Enhancement of Electrolaryngeal Speech by Adaptive Filtering Artificial larynges provide a means of verbal communication for people who have either lost or are otherwise unable to use their larynges. Although they enable adequate communication, the resulting speech has an unnatural quality and is significantly less intelligible than normal speech. One of the major problems with the widely ... Research Article
Research Article  |   December 01, 1998
Enhancement of Electrolaryngeal Speech by Adaptive Filtering
 
Author Affiliations & Notes
  • Carol Y. Espy-Wilson
    Boston University Boston, MA
  • Venkatesh R. Chari
    Boston University Boston, MA
  • Joel M. MacAuslan
    Speech Technology and Applied Research Corp. Lexington, MA
  • Caroline B. Huang
    Boston University Boston, MA
  • Michael J. Walsh
    Veterans Administration Medical Center Boston, MA
  • Contact author: Carol Y. Espy-Wilson, PhD, Department of Electrical and Computer Engineering, Boston University, 8 St. Mary’s Street, Boston, MA 02215-2421. Email: espy@bu.edu
Article Information
Speech, Voice & Prosodic Disorders / Voice Disorders / Hearing & Speech Perception / Acoustics / Speech, Voice & Prosody / Speech / Research Articles
Research Article   |   December 01, 1998
Enhancement of Electrolaryngeal Speech by Adaptive Filtering
Journal of Speech, Language, and Hearing Research, December 1998, Vol. 41, 1253-1264. doi:10.1044/jslhr.4106.1253
History: Received February 27, 1998 , Accepted June 16, 1998
 
Journal of Speech, Language, and Hearing Research, December 1998, Vol. 41, 1253-1264. doi:10.1044/jslhr.4106.1253
History: Received February 27, 1998; Accepted June 16, 1998

Artificial larynges provide a means of verbal communication for people who have either lost or are otherwise unable to use their larynges. Although they enable adequate communication, the resulting speech has an unnatural quality and is significantly less intelligible than normal speech. One of the major problems with the widely used Transcutaneous Artificial Larynx (TAL) is the presence of a steady background noise caused by the leakage of acoustic energy from the TAL, its interface with the neck, and the surrounding neck tissue. The severity of the problem varies from speaker to speaker, partly depending upon the characteristics of the individual's neck tissue. The present study tests the hypothesis that TAL speech is enhanced in quality (as assessed through listener preference judgments) and intelligibility by removal of the inherent, directly radiated background signal. In particular, the focus is on the improvement of speech over the telephone or through some other electronic communication medium. A novel adaptive filtering architecture was designed and implemented to remove the background noise. Perceptual tests were conducted to assess speech, from two individuals with a laryngectomy and two normal speakers using the Servox TAL, before and after processing by the adaptive filter. A spectral analysis of the adaptively filtered TAL speech revealed a significant reduction in the amount of background source radiation yet preserved the acoustic characteristics of the vocal output. Results from the perceptual tests indicate a clear preference for the processed speech. In general, there was no significant improvement or degradation in intelligibility. However, the processing did improve the intelligibility of word-initial non-nasal consonants.

Acknowledgments
This study was supported by NIH grant 1R43-DC02925-01 and a Clare Booth Luce Fellowship to the first author. A preliminary report of the results of this study appeared in the Proceedings of the International Conference on Spoken Language Processing (pp. 764–767), published by the Alfred I. Dupont Institute of the University of Delaware (1996). Newcastle, DE: Citation Delaware. We wish to acknowledge the cooperation of the Speech Pathology Laboratory of the Boston Veterans’ Administration Medical Center in permitting us the use of their recording room, as well as providing assistance in contacting the laryngectomized speakers. Thanks also to Deborah Schwartz for her help in recording and digitization. Finally, we would like to thank the anonymous reviewers for their helpful comments on an earlier version of the paper.
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