Clinical Medicine Research
Volume 7, Issue 5, September 2018, Pages: 103-118
Received: Sep. 6, 2018;
Accepted: Sep. 26, 2018;
Published: Oct. 26, 2018
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Xubao Zhang, Research & Development, Sonova Unitron, Oticon, Canada; Electronic Engineering Department, Xi’an Electronic Science and Technology University, Xi’an, China
We present extensive experimental data to objectively evaluate the benefits and limitations of common directional microphones in real-world sound fields. The microphones include a conventional directional microphone(DM), a balanced DM, etc., plus the Omni microphone (mic) as a benchmark. The evaluation focuses on noise outputs, signal-to-noise ratios(S/Ns) and distortions; the real-world sounds include male voices, female voices, babble noises, white noises and talking interferences. Each type of noises is at 4 or 5 levels, from 30 to 70 dB SPL, at 10 dB step, and each talking interference is at 3 levels: 50, 60 and 70 dB SPL. The research methods include analytically deriving sensitivity-gains, statistically calculating the three mics’ outputs, experimentally viewing waveforms and spectra, and using large-sample wave files for a high confidence level. According to the experimental results, this paper concludes that 1) for a conversation in a quiet field, in soft or low noise field, the common DMs achieve comfortable S/Ns: 7 to 33 dB, similar to what the Omni mic does; 2) for a conversation in low, competing or strong talking interference fields, the common DMs achieve about 16 dB better S/N than the Omni mic does; 3) for a conversation in competing or strong surrounding noise field, the common DMs do not achieve beneficial S/N to understand speech; the common DMs’ noises are close to the Omni mic noise; 4) in various experiments, the balanced DM preserve speech fidelity well as the Omni mic does, while the conventional DM does poorly. This paper further introduces the Simulink experimental manipulations, such as digital FIR filters’ design, stereo channels’ wave files creation, etc., in the Appendix.
Benefits and Limitations of Common Directional Microphones in Real-World Sounds, Clinical Medicine Research.
Vol. 7, No. 5,
2018, pp. 103-118.
Wu, Y. H. Gaining new insights about directional hearing aid performance, 20Q with Gus Mueller, 2013, Feb. www.audiologyonline.com.
Chalupper, J., Wu, Y. H. Improving effectiveness of directional microphones with soft level directivity, Hear J., 2011, 64(7), 44-49. Doi:10.1097/01.hj.0000399880.84848.a1.
Nyffeler, M., Dechant, S. Field study on user control of directional focus: benefits of hearing the facets of a full life, Hear Rev., 2008, 16(1), 24-28.
Nyffeler, M. Auto ZoomControl - Automatic change of focus to speech signals of interest, Field Study News, Sept. 2010. www.phonakpro.com.
Jorge Mejia, Harvey Dillon, Elizabeth Beach, Margo McLelland, Mridula Sharma, et al. Loss of speech perception in noise -- causes and compensation, International symposium on auditory and audiological research (ISAAR) 2015, 205-215.
Lindley, G., Schum, J. D., Fuglholt, L. M. Directionality and noise reduction in pediatric fittings, Hearing Review, 2009, 16(5), 34-44.
Chalupper, J., Wu, Y. H., Weber, J. New algorithm automatically adjusts directional system for special situations, The Hearing Journal, 2011, 64(1), 26-33. Doi:10.1097/01.hj.0000393211. 70569.5c.
Xubao Zhang, Yu-Hsiang Wu. Technologies and performances of directional microphones in modern hearing aids, Journal of Audiology and Speech Pathology, 2015, 23(3), 301-306.
Gnewikow, D., Ricketts, T., Bratt, W. G., Mutchler, C. L. Real-world benefit from directional microphone hearing aids, J. Rehabil Res Dev., 2009, 46(5), 603- 618. Doi:10.1682/jrrd.2007.03.0052.
Bentler, A. R. Effectiveness of directional microphones and noise reduction schemes in hearing aids: a systematic review of the evidence, J. Am Audiol., 2005, 16, 473-484. Doi:10.3766/jaaa. 16.7.7.
Zhang, X. Polar plots of a directional microphone with real-world sounds and its spectrum distortion, EPH -- International Journal of Science and Engineering, 2017, 3(7), 1-11.
Thomapson, C. S., LoPresti, L. J., Ring, M. E., Nepomuceno, G. H., et al. Noise in miniature microphones, J. Acoust Soc. Am. 2002, 111(2), 861-866. Doi:10.1121/1.428971.
Ryoo, K., Chilukuri, M., Jung, S. A low power and low noise pre-amplifier circuit for hearing aid devices, Circuits and Systems Conference (DCAS) IEEE, Texas, 2016. Doi: 10.1109/dcas.2016.7791128.
Directional Microphones, Sonion. http://www.sonion.com/wp/products/hearing- instrument-components/microphones/directional-microphones/.
Voice Samples-LAMP Words for Life. https://aacapps.com/lamp/voices.
Mahendru, H. C., Khanna, R. Spectral analysis of various noise signals affecting mobile speech communication, International Journal of Scientific & Engineering Research, 2014, 5, 1087-1093.
Fontan, L., Tardieu, J., Gaillard, P., Woisard, V., Ruiz, R. Relationship between speech intelligibility and speech comprehension in babble noise, J. Speech Lang Hear Res., 2015, 58, 977-986. Doi: 10.1044/2015_jslhr-h-13- 0335.
Venema, H. T. Compression for Clinicians, 2nd Ed., Thomson Delmar Learning, 2006.