Validity of diagnostic pure tone audiometry using a portable computerised audiometer without a sound-treated environment

Abstract

It is estimated that 10% of the global population is impaired to a significant degree by a decrease in hearing sensitivity. With the greatest proportion of these persons residing in developing countries where communities are grossly underserved, it is incumbent on hearing healthcare professionals to seek means of offering equitable hearing health care services to these communities. The delivery of conventional diagnostic hearing services to these population groups is challenged by limitations in human resources, financial constraints and by the dearth of audiometric testing facilities that are compliant with permissible ambient noise levels for reliable testing. Valid diagnostic hearing assessment without an audiometric test booth will allow greater mobility of services and could extend hearing healthcare service delivery in underserved areas. The purpose of this study was to investigate the validity of diagnostic pure tone audiometry in a natural environment, outside a sound treated room, using a computer-operated audiometer with insert earphones covered by circumaural earcups incorporating real-time monitoring of environmental noise. A within-subject repeated measures research design was employed to assess elderly adults with diagnostic air (250 to 8000 Hz) and bone (250 to 4000 Hz) conduction pure tone audiometry. The study was of a quantitative nature and the required data was collected by testing subjects initially in a natural environment and subsequently in a sound booth environment to compare the threshold measurements. One experienced audiologist used audiometric KUDUwave test equipment to evaluate subjects in both environments. A total of 147 adults with an average age of 76 (± 5.7) years were tested. Ears had pure tone averages (500, 1000, 2000 and 4000 Hz) of ≥ 25 dB in 59%, >40 dB in 23% and ˃ 55 dB in 6% of cases. Analysis of collected data showed air conduction thresholds (n = 2259) corresponding within 0 to 5 dB in 95% of all comparisons between testing in the natural and sound booth environments. Bone conduction thresholds (n = 1669) corresponded within 0 to 5 dB in 86% of comparisons and within 10 dB or less in 97% of cases. Average threshold differences (–0.6 to 1.1) and standard deviations (3.3 to 5.9) were within typical test-retest reliability limits. Recorded thresholds showed no statistically significant differences with a paired samples t-test (p ˃ 0.01) except at 8000 Hz in the left ear. Overall the correlation between the air-conduction thresholds recorded in the sound booth environment and the natural environment was very high (˃ 0.92) across all frequencies while for bone conduction threshold correlation for the two environments fell between 0.63 and 0.97. This study demonstrates that valid diagnostic pure tone audiometry in an elderly population can be performed in a natural environment using an audiometer employing insert earphones covered by circumaural earcups with real-time monitoring of ambient noise levels. Mobile diagnostic audiometry performed outside of an audiometric sound booth may extend current hearing healthcare services to remote underserved communities where booths are scarce or inaccessible. In combination with Telehealth applications this technology could offer a powerful and viable alternate diagnostic service to persons unable to attend conventional testing facilities for whatever reasons.