All Issue

2021 Vol.40, Issue 6 Preview Page

Research Article

A method of wall absorption treatment for enhancing the speech intelligibility at a directional microphone array in a room

실내 공간 내 지향성 마이크 어레이에서의 음성 명료도 개선을 위한 벽면 흡음 처리 방법

Byeong-Yun Ko1
,
Jeong-Guon Ih1*
,
Wan-Ho Cho2
고 병윤1
,
이 정권1*
,
조 완호2
1한국과학기술원 기계공학과
2한국표준과학연구원
*Corresponding Author
30 November 2021. pp. 649-659
PDF XML Citation
Abstract

Wall absorption treatment effectively reduces reverberation, but requires a large area for a live room and each wall absorption affects speech intelligibility differently. In this study, we try to find the most effective wall for the absorption treatment using the beamforming array microphone in terms of speech intelligibility. The absorption importance factor is defined by using the collision number of reflected sounds on each wall. It allows estimating how much the speech signal will be enhanced by the absorption treatment. A cuboid room with a size of 107 m3 and a reverberation time of 1.1 s is selected for the simulation. When a Helmholtz-type absorption is treated on the wall with the most significant importance factor, the modified clarity for 500 and 1k Hz is improved by 5.1 dB and 4.8 dB respectively, and the speech transmission index is enhanced by 0.06. The difference in results between the proposed method and commercial simulation code is less than a Just-Noticeable Difference (JND). The absorption treatment on the wall with the most significant importance factor shows improvement greater than the wall with the largest area, and its difference is larger than a JND value.

Keywords
Speech intelligibility
Reverberation
Beamforming microphones
Absorption treatment
Room acoustic simulation

벽면 흡음 처리는 잔향의 제어에는 효과적이나, 잔향이 큰 공간의 경우에는 넓은 면적에 대한 적용이 필요하며, 각 벽면의 흡음은 음성 명료도에 다르게 영향을 미친다. 본 연구에서는 실내 음성 명료도의 관점에서 빔포밍 수음장치에 대한 잔향 제어를 위해 흡음 처리가 가장 효과적인 벽을 선택하는 모사 방법을 제안한다. 고정된 위치의 빔포밍 수음 어레이에 대해, 화자 혹은 스피커에서 방출된 음향이 각 벽면과 충돌하는 변수를 이용해 벽면 중요도 계수를 정의하고, 이를 이용해 흡음 처리에 따른 수음부의 음성개선 효과를 예측하는 방법을 제시했다. 검증을 위해 체적이 107 m3, 잔향시간이 1.1 s인 직육면체형 실내공간에 대해 모사 실험을 진행했다. 중요도 계수가 가장 높은 벽면에 헬름홀츠 흡음기를 적용할 때 수정된 음성 명료도는 500 Hz, 1 kHz에서 각각 5.1 dB와 4.8 dB, 또 음성전달 지수는 0.06만큼의 향상이 예측되었는데, 이는 상용코드의 계산 결과와 차이인지 역치(Just-Noticeable Difference, JND) 이내의 차이로 일치했다. 분석결과, 벽면 중요도가 가장 높은 곳에 흡음 처리한 결과는 면적이 가장 넓은 천장에 같은 흡음률을 적용할 때보다 음성 명료도 지수가 JND 이상으로 더 개선되는 것을 알 수 있었다.

키워드
음성 명료도
잔향
빔포밍 마이크
흡음 처리
실내음향 모사
References
1
H. Kuttruff, Room Acoustics (CRC Press, Florida, 2016), Chaps. 4-5. 10.1201/9781315372150
2
M. Brandstein, Microphone Arrays: Signal Processing Techniques and Applications (Springer, Berlin, 2001), Chaps. 1-2. 10.1007/978-3-662-04619-7
3
M. Kleiner and J. Tichy, Acoustics of Small Rooms (CRC Press, Florida, 2014), Chaps. 1-4. 10.1201/b16866
4
J. Benesty, S. Makino, and J. Chen, Speech Enhancement (Signals and Communication Technology) (Springer, Berlin, 2005), Chaps. 1, 11.
5
O. Thiergart, G. Del Galdo, and E. A. Habets, "On the spatial coherence in mixed sound fields and its application to signal-to-diffuse ratio estimation," J. Acoust. Soc. Am. 132, 2337-2346 (2012). 10.1121/1.475049323039430
6
A. Schwarz and W. Kellermann, "Coherent-to-diffuse power ratio estimation for dereverberation," IEEE/ ACM Trans. on Audio, Speech, and Lang. Process. 23, 1006-1018 (2015). 10.1109/TASLP.2015.2418571
7
L. L. Beranek and T. Mellow, Acoustics: Sound Fields and Transducers (Academic Press, London, 2012), Chap. 10.
8
R. H. Bolt, "Note on normal frequency statistics for rectangular rooms," J. Acoust. Soc. Am. 18, 130-133 (1946). 10.1121/1.1916349
9
A. K. Nábèlek and L. Robinette, "Influence of the precedence effect on word identification by normally hearing and hearing‐impaired subjects," J. Acoust. Soc. Am. 63, 187-194 (1978). 10.1121/1.381711632410
10
ANSI S3.5-1997, Methods for Calculation of the Speech Intelligibility Index, 1997.
11
IEC 60268-16, Sound System Equipment-Part 16: Objective Rating of Speech Intelligibility by Speech Transmission Index, ed. 4,. 2011.
12
C. H. Jeong, J. G. Ih, and J. H. Rindel, "An approximate treatment of reflection coefficient in the phased beam tracing method for the simulation of enclosed sound fields at medium frequencies," Applied Acoustics, 69, 601-613, (2008). 10.1016/j.apacoust.2007.02.002
13
ISO 354: 2003, Acoustics--Measurement of Sound Absorption in a Reverberation Room, 2003.
14
J. B. Allen and D. A. Berkley, "Image method for efficiently simulating small‐room acoustics," J. Acoust. Soc. Am. 65, 943-950 (1979). 10.1121/1.382599
15
ISO 3382-1: 2009, Acoustics--Measurement of Room Acoustic Parameters-Part 1:Prformance Spaces, 2009.
16
C. L. Christensen, "Odeon room acoustics program," v. 13.0., User Manual, 2013.
17
T. J. Cox and P. D'antonio, Acoustic Absorbers and Diffusers: Theory, Design and Application (CRC Press, London, 2009), Chap. 7.
18
J. H. Rindel, "Computer simulation techniques for acoustical design of rooms," Acoustics Australia 23, 81-86 (1995).
19
J. S. Bradley, R. Reich, and S. G. Norcross, "A just noticeable difference in C50 for speech," Applied Acoustics, 58, 99-108 (1999). 10.1016/S0003-682X(98)00075-9
Information
  • Publisher :The Acoustical Society of Korea
  • Publisher(Ko) :한국음향학회
  • Journal Title :The Journal of the Acoustical Society of Korea
  • Journal Title(Ko) :한국음향학회지
  • Volume : 40
  • No :6
  • Pages :649-659
  • Received Date : 2021-09-23
  • Revised Date : 2021-11-01
  • Accepted Date : 2021-11-15
  • DOI :https://doi.org/10.7776/ASK.2021.40.6.649
Journal Informaiton The Journal of the Acoustical Society of Korea The Journal of the Acoustical Society of Korea
E-Book
  • scopus_JASK
  • ESCI_JASK
  • Google scholar_JASK
  • NRF
  • KOFST
  • KISTI Current Status
  • KISTI Cited-by
  • crosscheck
  • orcid
  • ccl
Journal Informaiton Journal Informaiton - close