The Journal of the Acoustical Society of Korea (한국음향학회지)

The Acoustical Society of Korea (한국음향학회)
권호 표지

HRTF Interpolation Using a Spherical Head Model

원형 머리 모델을 이용한 머리 전달 함수의 보간

  • 이기승 (건국대학교 정보통신대학 전자공학부) ;
  • 이석필 (전자부품연구원 방송통신융합 연구센터)
  • Published : 2008.10.31
Download PDF
⟨ Previous Next ⟩

Abstract

In this paper, a new interpolation model for the head related transfer function (HRTF) was proposed. In the method herein, we assume that the impulse response of the HRTF for each azimuth angle is given by linear interpolation of the time-delayed neighboring impulse responses of HRTFs. The time delay of the HRTF for each azimuth angle is given by sum of the sound wave propagation time from the ears to the sound source, which can be estimated by using azimuth angle, the physical shape of the underlying head and the distance between the head and sound source, and the refinement time yielding the minimum mean square error. Moreover, in the proposed model, the interpolation intervals were not fixed but varied, which were determined by minimizing the total number of HRTFs while the synthesized signals have no perceptual difference from the original signals in terms of sound location. To validate the usefulness of the proposed interpolation model, the proposed model was applied to the several HRTFs that were obtained from one dummy-head and three human heads. We used the HRTFs that have 5 degree azimuth angle resolution at 0 degree elevation (horizontal plane). The experimental results showed that using only $30\sim40%$ of the original HRTFs were sufficient for producing the signals that have no audible differences from the original ones in terms of sound location.

본 논문에서는 머리 전달 함수에 대한 새로운 보간 기법을 제안하였다. 제안된 기법은 각 방위각에 대한 머리 전달 함수의 충격파 응답이 인접 방위각에 대한 시간 지연된 충격파 응답의 선형 보간으로 주어진다고 가정하였다. 각 방위각에 대한 충격파 응답의 시간 지연은 방위각, 머리의 물리적 형태, 음원과 머리의 거리 정보를 이용하여 추정될 수 있는 귀와 음원간의 전파시간과 최소 자승 오차를 갖도록 하는 교정값의 합으로 주어진다. 또한 제안된 모델에서는 보간 시 방위각의 간격을 고정 간격이 아닌 가변 간격으로 하였으며 본래 충격파 응답과 보간된 충격파 응답이 본래의 충격파 응답과 비교하여 청취 상으로 큰 차이가 느껴지지 않고, 보간에 필요한 충격파 응답의 재수가 최소화되는 조건을 만족하도록 결정하였다. 제안된 보간 모델의 유용성을 검증하기 위하여 더미 헤드 및 3명의 사람으로부터 측정된 머리 전달 함수에 대해 제안된 보간 모델을 적용하였다 머리 전달 함수는 0도의 고도각을 갖는 수평면을 5도 간격의 방위각으로 분할한 총 72개가 사용되었으며, 실험 결과 전체 머리 전달 함수 중 단지 $30\sim40%$ 만을 사용하고 나머지는 보간에 의해 얻어진 머리전달 함수를 사용하더라도 청취상의 음원의 위치가 변동되지 않음을 알 수 있었다.

Keywords

References

  1. P. F. Hoffmann and H. Moller, "Audibility of time differences in adjacent head-related transfer functions", Audio Engineering Society Preprint, 121st Convention, preprint no.6914, 2006
  2. D. Kistler and F. L. Wightman, "A model of head-related transfer functions based on principal components analysis and minimum-phase reconstruction", J. Acoust. Soc. Am., 91(3), 1637-1647, 1992 https://doi.org/10.1121/1.402444
  3. J. Breebaart and A. Kohlrausch, "The perceptual (ir) relevance of HRTF magnitude and phase spectra", Audio Engineering Society Preprint, 110th Convention, preprint no.5406, 2001
  4. A. Kulkarni, S. K. Isabelle and H. S. Colburn, "On the minimum-phase approximation of head-related transfer functions", Proceedings of IEEE ASSP workshop on applications of signal processing to audio and acoustics, 84-87, 1995
  5. P. Minnaar and J. Plogsties and F. Christensen, "Directional resolution of head-related transfer functions required in binaural synthesis", J. Audio Eng. Soc., 53(10), 919-929, 2005
  6. R. Tamura, Y. Hiraiwa, H. Hasegawa and M. Kasuga, "Research on the creation of a sound field using a 2-loudspeaker mobile phone", Proceedings of IEEE region 10 conference TENCON 2004, 120-123, 2004
  7. S. Hwang and Y. Park, "Time delay estimation from HRTFs and HRIRs", Proceedings of the 8th international conference on motion and vibration control (MOVIC 2006), 2006
  8. R. Nicol, V. Lemaire, A. Bondu and S. Busson, "Looking for a relevant similarity criterion for HRTF clustering: a comparative study", Audio Engineering Society Preprint, 120th Convention, preprint no. 6653, 2006
  9. S. Kim, S. Jang, D. Kong and S. Bang, "Adaptive virtual surround sound rendering method for an arbitrary listening position", Proceedings of AES 30th international conference, 2007
  10. R. O. Duda and W. L. Martens, "Range dependence of the response of a spherical head model", J. Acoust. Soc. Am., 104(5), 3048-3058, 1998 https://doi.org/10.1121/1.423886
  11. R. S. Woodworth and G. Schlosberg, Experimental Psychology, (Holt, Rinehard and Winston, New York, 349-361)
  12. A. Kulkarni, S. K. Isabelle and H. S. Colburn, "Sensitivity of human subjects to head-related transfer-function phase spectra", J. Acoust. Soc. Am., 105(5), 2821-2840, 1999 https://doi.org/10.1121/1.426898
  13. K.-S. Lee, "Temporal decomposition based on a ratedistortion criterion", IEEE Signal Processing Letters, 11(1), 33-35, 2004
  14. 이기승,"비트율-왜곡 기반 음성신호 시간축 분할", 한국음향학 회지, 21(3), 315-322, 2002
  15. D. D. Rife and J. Vanderkooy, "Transfer-Function Measurements using Maximum-Length Sequences", J. Audio Eng. Soc., 37(6), 419-444, 1989
  16. MIT media lab, KEMAR HRTF data, ftp://sound.media.mit.edu /pub/Data/KEMAR
  17. 황성목, 박영진, 박윤식, "Comparison of head-related transfer function models based on principle components analysis", 한국소음진동공학회논문집, 18(6), 642-653, 2008 https://doi.org/10.5050/KSNVN.2008.18.6.642
  18. S. Shimada, N. Hayashi and S. Hayashi, "A clustering method for sound localization transfer functions", J. Audio Eng. Soc., 42(7/8), 577-584, 1994
  19. F. Keyrouz and K. Diepold, "A new HRTF interpolation approach for fast synthesis of dynamic environmental interaction", J. Audio Eng. Soc., 56(1/2), 28-35, 2008