Effects of amplification and speechreading on consonant recognition by persons with impaired hearing

Objective: This study sought to describe the consonant information provided by amplification and by speechreading, and the extent to which such information might be complementary when a hearing aid user can see the talker's face. Design: Participants were 25 adults with acquired sensorineural hearing losses who wore the GN Re-Sound BT2 Personal Hearing System binaurally. Consonant recognition was assessed under four test conditions, each presented at an input level of 50 dB SPL: unaided listening without speechreading (baseline), aided listening without speechreading, unaided listening with speechreading, and aided listening with speechreading. Confusion matrices were generated for each of the four conditions to determine overall percent correct for each of 14 consonants, and information transmitted for place of articulation, manner of articulation, and voicing features. Results: Both amplification and speechreading provided a significant improvement in consonant recognition from the baseline condition. Speechreading provided primarily place-of-articulation information, whereas amplification provided information about place and manner of articulation, as well as some voicing information. Conclusions: Both amplification and speechreading provided place-of-articulation cues. The manner-of-articulation and voicing cues provided by amplification, therefore, were generally complementary to speechreading. It appears that the synergistic effect of combining the two sources of information can be optimized by amplification parameters that provide good audibility in the low-to-mid frequencies.