Haihong Feng

Musical Pitch Discrimination by Cochlear Implant Users

Objectives: The main goal of this study was to investigate the effects of acoustic characteristics, including timbre and fundamental frequency (F0), on the musical pitch discrimination of cochlear implant users. Methods: Eight postlingually deafened cochlear implant users were recruited, along with 8 control subjects with normal hearing. Pitch discrimination tests were carried out using test stimuli from 4 musical instruments plus synthetic complex stimuli. Three reference tones with different F0s were used. Results: The mean difference limens were 1.8 to 10.7 semitones in the just-noticeable difference task and 2.1 to 13.6 semitones in the pitch-direction discrimination task for different timbre and F0 combinations. Three-way analysis of variance showed that the acoustic characteristics of the musical stimuli, such as timbre and F0, significantly influenced pitch discrimination performance. Conclusions: Acoustic characteristics determine the complexity of the electrical stimulation pattern, which directly affects performance in pitch discrimination. A place pattern with a clear and regular low-order harmonic structure is most important for good pitch discrimination. A clear F0-related temporal pattern is also useful when the F0 is low. Pitch perception performance will worsen when there is interference in the high-frequency channels.

PCA based on mutual information for acoustic environment classification

Principal Component Analysis (PCA) is a common method for feature selection. In order to enhance the effect of selection, a Principal Component Analysis based on Mutual Information (PCAMI) algorithm is proposed. PCAMI introduces the category information, and uses the sum of mutual information matrix between features under different acoustic environments instead of covariance matrix. The eigenvectors of the matrix represent the transformation coefficients. The eigenvalues of the matrix are used to calculate the cumulative contribution rate to determine the number of dimension. The experiment on acoustic environment classification shows that PCAMI has better dimensionality reduction results and higher classification accuracy using neuron network than PCA.

Envelope pitch at different stimulation sites of cochlear implant

Pitch perception researches showed that temporal modulation plays an important role in pitch perception from unresolved harmonics. Fundamental frequency (F0) enhancement through temporal modulation of envelope was utilized in some cochlear implant (CI) signal processing strategies [e.g., Laneau, et.al., 2006] to improve the pitch perception of CI. In this study, Temporal Modulation Transfer Function (TMTF) and the relationship between Amplitude Modulation Rate (AMR) and pitch perception at different stimulation sites (apical, middle, and basal) were investigated. The stimuli are sinusoidal-amplitude–modulation pulse trains. Two psychophysical experiments were carried out: Two-Alternative-Forced Choice on modulated/un-modulated stimuli and AMR-Pitch Ranking. Experimental results showed that some of the CI subjects exhibited distinct performance at different stimulation sites, which implies that issues of stimulation sites and the subjects individual performance should be considered for F0 enhancement stra...

A novel F0 estimator for pitch enhancement in cochlear implant

Current experimental Cochlear Implant (CI) sound processing strategies like F0mod [Laneau, et.al., 2006], which aim to improve the pitch perception of CI subjects, amplitude-modulate the envelope of each frequency channel by the fundamental frequency (F0) of the speech sound. Due to the hardware limitation of CI devices, typical F0 estimation algorithms are too complex to be implemented. Low-complexity and accurate F0 estimator will be necessary for such manipulation. This study uses the Summary Auto-Correlation Function (SACF) to extract F0. The new pitch estimator was simulated and compared with typical algorithms that estimate F0 before the sub-band filtering. By the use of SACF, the new estimator reduces the computation load significantly and preserves good F0 estimation performance. # This work is supported by National Natural Science Foundation of China (11104316), and Shanghai Natural Science Foundation (11ZR1446000).

Relative contribution of temporal and spectral cues to melodic contour identification

The aim of this study was to investigate the relative contribution of temporal and spectral cues to melodic contour identification (MCI). Ten normal-hearing subjects participated in this study. Acoustic stimuli from four instruments and synthetic complex tone were utilized. A noise-excited vocoder was used to extract the temporal and spectral information from the stimuli. Experimental results showed that the spectral cue was more important to MCI than the temporal cue. Eight frequency bands were sufficient to achieve relatively good MCI performance. Temporal resolution showed no significant effect on the MCI performance. Confusion matrix was used to analysis the data. It was indicated that detecting pitch difference was easier than identifying pitch direction with restricted spectral information.

Temporal envelope and periodicity cues on musical pitch discrimination with acoustic simulation of cochlear implant

The present study investigated musical pitch discrimination with acoustic simulation of cochlear implant. A 4-channel noise-excited vocoder was used to simulate the signal processing of cochlear implants. Eight normal-hearing subjects participated in this study. Psychoacoustic experiments on pitch-direction discrimination test were carried out to examine the ability of detecting pitch-change direction. Stimuli from four instruments (clarinet, trumpet, piano and violin) were utilized. Experimental results showed that temporal envelope and periodicity information was important for musical pitch discrimination when the spectral information was limited.

Effects of frequency range, timbre and intonation on melodic contour identification with acoustic simulation of cochlear implant

The aim of this study was to determine how melodic contour identification with cochlear implant was affected by the frequency range, timbre and intonation. Noise-excited vocoder was used to simulate the signal processing for cochlear implant system. Melodic contour identification tests were carried out with eight normal-hearing subjects. Stimuli from four instruments (piano, trumpet, clarinet and violin) were utilized with different frequency ranges and intonations. Our experimental results showed that (i) temporal envelope information was important for melodic contour identification when the spectral information was limited; (ii) frequency range, timbre and intonation could influence melodic contour identification performance of the normal-hearing subjects when listening to the acoustic simulation of cochlear implant.