Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Relationship between perception of spectral ripple and speech recognition in cochlear implant and vocoder listenersL.M. Litvak, A.J. Spahr, A.A. Saoji, and G.Y. FridmanL.M. Litvak, A.J. Spahr, A.A. Saoji, and G.Y. FridmanRelationship between perception of spectral ripple and speech recognition in cochlear implant and vocoder listenersFrequency (Hz)Cochlear Implant usersVariabilityWhy? Can we explain this variability by testing normal listeners?Where an explanation arise?Start from the beginning – the stimulation point.•Cochlear Implant: Auditory Nerve–Electric fields, overlap = distortion•Normal Listener: Basilar membrane–Auditory filters, spread = decreased spectral resolutionStimulation pointFrequency (Hz)Spectral LevelFrequency (Hz)Spectral LevelHow do we change the spectral resolution in normal listeners?Vocoder Simulations•Vocoder – electronic device that synthesizes speech•Vocoder Simulations–Reduces spectral information to 15 channels•Mimics CI processing–Drop-off varied 5 – 40 dB/octave•Mimics variable spectral resolutionHow do we measure the changes in normal listeners?Frequency (Hz)Perception of Spectral RippleHow well can we represent spectral information in speech?+ =Frequency (Hz)Spectral LevelSpectral modulation threshold•Spectral modulation threshold (SMT)–measure of spectral resolution–measures the spectral ripple perceptionWill the varied spectral resolution demonstrate the same variability seen in CI word recognition scores?L.M. Litvak, A.J. Spahr, A.A. Saoji, and G.Y. FridmanRelationship between perception of spectral ripple and speech recognition in cochlear implant and vocoder listenersMethods•25 CI users, 10 normal listeners•Normal listeners–Vocoder simulations•Speech–Separated in 15 bands–Multiplied by noise–Change rate of drop-off of noise spectrum»Varies spread•Tested for recognition of vowels and consonants •Compare word recognition scores Frequency (Hz)Results: VowelsResults: ConsonantsResults: ConsonantsPrimarily spectral cuesPrimarily Temporal / AmplitudeResults•Normal listeners–SMT increase = decrease in word recognition scores (WRS)–Decrease in WRS similar to CI listeners with similar SMTs•Variability in spread (due to SMT increase) of neural activity largely accounts for variability in CI users scores.Conclusions•Main Finding:–Same slope between CI and normal listeners•Spectral resolution = explanation of variability in CI users•Subsidiary Finding:–Differences between vowels and consonants•Temporal cuesQuestions•Additional Factors–Age of subjects•Alternative explanations–Other cues besides temporal cues–Frequency to place alignment problem•Central plasticityConfusion Matrix: VowelsConfusion Matrix:
View Full Document
Unlocking...