Children's speech recognition in noise using omni-directional and dual- microphone hearing aid technology

Objective: The purpose of this study was to examine children's speech recognition abilities for words and sentences presented in background noise when the children used omni-directional and dual-microphone hearing aid technology. Design: Twenty children (ten 4- to 6-yr olds; ten 7- to 11-yr- olds) with bilateral cochlear hearing loss (average four-frequency hearing loss = 57.25 dB HL; range: mild to severe) were included in the study. An adaptive test procedure was used to estimate a signal to noise ratio (SNR) that reduced individual speech recognition ability to 50% in multi-talker background competition. Testing was completed with the child seated in a conventional audiologic test suite. A fixed level of the speech signal was delivered through a loudspeaker located at 0°; noise varying in 2 dB steps was presented at 180°. SNR was estimated for two types of speech materials (closed-set words and sentences). Children wore binaural programmable hearing aids (Phonak PiCS) and were tested in conventional omni-directional and dual- microphone ('Audio Zoom') conditions. Results: Significant effects of microphone condition, speech material type (words and sentences), and age group ('younger' and 'older') were revealed by mixed design analysis of variance. Overall, children received a mean advantage of 4.7 dB from listening in the dual-microphone condition. Children's performance was correlated with their chronological age and language age (receptive vocabulary) but not with their degree of hearing loss (except in one condition). Younger children required a more advantageous SNR to achieve the same performance criteria as older children. Conclusions: Under the specific test conditions used in this investigation, dual-microphone hearing aid technology provided a significant listening advantage in background competition over conventional omni-directional microphones for children with mild to severe cochlear hearing loss for both word and sentence test materials.