Impact of visual cues on directional benefit and preference: Part II--field tests

The field tests performed in the current investigation examined how visual cues impact the benefit provided by directional (DIR) microphone hearing aids in the real world. Specifically, the study tested the hypotheses that (1) the provision of visual cues would reduce the preference for DIR processing (re: omnidirectional [OMNI] microphone) and (2) laboratory audiovisual (AV) testing would predict real-world outcomes better than auditory-only testing.

The same 24 hearing-impaired adults enrolled in the laboratory testing of this study compared microphone modes (DIR versus OMNI processing) in their everyday activities three times a day for 4 wk using paper and pencil journals. In each comparison, the participants were asked to identify an environment that favored DIR processing (e.g., the talker standing in front of the user and noise at his or her back), listen to speech amid noise via both the DIR and OMNI microphone modes, and then record the preferred microphone mode in the journal. To further understand what the listeners based their preference on, the participants were also asked to provide the reasons for their preferences. Microphone modes were compared when the listeners' eyes were either open or closed.

The field results first suggested that OMNI processing was more frequently preferred over DIR processing. Visual cues were not found to have a significant effect on preference for DIR processing. Furthermore, the analysis revealed that when listeners indicated "louder" or "less internal noise" as the reasons for their microphone preference, the likelihood of preferring the OMNI mode increased significantly, suggesting that OMNI processing was preferred for its louder output and lower internal circuit noise level. Finally, the preference score obtained by the laboratory preference judgment task under the AV condition was shown to be the best predictor of microphone preference in the real world.

The field data did not reveal the effect of visual cues on preference for DIR processing because preference was not altered by the availability of visual cues. This negative result may be due to the unsuccessful control of visual cues during the field trial. However, the finding that AV laboratory testing predicted field outcomes more accurately than did auditory-only testing demonstrates the role of visual cues in the real world and emphasizes the necessity of using AV testing in the laboratory to evaluate DIR microphone hearing aids. Furthermore, this study demonstrates the importance of factors other than DIR benefit-such as loudness and hearing aid internal noise-in determining preference for microphone mode in the real world.