DeBrunner V E, McKinney E D
School of Electrical Engineering, University of Oklahoma, Norman 73019-0631, USA.
J Acoust Soc Am. 1995 Jul;98(1):437-44. doi: 10.1121/1.414360.
This paper introduces directional microphones to adaptive array processing for hearing aid applications. Acoustic fixed arrays are designed to match a focused array gain pattern, while acoustic adaptive arrays are designed to attenuate interference noises with changing characteristics. However, as currently constructed, acoustic adaptive arrays cannot stay focused with a limited number of microphones available in a cosmetically acceptable hearing aid. In this paper, a technique is discussed that combines fixed and adaptive arrays in a system which enhances the desired signal while effectively attenuating interference speech and background noise. In particular, the design and performance of a directional adaptive least-mean-square (LMS) acoustic four-element array with a restricted geometry, where the array microphones are directional microphones, are examined. Simulations show that the directivity index of the directional adaptive array using four hypercardioid microphones is improved to between 8.6 and 11 dB. The array reduces the interference noises by 29.7 to 42.3 dB and provides a signal-to-noise ratio improvement of 11.5 to 12.2 dB over a single omnidirectional microphone. The sensitivity analysis is also discussed. It is concluded that the small size (four-element) microphone array can spatially filter interference noise effectively and so improve SNR performance significantly.
本文将定向麦克风引入用于助听器应用的自适应阵列处理中。声学固定阵列旨在匹配聚焦阵列增益模式，而声学自适应阵列旨在衰减具有变化特性的干扰噪声。然而，就目前的构造而言，声学自适应阵列在外观上可接受的助听器中，利用有限数量的麦克风无法保持聚焦。本文讨论了一种在系统中结合固定阵列和自适应阵列的技术，该系统在有效衰减干扰语音和背景噪声的同时增强所需信号。特别是，研究了一种具有受限几何形状的定向自适应最小均方（LMS）声学四元阵列的设计和性能，其中阵列麦克风为定向麦克风。仿真表明，使用四个超心形麦克风的定向自适应阵列的指向性指数提高到8.6至11 dB之间。该阵列将干扰噪声降低了29.7至42.3 dB，与单个全向麦克风相比，信噪比提高了11.5至12.2 dB。还讨论了灵敏度分析。得出的结论是，小尺寸（四元）麦克风阵列可以有效地在空间上过滤干扰噪声，从而显著提高信噪比性能。
