[Modification of speech encoding process of single channel cochlear implant utilizing digital delay circuit]

Area of Science:

• Audiology
• Biomedical Engineering
• Signal Processing

Context:

• Single-channel cochlear implants (SCIs) offer limited speech perception.
• Current encoding strategies do not fully leverage cochlear physiology.
• Improving auditory signal processing is crucial for SCI users.

Purpose:

• To investigate the impact of frequency-dependent delay coding on speech perception in SCI users.
• To determine optimal delay times for different vowel sounds based on cochlear tonotopy.
• To evaluate the efficacy of this novel encoding strategy compared to standard processing.

Summary:

• A novel encoding strategy was developed, applying digital delay to lower-frequency speech components while leaving higher-frequency components unprocessed.
• This approach is based on the physiological principle that high frequencies are perceived earlier than low frequencies in the cochlea.
• Two patients with SCIs (3M-House design) underwent testing without lip-reading, using a Sony SDP-777 ES surround processor for signal delay.
• Optimal delay times varied for different vowels, correlating with the first and second formant differences.
• Vowel identification scores improved significantly with the delay coding strategy: 30% vs. 16% in Case 1 and 48% vs. 30% in Case 2.

Impact:

• Demonstrates a potential method to enhance speech intelligibility for SCI recipients.
• Highlights the importance of considering cochlear tonotopy in auditory signal processing.
• Suggests that tailored signal delays can improve the perception of complex speech sounds like vowels.