New Technology Turns Earphones Into Pulse Wave Sensor

2013/10/25 17:22
Takuya Otani, Nikkei Electronics & Digital Health Online

The Kaiteki Institute Inc and Bifrostec Inc demonstrated a technology of detecting pulse waves with earphones at Healthcare Device Exhibition 2013, which runs from Oct 23 to 25, 2013, in Yokohama, Japan.

In the demonstration, earphones that were sold at a mass home electronics retailer for a price of ¥809 (approx US$8.3) were used.

The new technology leverages the pressure change in the enclosed space of the ear canal when earphones are worn. In accordance with the movement of arteries, the eardrum is moving at a frequency of about 1Hz, Bifrostec said. The pressure change in the enclosed space is caused by this movement of the eardrum and detected by the earphones functioning as microphones.

However, earphones do not always make a completely-enclosed space. And ambient noise can affect the detection capability. The Kaiteki Institute and Bifrostec enabled to detect pulse waves with commercially-available earphones by using their own signal processing technologies to deal with such problems, they said.

The new technology does not require making any changes to earphones. Therefore, if the necessary signal processing function is added to a smartphone or audio device, it becomes possible to check pulse periodically (or by operating the device) while listening to music.

"There are many people who listen to music while jogging," Bifrostec said. "With the new technology, it becomes possible to measure their pulse waves without any special effort."

The Kaiteki Institute and Bifrostec also exhibited a ring-shaped pulse wave sensor based on a similar principle. It is equipped with a MEMS microphone, and the pressure change in the enclosed space made by wearing the ring is detected with the microphone.

Furthermore, they showed an application software that checks the state of autonomic nerves by using the pulse data obtained with earphones or the ring-shaped sensor. It detects changes in the state of autonomic nerves based on the fluctuation of pulse wave's peak-to-peak interval. All of those exhibited devices were prototypes.

The Kaiteki Institute is a wholly-owned subsidiary of Mitsubishi Chemical Holdings Corp. Bifrostec is a venture firm established by former employees of major electronics companies including Sony Corp.