Griffin, SK; (2017) Pitch perception in musical chords for cochlear implant users. Doctoral thesis , UCL (University College London).

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Abstract

Many people with severe or profound hearing loss are able to benefit from electronic hearing provided by a cochlear implant (CI); however, perception of music is often reported to be unsatisfactory. Due to the sound processing restrictions and current spread, CI users do not always perceive accurate pitch information, which adversely affects their ability to perceive and enjoy music. This thesis examines the factors affecting pitch perception in musical contexts for CI recipients. A questionnaire study was carried out in order to pilot and validate a questionnaire about music listening experience and enjoyment for bot pre- and post-lingually deafened CI users. Results of this study were generally more positive that previous questionnaire studies, especially from pre-lingually deafened CI users, but the majority of respondents were keen for an improvement to their music listening experience. CI users took part in a pilot study of the Chord Discrimination Test, identifying the “odd one out” of three different chord stimuli in which the difference was one semitone. The individual notes of the chords were presented either simultaneously or sequentially and spanned one to three octaves. Results showed significantly higher discrimination scores for simultaneously presented chords, possibly due to auditory memory difficulties for the sequential task.In the main study phase, participants undertook the tests with stimuli comprising both pure tones and simulated piano tones, and chord differences ranging from one to three semitones. No significant difference between the two tone conditions was found, but performance was significantly better when the difference between the chords was three semitones. A change in the top note of the chord was easier to detect than a change in the middle note. Peak performance occurred in the C5 octave range, which also correlated with scores on a consonant recognition test, suggesting a relationship between speech and music perception in this frequency area. Children took part in an abridged version of the Chord Discrimination Test. Children with normal hearing were able to identify a one semitone difference between musical chords, while hearing impaired children performaed at chance. Some children were also able to accurately identify a half semitone difference. NH children’s results showed an effect whereby performance fell when the notes of the chord remained within the C major scale, suggesting a potential for the Chord Discrimination Test to be used in assessments of sensitivity to musical scales. The Chord Discrimination Test was shown to be a versatile and adaptable tool with many potential applications for use in settings such as musical training, and pitch perception assessments in both research and clinical settings.

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