1 / 18

Cassie Costilow

Human Frequency-Following Responses to Voice Pitch: Relative Contributions of the Fundamental Frequency and Its Harmonics. Cassie Costilow. Acknowledgements. Dr. Fuh-Cherng Jeng Dr. Chao-Yang Lee School of Hearing, Speech, and Language Sciences The Honors Tutorial College

amethyst-norton
Download Presentation

Cassie Costilow

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Human Frequency-Following Responses to Voice Pitch: Relative Contributions of the Fundamental Frequency and Its Harmonics Cassie Costilow

  2. Acknowledgements • Dr. Fuh-Cherng Jeng • Dr. Chao-Yang Lee • School of Hearing, Speech, and Language Sciences • The Honors Tutorial College • Graduate Audiology Students

  3. Introduction • The brain is capable of processing subtle changes in voice pitch, an ability necessary for understanding linguistic and emotional cues. • Speech sounds, like all complex sounds, contain a fundamental frequency (f0) and harmonics.

  4. The Phenomenon of the “Missing Fundamental Frequency” • While the f0 carries vital information of a complex sound, the pitch of the f0 can still be processed when it is removed from the stimulus. • Harmonics provide enough information for the brain to fill in the gap left by the missing f0. • However, the contribution of individual component frequencies of a complex sound have yet to examined.

  5. Temporal and Place Theories • Temporal Theory • Place Theory • Which one contributes more to pitch processing?

  6. Frequency Following Response • The frequency following response (FFR) is a scalp-recorded auditory evoked potential that follows the pitch contour of a complex stimulus. • Reflects neural phase-locking. • It is ideal for examining the “missing f0” because of its sensitivity to changes in voice pitch. • Provides physiological evidence of pitch processing in the human brainstem.

  7. Current Study • Purpose: examine the contribution of the f0 and each harmonic in pitch processing. • Hypotheses: • As frequency components are removed from the stimuli, FFR recordings will show a decreasing ability of the brain to process pitch information until no response can be recorded. • A slight response will still be present at the removal of the second harmonic. • A response will no longer be found after the removal of the 4th harmonic due to the fact that neural phase-locking decreases substantially for frequency components ≥ 1000 Hz. • A response will be seen when only the fundamental frequency is preserved.

  8. Methods: Participants • 17 total participants, data from only 12 was included in analysis. • 19-28 years (21.75 ± 2.89 years) • Normal hearing (20dB or better for octave frequencies between 125-8000 Hz) • Needed to be able to achieve a relaxed state. • Rejection rate of less than 10% necessary for all recorded trials. Failure of any one trial to meet this criteria resulted in all data for that participant being excluded.

  9. Methods: Auditory Stimulus • Monosyllabic Mandarin Chinese syllable representing the rising lexical tone yi2. • Conditions: • Intact • -f0 (high-pass filter cutoff of 170 Hz) • -h2 (340 Hz) • -h4 (680 Hz) • -h6 (1020 Hz) • -h8 (1360 Hz) • +f0 (low-pass filter cutoff of 170 Hz) • Duration of 250msec, rise and fall time of 10msec, silent interval of 45msec. • Presented monaurally through a ER-3A insert earphone at a intensity of 70 dB SPL. 2200 sweeps for each condition.

  10. Methods: Recording Procedures and Experimental Design • Participants were seated and reclined comfortable in an acoustically sound proof booth. • Stimuli presented monaurally to the right ear via an ER-3A insert earphone with a silent interval of 50ms • EEG recorded from three surface electrodes that were placed on the scalp • Recording montage: High Forehead (non-inverting), Right Mastoid (inverting), and Left Mastoid (ground) • Impedance maintained below 3kΩat 10 Hz

  11. Methods: Data Analysis • Offline analysis completed in MatLab and SigmaPlot • Four Objective Measures: • Frequency Error: Represents the accuracy of pitch tracking • Slope Error: Indicates how well the brain follows the overall shape of the pitch contour • Tracking Accuracy: Reflects accurateness of pitch encoding in the brainstem • Pitch Strength: Reflects robustness of the response • One-Way Repeated Measures ANOVA completed on four measures

  12. Results: Stimulus Spectrograms

  13. Results: Spectrograms of Typical Recording

  14. Results: Objective Measures

  15. Results: One-way ANOVA

  16. Discussion • Results demonstrated that both the fundamental frequency and harmonics contribute significantly to pitch processing. • The relative contributions of harmonics and temporal cues appear to be greater than the contributions of the f0 and place cues for pitch processing in the brainstem. • Possibilities: • Trade off between the choice of equalizing rms amplitude across acoustic tokens rather than maintaining the original amplitude of the f0 and each of its harmonics. • Sound intensity trade off in the –h6 condition.

  17. Discussion • Implications for the future: • Further investigation into the contributions of the fundamental frequency and its harmonics should be completed to see if language experience has an effect on the way pitch is processed. • Investigate the contribution of higher harmonics in pitch processing. • Temporal cues in speech processors.

  18. References • Aiken, S. J. & Picton, T. W. (2006). Envelope following responses to natural vowels. Audiology & Neuro-Otology, 11(4), 213-232. • Aiken, S. J. & Picton, T. W. (2008). Envelope and spectral frequency-following responses to vowel sounds. Hearing Research, 245, 35-47. • Ballantyne, D. (1990). Handbook of audiological techniques. Rushden: Butterworth-Heinemann. • Dajani, H. R., Purcell, D., Wong, W., Kunov, H., & Picton, T. W. (2005). Recording human evoked potentials that follow the pitch contour of a natural vowel. IEEE Transactions on Biomedical Engineering, 52(9) 1614-1518. • Krishnan, A. (2002). Human frequency-following responses: representation of steady-state synthetic vowels. Hearing Research, 166, 192-201. • Krishnan, A., Xu, Y., Gandour, J. T., & Cariani, P. A. (2004). Human frequency-following response: representation of pitch contours in Chinese tones. Hearing Research, 189, 1-12. • Krishnan, A. & Parkinson, J. (2000). Representation of Tonal Sweeps. Audiology & • Neuro-Otology, 5, 312-321. • Moushegian, G., Rupert, A. L., & Stillman, R. D. (1973). Scalp-recorded early responses in man to frequencies in the speech range. Electroencphalography and Clinical Nuerophysiology, 35(6), 665-667. • Young, E.D. & Sachs, M.B. (1979). Representation of steady-state vowels in the temporal aspects of the discharge patterns of populations of auditory-nerve fibers. Journal of the Acoustical Society of America, 66, 1381-1403. • Zatorre, R. J. (1988). Pitch perception of complex tones and human temporal-lobe function. Journal of the Acoustic Society of America, 84(2), 566-572.

More Related