Journal of the Institute of Electronics Engineers of Korea SC (전자공학회논문지SC)

The Institute of Electronics and Information Engineers (대한전자공학회)
권호 표지

A Study of Acoustic Masking Effect from Formant Enhancement in Digital Hearing Aid

디지털 보청기에서의 포먼트 강조에 의한 마스킹 효과 연구

  • Jeon, Yu-Yong (Electronic Engineering, Inha University) ;
  • Kil, Se-Kee (Institute for Information and Electronics Research) ;
  • Yoon, Kwang-Sub (Department of Electrical and Computer Engineering, Inha University) ;
  • Lee, Sang-Min (Department of Electrical and Computer Engineering, Inha University)
  • 전유용 (인하대학교 전자공학과) ;
  • 길세기 (인하대학교 전자공학과 정보전자공동연구소) ;
  • 윤광섭 (인하대학교 전자공학부 정보전자공동연구소) ;
  • 이상민 (인하대학교 전자공학부 정보전자공동연구소)
  • Published : 2008.09.25
Download PDF
⟨ Previous Next ⟩

Abstract

Although digital hearing aid algorithms have been developed to compensate hearing loss and to help hearing impaired people to communicate with others, digital hearing aid user still complain about difficulty of hearing the speech. The reason could be the quality of speech through digital hearing aid is insufficient to understand the speech caused by feedback, residual noise and etc. And another thing is masking effect among formants that makes sound quality low. In this study, we measured the masking characteristics of normal listeners and hearing impaired listeners having presbyacusis to confirm masking effect in speech itself. The experiment is composed of 5 tests; pure tone test, speech reception threshold (SRT) test, word recognition score (WRS) test, puretone masking test and speech masking test. In speech masking test, there are 25 speeches in each speech set. And log likelihood ratio (LLR) is introduced to evaluate the distortion of each speech objectively. As a result, the speech perception became lower by increasing the quantity of formant enhancement. And each enhanced speech in a speech set has statistically similar LLR, however speech perception is not. It means that acoustic masking effect rather than distortion influences speech perception. In actuality, according to the result of frequency analysis of the speech that people can not answer correctly, level difference between first formant and second formant is about 35dB, and it is similar to result of pure tone masking test(normal hearing subject:36.36dB, hearing impaired subject:32.86dB). Characteristics of masking effect is not similar between normal listeners and hearing impaired listeners. So it is required to check the characteristics of masking effect before wearing a hearing aid and to apply this characteristics to fitting.

청력 손실을 보상하고 난청인이 다른 사람들과 대화할 수 있도록 디지털 보청기 알고리즘은 개발 되어 왔음에도 불구하고, 디지털 보청기 사용자들은 음성을 듣는데 어려움이 있다고 불만을 토로한다. 그 이유는 피드백이나 잔여 노이즈 등에 의해 디지털 보청기를 통한 음성의 질이 이해하기에 불충분하기 때문이다. 또 다른 이유로 포먼트들 사이에서 일어나는 마스킹 현상이 될 수 있다. 이 연구에서 정상 청각 피험자와 노인성 난청을 갖고 있는 난청인 피험자의 마스킹 특성을 측정하여 음성에서의 마스킹에 의한 음성 인지 저하를 확인하기 위한 실험을 하였다. 실험은 순음검사, 어음 청취 역치 검사, 낱말 분별력 검사, 수음 마스킹 검사, 어음 마스킹 검사의 5개 테스트로 이루어졌다. 어음 마스킹 검사에서 각각 어음 세트에 25개의 어음이 사용되었다. 각 어음의 왜곡을 객관적으로 평가하기 위해서 log likelihood ratio (LLR)를 도입하였다. 결과적으로 포먼트 향상의 양을 늘리면 늘릴수록 어음 인지는 낮아졌고, 각 어음 세트에서 각각의 향상된 어음은 통계적으로 비슷한 LLR을 갖지만 어음인지는 그렇지 않게 나타났다. 이것은 왜곡이 아닌 음향 마스킹이 어음 인지에 영향을 준다는 것을 의미한다. 실제로 피험자들 대부분이 맞추지 못한 음성을 주파수 분석한 결과 첫 번째와 두 번째 포먼트 사이의 레벨 차이가 약 35dB이며 이는 순음 마스킹 실험 결과(정상 청각 피험자:36.36dB, 난청인 피험자:32.86dB)와 비슷한 양상을 보였다. 실험 결과에서 볼 수 있듯이 음향 마스킹의 특성은 정상 청각인과 난청인 사이에서 다르게 나타난다. 그렇기 때문에 보청기 착용 전 마스킹 특성을 검사하고, 피팅 시에 적용해야 한다.

