Hearing defects of noise trauma type with lack of noise exposure.

Screening audiometry in children not infrequently reveals a 4 kHz dip. Evidence for noise trauma as the etiological background of this 4 kHz dip have been presented in the literature. Thirty children with hearing defects of this characteristic type and no history of noise exposure were studied. Their mean age was 14 years and the average observation time 4.2 years. Slight progression of hearing impairment (greater than 15 dB at two frequencies) was noted in 3 children (10%). A history of hearing defects in the family was found in 76%, as against 17% in a control group. Abnormal elevation of stapedius reflex thresholds was observed in 83% of the material. It is concluded that in children with a 4 kHz dip and no history of significant exposure to noise, genetic disposition is the predominant etiological element underlying the hearing defect. There was no indication of increased sensitivity to general noise exposure, but as always in sensorineural high frequency hearing loss avoidance of significant exposure to noise is to be recommended.