Phoneme boundaries in normal and hearing-impaired ears

Area of Science:

• Audiology
• Speech Perception
• Psychoacoustics

Background:

• Interpreting speech perception data from hearing-impaired listeners requires understanding complicating factors.
• Phoneme boundary data can be influenced by presentation level, ear of presentation, and individual hearing loss characteristics.

Purpose of the Study:

• To investigate variables that may complicate phoneme boundary data interpretation in hearing-impaired listeners.
• To differentiate the effects of audibility versus other distortions on speech perception in hearing impairment.

Main Methods:

• Two experiments were conducted using synthetic consonant-vowel syllables (/ba-da-ga/ continuum).
• Experiment 1 tested normal-hearing subjects across different presentation levels and ears.
• Experiment 2 tested unilaterally hearing-impaired listeners in their normal ear (unaided and spectrum-shaped) and impaired ear.

Main Results:

• Presentation level and ear of presentation had minimal impact on phoneme boundaries in normal-hearing listeners.
• Reduced audibility of acoustic/phonetic cues explained some, but not all, effects of hearing impairment on phoneme labeling.
• Other forms of distortion, beyond reduced audibility, affected labeling behavior in many hearing-impaired subjects.

Conclusions:

• Monaural presentation and high signal levels are unlikely to complicate phoneme boundary research with hearing-impaired listeners.
• Hearing impairment's impact on phoneme perception is complex, involving both reduced audibility and other signal distortions.
• Further research is needed to fully understand the perceptual consequences of hearing impairment.