The effect of spatial separation of speech and noise sources on the optimal setting of the master hearing aid.

The sound fields in which hearing aid evaluations are performed with tests of speech discrimination are far from standardized. This investigation was concerned with the nature of the sound field in terms of separation of speech and noise sources as related to the optimal setting of a master hearing aid as indicated by listener performance scores on tests of speech discrimination in noise. Two sound fields were used in this investigation, one with speech and noise from the same source and another with speech and noise sources separated by 90 degrees and 45 degrees off the axis of the midsagittal plane of the listener. The repeatability of the optimal setting of the master hearing aid from one configuration to the other and the resolution available in each sound field, were of prime interest. The data indicated that the sound field configuration has no bearing on the optimal setting of the master hearing aid. The data did indicate that maximum resolution was available in the case of speech and noise from the same source.