Consonant and Vowel Confusions in Well-Performing Children and Adolescents With Cochlear Implants, Measured by a Nonsense Syllable Repetition Test

Abstract

Although the majority of early implanted, profoundly deaf children with cochlear implants (CIs), will develop correct pronunciation if they receive adequate oral language stimulation, many of them have difficulties with perceiving minute details of speech. The main aim of this study is to measure the confusion of consonants and vowels in well-performing children and adolescents with CIs. The study also aims to investigate how age at onset of severe to profound deafness influences perception. The participants are 36 children and adolescents with CIs (18 girls), with a mean ( SD ) age of 11.6 (3.0) years (range: 5.9–16.0 years). Twenty-nine of them are prelingually deaf and seven are postlingually deaf. Two reference groups of normal-hearing (NH) 6- and 13-year-olds are included. Consonant and vowel perception is measured by repetition of 16 bisyllabic vowel-consonant-vowel nonsense words and nine monosyllabic consonant-vowel-consonant nonsense words in an open-set design. For the participants with CIs, consonants were mostly confused with consonants with the same voicing and manner, and the mean ( SD ) voiced consonant repetition score, 63.9 (10.6)%, was considerably lower than the mean ( SD ) unvoiced consonant score, 76.9 (9.3)%. There was a devoicing bias for the stops; unvoiced stops were confused with other unvoiced stops and not with voiced stops, and voiced stops were confused with both unvoiced stops and other voiced stops. The mean ( SD ) vowel repetition score was 85.2 (10.6)% and there was a bias in the confusions of [i:] and [y:]; [y:] was perceived as [i:] twice as often as [y:] was repeated correctly. Subgroup analyses showed no statistically significant differences between the consonant scores for pre- and postlingually deaf participants. For the NH participants, the consonant repetition scores were substantially higher and the difference between voiced and unvoiced consonant repetition scores considerably lower than for the participants with CIs. The participants with CIs obtained scores close to ceiling on vowels and real-word monosyllables, but their perception was substantially lower for voiced consonants. This may partly be related to limitations in the CI technology for the transmission of low-frequency sounds, such as insertion depth of the electrode and ability to convey temporal information.

Listening effort is not the same as speech intelligibility score

“…The second type of distortion was an intentional mispronunciation of the first consonant in the target word. This mispronunciation nearly always was a change in the place of articulation of the consonant, which is the feature most often misperceived by listeners with hearing loss (Walden & Montgomery 1975;Dubno et al 1982), including those who wear CIs (Munson et al 2003;Rødvik et al 2019). The mispronunciations were intended to be non-words, but (out of 120) of the mispronunciations produced real English words.…”

Evaluation of working memory in relation to cochlear implant consonant speech discrimination

“…In postlingually deaf adults, the neural pathways in the brain have been shaped by acoustic sound perception before onset of deafness. The degree of success with a CI depends on how the brain compares the new signal with what was heard previously [27].…”

Visualization of Speech Perception Analysis via Phoneme Alignment: A Pilot Study

“…First, confusion matrices for the consonants and vowels were generated. Each matrix consisted of N rows of phonemes in the stimulus set and N + 1 columns of phonemes in the response set with the extra column reserved for unclassified phonemes due to empty responses ( 40 , 42 ). The matrices were regenerated as several smaller ones based on the prescribed phonological features.…”

“…Second is the entropy or uncertainty for each of the 39 phonemes obtained from the two confusion matrices for the consonants and the vowels used for the phonemegram. Similar to above, the entropy is calculated as where k sums over all the response phonemes as well as unclassified ones due to empty responses ( 40 , 42 ). Third is the information transfer for the same ten phonological features used in the phonemegram.…”