech, and language were studied in 26 children who survived severe perinatal asphyxia. The results of hearing tests showed that most children had a favourable outcome. Only 1 child had sensorineural deafness. Hearing loss in 6 others was due to middle-ear disease which resolved after treatment, and on retesting was found to be normal. The study also showed that neither gentamicin treatment nor incubator noise seemed to affect hearing. The results of speech and language assessment were less encouraging and about one-third of the children without serious mental or physical handicap had deficits in speech and language. It is suggested that the quality of life in such children could be improved if these deficits were detected early and adequately treated.

The problems associated with earmoulds currently used by hearing-impaired persons, particularly children, are outlined. A new type of earmould which combines high efficiency with minimal feedback is described and evaluated.

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This paper reports on a study set up to assess the corrosive behaviour of mercury and zinc air batteries in the gastric juice environment of the stomach. The results show a relatively rapid rate of corrosion for charged mercury batteries. In contrast, the zinc air battery showed no visible corrosion under the same conditions. In view of the toxic dangers from leakage of mercury batteries, it is recommended that steps be taken to ensure that such batteries do not remain in the acidic environment of the stomach, should ingestion occur.

Comparative properties have been determined for some commonly used ear impression materials (condensation reaction silicones) and some recently developed dental products (addition reaction silicones). Experiments have included measurement of dimensional stability, weight change on storage, viscosity, syringing characteristics, the energy required to tear the material and the stress relaxation characteristics. The major finding is that of the superb dimensional stability of the addition-cured silicones, which show no significant shrinkage over time. This is in contrast to a linear shrinkage of the order of 0.5% over a 48-hour period for the condensation silicones.

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