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Scientists at Tokyo University of Science have demonstrated the potential of human body communications by designing binaural hearing aids that safely use head tissue as a medium for transmitting electromagnetic signals. Advances in miniaturization and wireless communications have given rise to wearable devices for medical monitors and AR / VR headsets. While the traditional method of transmitting signals relies on wireless technology, for portable devices to truly transcend, they will require a more efficient form of communication, such as wireless body networks (WBANs). These networks have their drawbacks, including being dangerous from a cybersecurity point of view, absorbing electromagnetic radiation and having a tendency to block signals.
Another solution would be to take advantage of human body communication (HBC), which use the human body to transmit signals. HBCs work by tapping into electric fields that propagate inside the human body, which can then be used with skin-worn devices equipped with electrodes to communicate with other devices using low frequencies. Although the technology is over two decades old, little has been done to use it on a large scale.
To demonstrate its potential, scientists designed their binaural hearing aids, which improve intelligibility and localization of sound for the wearer by communicating with each other to adapt to the sound field. In a recent to study, the scientists, led by Dairoku Muramatsu, studied – via detailed digital simulations – how electric fields emitted by an electrode in one ear are distributed in the human head and reach a receiving electrode on the opposite ear, and whether they could be operated in a digital communication system.
Not only did they find they could do it, but they could do it safely as well. They also explored the effects of various system parameters and characteristics, leading them to determine the best electrode structure to use in HBCs.
The study shows the potential of HBCs through the use of binaural hearing aids, but this is only the beginning of their potential use. Muramatsu answered our questions about the technology – its advantages, potential applications and disadvantages.
1: Does skin composition make a difference with HBC? For example, some have more layers, while others tend to sweat more.
Yes, the composition of the skin and the sweat affect the characteristics of the antenna (electrodes) and the communication quality of HBC. As an approach to this problem, we investigated the important characteristics of HBc in relation to individual differences through experience with real human subjects. The results show that individual differences can be suppressed by selecting appropriate design parameters such as carrier frequency. These results were also published in the journal Electronic.
2: While HBC devices can be used by the individual, would it be possible to communicate with others using the same technology? Is distance a factor?
Yes, HBC can be used for multi-user communication as well as single-user communication. Communication requires physical contact between users, like a handshake, and will not work if there is a distance between them. Read more via the Association for Computer Machinery.
3: Does the environment play a role? Would it be possible to use the HBC devices underwater or in extremely hot or cold areas?
In the example of underwater communication, general radio communication is not available because electromagnetic waves are absorbed by seawater, which contains a large amount of salt. Therefore, ultrasonic waves and light are generally used for wireless communication underwater. Since HBC uses the human body as the transmission channel instead of seawater, it is possible that HBC achieves low loss wireless communication even underwater. The temperature does not affect the mechanism of HBc. However, since HBC devices are composed of general electronic circuits, the needs of the environment in which these circuits may operate are taken into account.
The researchers reported that measurements using a prototype portable antenna and 22 human subjects revealed that HBC is “robust against variations of individual users in terms of voltage standing wave ratio”.