Beamforming and maximum likelihood estimation for speech enhancement using dual closely-spaced microphones
GONG Qin1,2, ZHENG Shuo1
1. Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China; 2. Research Center of Biomedical Engineering, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China
Abstract：Traditional beamforming systems using dual closely-spaced microphones have various problems such as low-frequency-roll-off and limitations in suppressing competitive speech noises from multiple directions. This paper presents a two-step beamforming and maximum likelihood estimation algorithm. The algorithm first uses a WOLA filter for the time-frequency analysis for the speech mixture and then sets mask values to suppress background noise without low-frequency-roll-off based on the ratio of the two beamforming patterns, which have zeros at 0ånd 180°. A statistical model and the maximum likelihood estimation are then used to further enhance the speech. Tests indicate that the algorithm effectively recovers the energy distribution of the target signal and improves the signal-to-noise ratio without a low-pass filter or broadband compensation when the signal-to-ratio is low or multiple kinds of noises exist.
宫琴, 郑硕. 基于波束形成与最大似然估计的近距离双麦克风语音增强算法[J]. 清华大学学报（自然科学版）, 2018, 58(6): 603-608.
GONG Qin, ZHENG Shuo. Beamforming and maximum likelihood estimation for speech enhancement using dual closely-spaced microphones. Journal of Tsinghua University(Science and Technology), 2018, 58(6): 603-608.
[1] NOH J, JO H, PARK Y, et al. Acoustic-focusing headphone based on delay-and-sum beamforming[C]//Proceedings of 2010 International Conference on Control, Automation and Systems. Gyeonggi-do, Korea:IEEE Press, 2010:2061-2064. [2] KOKKINAKIS K, RUNGE C, TAHMINA Q, et al. Evaluation of a spectral subtraction strategy to suppress reverberant energy in cochlear implant devices[J]. Journal of the Acoustical Society of America, 2015, 138(1):115-124. [3] SALEEM N. Single channel noise reduction system in low SNR[J]. International Journal of Speech Technology, 2017, 20(1):89-98. [4] MAHIEUX Y, LE TOURNEUR G, SALIOU A. A microphone array for multimedia workstations[J]. Journal of the Audio Engineering Society, 1996, 44(5):365-372. [5] BRANDSTEIN M S, WARD E D B. Microphone arrays:Signal processing techniques and applications[M]. Berlin:Springer, 2001. [6] GRIFFITHS L J, JIM C W. An alternative approach to linearly constrained adaptive beamforming[J]. IEEE Transactions on Antenaas Propagation, 1982, 30(1):27-34. [7] GONG Q, CHEN Y S. Parameter selection methods of delay and beamforming for cochlear implant speech enhancement[J]. Acoustic Physics, 2011, 57(4):542-550. [8] MAJ J, WOUTERS J, MOONEN M. A two-stage adaptive beamformer for noise reduction in hearing aids[C]//Proceedings of 2001 Workshop on Acoustic Echo and Noise Control. Darmstadt, Germany:IEEE Press, 2001:171-174. [9] LAI C C, NORDHOLM S, LEUNG Y H. Design of steerable spherical broadband beamformers with flexible sensor configurations[J]. IEEE Transactions on Audio, Speech and Language Processing, 2013, 21(2):427-438. [10] LUO F L, YANG J, PAVLOVIC C. Adaptive null-forming scheme in digital hearing aids[J]. IEEE Transactions on Signal Processing, 2002, 50(7):1583-1590. [11] JACEK D, JACOB B, SOFIENE A. Direction of arrival estimation using the parameterized spatial correlation matrix[J]. IEEE Transactions on Audio, Speech and Language Processing, 2007, 15(4):1327-1339. [12] CHEN Y S, GONG Q. Broadband beamforming compensation algorithm in CI front-end acquisition[J/OL].[2017-10-01]. https://biomedical-engineering-online.biomedcentral.com/articles/10.1186/1475-925x-12-18. [13] YOUSEFIAN N, LOIZOU P C. A dual-microphone speech enhancement algorithm based on the coherence function[J]. IEEE Transactions on Audio Speech and Language Processing, 2012, 20(2):599-609. [14] AISSA-EL-BEY A, LINH-TRUNG N, ABED-MERAIM K, et al. Underdetermined blind separation of nondisjoint sources in the time-frequency domain[J]. IEEE Transactions on Signal Processing, 2007, 55(3):897-907. [15] 崔杰, 肖灵, 王玥, 等. 一种用于数字助听器的WOLA滤波器组的设计准则[J]. 应用声学, 2010, 29(1):36-42.CUI J, XIAO L, WANG Y, et al. A kind of design criterion for WOLA filterbanks used in digital hearing aids[J]. Applied Acoustics, 2010, 29(1):36-42. (in Chinese) [16] VARGA A, STEENEKEN H J M. Assessment for automatic speech recognition:Ⅱ. Noisex92:A database and an experiment to study the effect of additive noise on speech recognition systems[J]. Speech Communication, 1993, 12(3):247-251.
2018, Vol. 58 
