The purpose of the laboratory tests of the current investigation was to examine how visual cues impact directional (DIR) benefit and preference for the DIR microphone hearing aid (re: the omnidirectional [OMNI] microphone). Specifically, three hypotheses were examined: (1) the presence of visual cues would improve OMNI-aided performance to ceiling levels and therefore reduce DIR benefit and preference, (2) DIR benefit measured in the audiovisual (AV) condition could not be predicted by that measured using auditory-only (AO) testing, and (3) with visual cues, listeners with greater lipreading skills would perceive less DIR benefit than did listeners with lesser lipreading skills.
Twenty-four adults with sensorineural hearing loss were recruited. Their speech recognition performances were measured in two hearing aid microphone modes (DIR and OMNI), at various signal-to-noise ratios (SNR, −10 to +10 dB in 4-dB steps) and under two presentation conditions (AV and AO) by using the AV version of the Connected Speech Test. Microphone preference (DIR versus OMNI) was also assessed with and without visual cues at each of the SNRs by using the same Connected Speech Test sentences. Lipreading skills were measured using the Utley test.
The speech recognition data revealed that the participants obtained significantly less DIR benefit in the AV condition because their AV performances were at the ceiling level. Consistent with this, the likelihood of preferring DIR processing was significantly reduced when visual cues were available to the listeners. Further, DIR benefit measured in the AV condition was not correlated with that measured in the AO condition while being significantly and negatively correlated with lipreading skill.
These results suggest that AO laboratory testing overestimates the DIR benefit and preference for DIR processing that hearing aid users may have in most face-to-face conversations in typical SNR, real-world environments. Additionally, because the DIR benefit measured in the AV condition cannot be predicted by the benefit score obtained from traditional AO laboratory testing, the effect of visual cues should be considered in establishing a valid laboratory/clinical environment and protocol for DIR microphone hearing aid testing. In light of these findings, consultations should be provided for hearing aid users with superior lipreading skills to help them adjust their expectations regarding the possibly small perceivable benefit gained from DIR microphone hearing aids.
The benefits provided by directional (DIR) microphone hearing aids have been found to vary between results observed in the laboratory and those obtained in the real world. In this study, 24 participants compared microphone success with and without concomitant use of visual cues to determine whether visual cues could explain this laboratory-field discrepancy. The laboratory results indicated that, when visual cues were available, the DIR benefit was reduced and DIR processing was less often preferred, especially by listeners with superior lipreading skills. Furthermore, DIR benefit measured when accompanied by visual cues could not be predicted by that measured in the absence of visual cues. These results suggest the importance of incorporating visual cues in the evaluation of DIR microphone effectiveness.
Department of Communication Sciences and Disorders, The University of Iowa, Iowa City, Iowa.
Address for correspondence: Yu-Hsiang Wu, Department of Communication Sciences and Disorders, The University of Iowa, 119 WJSHC, Iowa City, IA 52242. E-mail: email@example.com.
Received May 29, 2008; accepted July 29, 2009.