Sony Walkman: let’s use human body instead of headphone wires
Tired of the dangling headphone wires from your iPod or Walkman? Wires? Who need wires anymore? Sony says that we will be able to do without them soon. Instead we will use our own bodies to wirelessly transmit audio signal from the music player to the headphones.
At least that’s what their patent application for “Human body communication system and communication device” promises. Apparently Sony has been conducting research in this field and now has some results worth announcing. And it works like this:
Every human body has properties as a conductor and properties as a dielectric. Both of them can be used for data transmission. But the conductor properties are not really suitable for data transmission use – just try running even a a weak electric current through your body and you’ll know why. And a stronger version of this process is used in the electric chairs…
So the conductors are out. That leaves us with dielectric properties and electrostatic field generated by human body. And here Sony got some interesting results. Just like in any modern audio system they took analog audio signal, converted it into a digital signal of particular frequency, amplified it and used quasi-electrostatic field of human body to data-transmit the signal as a potential difference from a transmission electrode in the player device.
It turns out that the reception electrode installed in the vicinity of the human body (e.g. in the headphones) is able to read this change of potential. Add additional signal amplifier, demodulation and conversion of digital signal into audio output and Voila. You’ve got a sound in a headphone speaker.
There were problems with interference from external electromagnetic fields, loss of signal, insufficient bandwith in particular frequencies. But Sony researchers found that in a 500 kHz -3 MHz frequency bands have sufficient bandwith to transmit 48-kbps audio signal in ATRAC3plus format used in most Sony players today.
So, goodbye headphone wires, soon we will be using our bodies instead.