Simulated bimodal speech perception in noise for native and non-native speech
Creators: name: Xu, Can (Ph. D. In Communication Sciences And Disorders)
name: 0000-0001-8441-8663
Publisher: name: The University of Texas at Austin
Year: 2023
Subjects: Cochlear implants
Hearing aids
Bimodal benefits
Non-native speech perception

description: Approximately 70%-72% of cochlear implant recipients have aidable residual low-frequency hearing in their non-implanted ears. Bimodal hearing by using a hearing aid in the non-implanted ear provides benefits for these patients in multiple auditory domains, including speech perception in quiet and noise, sound localization, and music perception and appreciation. This bimodal benefit has also been observed in simulated bimodal hearing using a vocoded signal and a lowpass filtered signal contralaterally. Previous findings suggested the importance of providing binaural hearing, low-frequency temporal fine structures, and glimpsing in low frequencies in bimodal benefits, particularly in noise. The majority of the previous studies have been investigating bimodal benefits in monolinguals. The lack of understanding of bimodal benefits in bilinguals result in less agreement regarding the best clinical guidelines for providing services for bilingual bimodal patients. The present study thus focused on Mandarin native speakers’ bimodal speech perception in quiet and noise in their native language (Mandarin) and non-native language (English). This study used a simulated bimodal speech in Mandarin and English with vocoded speech in the right ear and three different bimodal processes in the left ear. Various noise conditions were also investigated, including different signal-to-noise ratios (-3 dB and -6 dB) and temporal modulation in noise (steady-state speech-shaped noise and temporally modulated noise at 16 Hz). Results in this study suggested that bimodal benefits were only observed in noise but not in quiet. This is probably due to the ceiling effect in speech recognition in quiet and limited linguistic and contextual information contained in the speech materials used in the current study. Participants may have achieved high performance in quiet, relatively easy listening conditions, mainly when they have normal hearing. Investigation of bimodal benefits in two languages indicated higher bimodal benefits in noise for Mandarin than for English. The results may be related to the intrinsic native advantage in speech perception, and the native advantage was also applied to bimodal hearing. The provision of low-frequency fundamental frequency information by acoustic stimulation may contribute to Mandarin lexical tone recognition too, and thus enhanced bimodal benefits in Mandarin. Surprisingly, modulation frequency did not significantly affect bimodal benefits in noise, possibly because bimodal benefits depend on temporal fine structures in noise but not the envelope in noise contained in both steady-state noise and temporally modulated noise. Moreover, a positive correlation was found between English bimodal benefit in noise and the length of living experience in the U.S. Overall, bimodal benefits were observed in bilingual speakers’ native and non-native languages, which may indicate a need for clinical support in native and second languages for bilingual bimodal patients.