Microphone Array Embedded in Eyeglasses
The advantages of an improved signal-to-noise ratio (SNR) are well known. When multiple microphones work together in a "microphone array," advanced analysis and processing of sounds, with respect to speech and noise acoustic cues, spatial characteristics, and more, can occur. An improved SNR allows people wearing hearing aids to perceive speech more easily, thus increasing the likelihood of improved (i.e., lower) speech reception thresholds and improved (i.e., higher) speech intelligibility. Chung (2004) and Luts et al (2004) addressed many of the issues, advantages, and challenges associated with array-based microphones.
Mens (2011) recently described a four-microphone array embedded in eyeglasses to evaluate the benefit of the microphone array located more anteriorly than the traditional pinna/ear location. Two groups of subjects participated; 15 people with hearing loss and five people with normal hearing were evaluated. The eyeglass-based four-microphone array has a sampling rate of 16,000 Hz and a bandwidth of approximately 200 to 6400 Hz. The averaged directivity index (DI) was determined to be approximately 9 dB.
For both groups, the speech reception threshold in noise improved between 6 and 6.5 dB while using the four-microphone array, as compared to a more traditional single-microphone, omni-directional BTE system. The anterior microphone placement outperformed the more traditional location primarily due to a longer array, resulting in a higher directionality index and improved speech understanding in noise.
For More Information, References, and Recommendations
Mens LHM. (2011) Speech Understanding in Noise with an Eyeglass Hearing Aid: Asymmetric Fitting and the Head Shadow Benefit of Anterior Microphones. International Journal of Audiology 50:27-33.
Luts H, Maj JB, Soede W, Wouters J. (2004) Better speech perception in noise with an assistive multimicrophone array for hearing aids. Ear & Hearing 25(5):411-420.
Chung K. (2004) Challenges and recent developments in hearing aids. Part I. Speech understanding in noise, microphone technologies and noise reduction algorithms. Trends in Amplification 8(3):83-124.