All in your head: Exploring human-body communications with binaural
hearing aids
Scientists show how head tissue can be safely used as the transmission
medium for head-worn electronics
Date:
August 5, 2021
Source:
Tokyo University of Science
Summary:
Wearable technology seems all poised to take over next-generation
electronics, yet most wireless communication techniques are not
up to the task. To tackle this issue, scientists have delved deep
into human-body communications, in which human tissue is used as
the transmission medium for electromagnetic signals. Their findings
pave the way to more efficient and safer head-worn devices, such
as binaural hearing aids and earphones.
FULL STORY ========================================================================== Modern portable devices are the result of great progress in
miniaturization and wireless communications. Now that these devices can
be made even smaller and lighter without loss of functionality, it's
likely that a great part of next- generation electronics will revolve
around wearable technology. However, for wearables to truly transcend portables, we will need to rethink the way in which devices communicate
with each other as "wireless body area networks" (or WBANs). The usual
approach of using an antenna to radiate signals into the surrounding
area while hoping to reach a receiver won't cut it for wearables.
But, this method of transmission not only demands a lot of energy
but can also be unsafe from a cybersecurity standpoint. Moreover, the
human body itself also constitutes a large obstacle because it absorbs electromagnetic radiation and blocks signals.
==========================================================================
But what alternatives do we have for wearable technology? One promising approach is "human body communication" (HBC), which involves using the
body itself as a medium to transmit signals. The main idea is that some electric fields can propagate inside the body very efficiently without
leaking to the surrounding area. By interfacing skin-worn devices with electrodes, we can enable them to communicate with each other using
relatively lower frequencies than those used in conventional wireless
protocols like Bluetooth. However, even research on HBC began over two
decades, this technology hasn't been put to use on a large scale.
To explore the full potential of HBC, researchers from Japan, including
Dr.
Dairoku Muramatsu from Tokyo University of Science and Professor Ken
Sasaki from The University of Tokyo focused on using HBC for a yet
unexplored use: binaural hearing aids. Such hearing aid devices come
in pairs -- one for each ear -- and greatly improve intelligibility
and sound localization for the wearer by communicating with each other
to adapt to the sound field. Because these hearing aids are in direct
contact with the skin, they made for a perfect candidate application for
HBC. In a recent study, which was published in the journal Electronics,
the researchers investigated, through detailed numerical simulations, how electric fields emitted from an electrode in one ear distribute themselves
in the human head and reach a receiving electrode on the opposite ear,
and whether it could be leveraged in a digital communication system. In
fact, the researchers had previously conducted an experimental study on
HBC with real human subjects, the results of which were also published
in Electronics.
Using human-body models of different degrees of complexity, the
researchers first determined the best representation to ensure
accurate results in their simulations and then Once this was settled,
they proceeded to explore the effects of various system parameters
and characteristics, as Dr. Muramatsu puts it, "We calculated the
input impedance characteristics of the transceiver electrodes, the
transmission characteristics between transceivers, and the electric
field distributions in and around the head. In this way, we clarified
the transmission mechanisms of the proposed HBC system." Finally, with
these results, they determined the best electrode structure out of the
ones they tested. They also calculated the levels of electromagnetic
exposure caused by their system and found that it would be completely
safe for humans, according to modern safety standards.
Overall, this study showcases the potential of HBC and extends the applicability of this promising technology. After all, hearing aids
are but one of all modern head-worn wireless devices. For example, HBC
could be implemented in wireless earphones to enable them to communicate
with each other using far less power. Moreover, because the radio waves
used in HBC attenuate quickly outside of the body, HBC-based devices on separate people could operate at similar frequencies in the same space
without causing noise or interference.
"With our results, we have made great progress towardsreliable,
low-power communication systems that are not limited to hearing aids but
also applicable to other head-mounted wearable devices. Not just this, accessories such as earrings and piercings could also be used to create
new communication systems," concludes Dr. Muramatsu.
========================================================================== Story Source: Materials provided by Tokyo_University_of_Science. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Dairoku Muramatsu, Ken Sasaki. Transmission Analysis in Human Body
Communication for Head-Mounted Wearable Devices. Electronics,
2021; 10 (10): 1213 DOI: 10.3390/electronics10101213 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2021/08/210805150645.htm
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