Richard E. White

Evaluation of a paired comparison elimination paradigm as a method of selecting hearing aids

Continuous discourse material with a background of interfering (“Cafeteria”) noise was processed by eight different hearing aids fitted to KEMAR. Tape recordings of the processed signals were then presented in pairs to individual listeners, whose judgements of relative intelligibility were used to eliminate competing aids and select an eventual winner. Discrimination scores were also obtained from each listener, using speech discrimination tests processed under identical conditions. In general, for each individual, there was a high correlation between the aid selected by paired comparisons and that selected by the highest discrimination score. Thus paired comparisons appeared to be a reliable means of identifying hearing aids yielding maximal speech discrimination scores. However, some aspects of the results raised questions about the nature of intelligibility judgments and whether different types of test material or different characteristics of the background noise might lead to different hearing aid sel...

On reducing auditory feedback in hearing aids

An inherent feature of a conventional magnetic earphone is that the diaphragm motion which generates acoustic output also gives rise to unbalanced displacing forces acting on the earphones case. Although the displacements of the case are small, the resulting acoustic radiation may be sufficient to cause feed back, particularly with high gain hearing aids. Following a suggestion by Mead Killion, an experimental dynamically balanced earphone system was constructed. Two conventional miniature earphones were coupled back‐to‐back so that their diaphragms always moved in opposite directions, thus reducing the net out‐of‐balance force on their cases. The acoustic outputs of the earphones were delivered to the hearing aid tubing via a simple manifold. The success of the scheme was confirmed both by the reduced vibration amplitude of the coupled cases and by a lower level of radiated sound. Preliminary results suggest that in the absence of other limitations this system could allow hearing aid gain to be increase...