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Sensors 2015, 15(9), 23402-23417;

Wearable Sensing of In-Ear Pressure for Heart Rate Monitoring with a Piezoelectric Sensor

Medical IT Convergence Research Center, Korea Electronics Technology Institute, Seongnam 463-816, Korea
Samsung Advanced Institute of Technology, Samsung Electronics Co. Ltd., Suwon 443-803, Korea
Creative Innovation Center, LG Electronics Co. Ltd., Seoul 137-893, Korea
Industry-Academic Cooperation Foundation, Dongguk University, Seoul 100-715, Korea
Author to whom correspondence should be addressed.
Academic Editor: Steffen Leonhardt
Received: 3 August 2015 / Revised: 9 September 2015 / Accepted: 10 September 2015 / Published: 16 September 2015
(This article belongs to the Special Issue Noninvasive Biomedical Sensors)
Full-Text   |   PDF [1177 KB, uploaded 16 September 2015]   |  


In this study, we developed a novel heart rate (HR) monitoring approach in which we measure the pressure variance of the surface of the ear canal. A scissor-shaped apparatus equipped with a piezoelectric film sensor and a hardware circuit module was designed for high wearability and to obtain stable measurement. In the proposed device, the film sensor converts in-ear pulse waves (EPW) into electrical current, and the circuit module enhances the EPW and suppresses noise. A real-time algorithm embedded in the circuit module performs morphological conversions to make the EPW more distinct and knowledge-based rules are used to detect EPW peaks. In a clinical experiment conducted using a reference electrocardiogram (ECG) device, EPW and ECG were concurrently recorded from 58 healthy subjects. The EPW intervals between successive peaks and their corresponding ECG intervals were then compared to each other. Promising results were obtained from the samples, specifically, a sensitivity of 97.25%, positive predictive value of 97.17%, and mean absolute difference of 0.62. Thus, highly accurate HR was obtained from in-ear pressure variance. Consequently, we believe that our proposed approach could be used to monitor vital signs and also utilized in diverse applications in the near future. View Full-Text
Keywords: wearable heart rate monitoring; in-ear pressure variance; piezoelectric sensor wearable heart rate monitoring; in-ear pressure variance; piezoelectric sensor

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Park, J.-H.; Jang, D.-G.; Park, J.W.; Youm, S.-K. Wearable Sensing of In-Ear Pressure for Heart Rate Monitoring with a Piezoelectric Sensor. Sensors 2015, 15, 23402-23417.

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