Keywords

References

  1. Danaher, E. M., and Pickett, 1. M., "Some masking effects produced by low-frequency vowel formants in persons with sensorineural hearing loss," J. Speech Hear. Res., 18, pp. 261-271, 1975 https://doi.org/10.1044/jshr.1802.261
  2. Irwin Pollack , "Auditory informational masking", The Journal of the Acoustical Society of America, Volume 57, IssueS1, p.S5, April 1975
  3. James P. Egan and Haerold W. Hake, "On the Masking Pattern of a Simple Auditory Stimulus", The Journal of the Acoustical Society of America, Vol.22, no.5, pp.622-630, September 1950 https://doi.org/10.1121/1.1906661
  4. Richard H. Ehmer, "Masking Patterns of Tones", The Journal of the Acoustical Society of America, Vol.31, no.8, August 1959
  5. Hartley D. E. H., Wright B. A. and Moore D.R., "Age-Related Improvements in Auditory Backward and Simultaneous Masking in 6- to 10 -Year-Old Children," Journal of Speech, Language, and Hearing Research, Vol.43, pp.2-1415, December 2000
  6. Dubno, Judy R, Ahlstrom, Jayne B, "Psychophysical suppression effects for tonal and speech signals," The Journal of the Acoustical Society of America, Vol.110, Issue 4, pp.2108 -2119, October 2001 https://doi.org/10.1121/1.1403699
  7. Hans A. Gustafsson and Stig D. Arlinger, "Masking of speech by amplitude-modulated noise," The Journal of the Acoustical Society of America, Vol.95, Issue 1, pp518-529, January 1994 https://doi.org/10.1121/1.408346
  8. Van Summers Michelle R. Molis, "Speech Recognition in Fluctuating and Continuous Maskers," Journal of Speech, Language, and Hearing Research, Vol.47, pp245-256, April 2004 https://doi.org/10.1044/1092-4388(2004/020)
  9. Alcantara J.I., Moore B.C.J., "The relative role of beats and combination tones in determining the shapes of masking patterns," Hearing Research, Vol.165, Number 1, pp103-116, March 2002 https://doi.org/10.1016/S0378-5955(02)00291-5
  10. Ifat Yasin and Christopher J. Plack, "The Role of Suppression in the Upward Spread of Masking," Journal of the Association for Research in Otolaryngology, Vol. 6, Number 4, pp368-377, December 2005 https://doi.org/10.1007/s10162-005-0014-7
  11. J. Thiemann, "Acoustic Noise Suppression for Speech Signals using Auditory Masking Effects," M.S. thesis McGill University, Montreal, Canada, May 2001
  12. Viraq, N., "Single Channel Speech Enhancement Based on Masking Properties of the Human Auditory System," Speech and Audio Processing, IEEE Transactions on, Vol. 7, Issue 2, pp126 -137, Mar 1999 https://doi.org/10.1109/89.748118
  13. Hesu Huang Kyriakakis, C., "Binaural Noise Reduction Combining Binaural Analysis and Psychoacoustically Motivated Spectral Subtraction," Signals, Systems and Computers, 2004. Conference Record of the Thirty-Eighth Asilomar Conference on, IEEE, Vol. 2, pp2260 -2264, Nov. 2004
  14. Quackenbush, S.R., Barnwell, T.P., Clements, M.A., "Objective Measures of Speech Quality", Prentice-Hall,NJ, pp.47-51, 1988
  15. H. Timothy Bunnell, "On Enhancement of spectral contrast in speech for hearing impaired listeners", The Journal of the Acoustical Society of America. 88(6). December 1990