gugajazz / Sine_messaging

A website that uses javascript's web apis to send and receive data wirelessly between devices using only sound (At inaudible frequencies by default).

What Sine-messaging is

A website that uses javascript's web apis to send and receive data wirelessly between devices using only sound (At inaudible frequencies by default).
Regarding the front-end it was built using the React library.

How to use it

Navigate to https://gugajazz.github.io/Sine_messaging on a chromium based browser and continue reading.

How it works

The text is converted to binary using Utf-8.
Using a AudioContext oscilator it generates and transmits through the speakers a sine wave of a specified frequency for some pre-determined milliseconds.
The frequency depends on the pair of bits currently being broadcast.
Ex:
00 -> 18200hz
01 -> 18400hz
10 -> 18600hz
11 -> 18800hz

The listener then analises the amplitude of each frequency using a fast fourier transform to detect the distinct signature of a signal over the background noise.
When that happens, it'll log the frequencies received over the duration of the message.
Finally, it will read the data and decode it to binary by counting how long each sine wave lasted.
Ex: In a very simplified way, if it recorded the following frequenncies during the transmission 18400hz, 18800hz, 18200hz, 18600hz, because we know what pair of bits each frequency represents, we know that the signal was 01110110 and can decode it to obtain that character v.

Send data

Type your message ( Expect around 1s for each character to be sent on default settings )

Receive data

While waiting the red light will look as shown

When a signal is coming in ripples will appear as shown

Warnings

By default, sine-messaging uses frequencies between 18200hz and 18800hz. Frequencies in this range usually aren't audible by humans but can and will still cause hearing damage if heard at unsafe levels.
It is then recommended that for short range communication ( <5m ) the users use a low volume, which usually is enough, and increase it progressively if necessary to achieve reliability opperation at longer ranges.

Results

This project was mostly a proof of concept to show that data can be transmited through sound at inaudible frequencies using common, every-day hardware, across platforms and fully offline (excluding loading the website).

With that being said, there are multiple paths that could, and perhaps will, be taken in the future to improve performance and reliability. The default settings aim to work across the widest range of hardware, from phones to tablets, PCs and maybe some fridges. For those reasons they can be tweaked to vastly improve the trasmition times.

Results with default settings:

• Bit rate:
  Little over 8 bits / second. Aka 1 character a second or a Baud rate of 1.

• Range:
  Multiple meters while remaining at a safe volume and small error rate.

Changing default settings:

In order for the transmission and reception of data to work it's necessary that every device communicating shares the same values for their settings.
This is the case by default but must be taken in to consideration when chaging the settings.