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Actions Status License: MIT ggwave badge pypi npm

Tiny data-over-sound library.

Click on the images below to hear what it sounds like:




This library allows you to communicate small amounts of data between air-gapped devices using sound. It implements a simple FSK-based transmission protocol that can be easily integrated in various projects. The bandwidth rate is between 8-16 bytes/sec depending on the protocol parameters. Error correction codes (ECC) are used to improve demodulation robustness.

This library is used only to generate and analyze the RAW waveforms that are played and captured from your audio devices (speakers, microphones, etc.). You are free to use any audio backend (e.g. PulseAudio, ALSA, etc.) as long as you provide callbacks for queuing and dequeuing audio samples.

Here is a list of possible applications of ggwave with a few examples:

Try it out

You can easily test the library using the free waver application which is available on the following platforms:

Download on the App Store Get it on Google Play Get it from the Snap Store

Browser demos

# audible example
curl -sS '!' --output hello.wav

# ultrasound example
curl -sS '!&p=4' --output hello.wav

Technical details

Below is a short summary of the modulation and demodulation algorithm used in ggwave for encoding and decoding data into sound.

Modulation (Tx)

The current approach uses a multi-frequency Frequency-Shift Keying (FSK) modulation scheme. The data to be transmitted is first split into 4-bit chunks. At each moment of time, 3 bytes are transmitted using 6 tones - one tone for each 4-bit chunk. The 6 tones are emitted in a 4.5kHz range divided in 96 equally-spaced frequencies:

Freq, [Hz] Value, [bits] Freq, [Hz] Value, [bits] ... Freq, [Hz] Value, [bits]
F0 + 00*dF Chunk 0: 0000 F0 + 16*dF Chunk 1: 0000 ... F0 + 80*dF Chunk 5: 0000
F0 + 01*dF Chunk 0: 0001 F0 + 17*dF Chunk 1: 0001 ... F0 + 81*dF Chunk 5: 0001
F0 + 02*dF Chunk 0: 0010 F0 + 18*dF Chunk 1: 0010 ... F0 + 82*dF Chunk 5: 0010
... ... ... ... ... ... ...
F0 + 14*dF Chunk 0: 1110 F0 + 30*dF Chunk 1: 1110 ... F0 + 94*dF Chunk 5: 1110
F0 + 15*dF Chunk 0: 1111 F0 + 31*dF Chunk 1: 1111 ... F0 + 95*dF Chunk 5: 1111

For all protocols: dF = 46.875 Hz. For non-ultrasonic protocols: F0 = 1875.000 Hz. For ultrasonic protocols: F0 = 15000.000 Hz.

The original data is encoded using Reed-Solomon error codes. The number of ECC bytes is determined based on the length of the original data. The encoded data is the one being transmitted.

Demodulation (Rx)

Beginning and ending of the transmission are marked with special sound markers (#13). The receiver listens for these markers and records the in-between sound data. The recorded data is then Fourier transformed to obtain a frequency spectrum. The detected frequencies are decoded back to binary data in the same way they were encoded.

Reed-Solomon decoding is finally performed to obtain the original data.


The examples folder contains several sample applications of the library:

Example Description Audio
ggtag Sound-programmable e-paper badge PDM mic
ggwave-rx Very basic receive-only program SDL
ggwave-cli Command line tool for sending/receiving data through sound SDL
ggwave-wasm WebAssembly module for web applications SDL
ggwave-to-file Output a generated waveform to an uncompressed WAV file -
ggwave-from-file Decode a waveform from an uncompressed WAV file -
waver GUI application for sending/receiving data through sound SDL
ggwave-py Python examples PortAudio
ggwave-js Javascript example Web Audio API
spectrogram Spectrogram tool SDL
ggweb-spike Android example using a WebView to wrap ggwave into a simple app WebAudio
buttons Record and send commands via Talking buttons Web Audio API
r2t2 Transmit data through the PC speaker PC speaker
ggwave-objc Minimal Objective-C iOS app using ggwave AudioToolbox
ggwave-java Minimal Java Android app using ggwave
ggwave-fm Transmit ggwave messages with HackRF Radio
esp32-rx Transmit and receive messages using ESP32 -
rp2040-rx Transmit and receive messages using Raspberry Pi Pico (RP2040) -
arduino-rx Transmit and receive messages using Arduino RP2040 -
arduino-tx Transmit messages using Arduino Uno -
arduino-rx-web Receive messages from Arduino Uno Web Audio API

Other projects using ggwave or one of its prototypes:

  • wave-gui - a GUI for exploring different modulation protocols
  • wave-share - WebRTC file sharing with sound signaling


Dependencies for SDL-based examples

$ sudo apt install libsdl2-dev

[Mac OS with brew]
$ brew install sdl2

$ pacman -S git cmake make mingw-w64-x86_64-dlfcn mingw-w64-x86_64-gcc mingw-w64-x86_64-SDL2

Linux, Mac, Windows (MSYS2)

# build
git clone --recursive
cd ggwave && mkdir build && cd build
cmake ..

# running


git clone --recursive
cd ggwave
mkdir build && cd build
emcmake cmake ..


pip install ggwave

More info:


npm install ggwave

More info:


Available as a Swift Package:

Installing the Waver application

Get it from the Snap Store


sudo snap install waver
sudo snap connect waver:audio-record :audio-record

Mac OS

brew install ggerganov/ggerganov/waver