Experiments Alpha

Acoustic Beam

Send a file from one device to another with sound — no internet, no Bluetooth, no USB. The sender's speakers play a sequence of audio chirps; the receiver's microphone reassembles the file. Everything runs in your browser.

Alpha — audio transfer is experimental and may need a quiet room and close device spacing.

Drop a file here

or click to browse

Type a message (beamed as message.txt) 0 chars · 0 bytes

Chunk size (bytes) Volume

60%

Passphrase (optional — AES-GCM 256, PBKDF2 250k)

Without a passphrase the transfer is not encrypted — anyone within earshot can decode it.

Compress (gzip before chunking — faster for text) Fountain (Luby Transform — missed packets don’t cost a full loop)

Pick a file to begin. Audio transfer is slow — keep chunk size small.

Waveform will appear here while transmitting.

Packet 0 / 0 · Loop 0

Place the two devices close together with a clear line of sound. The sequence loops automatically until every chunk has been received.

How it works

The sender picks a file. The browser computes its SHA-256, splits the bytes into chunks, and encodes each chunk as a base45 string (same pipeline as QR Beam).
Each base45 string is broadcast as an audio packet: a 200 ms preamble tone, a length header, the payload as 8-tone MFSK chirps (50 baud), and a CRC-16 footer.
The receiver opens this same page on another device, switches to the Receive tab, and starts the microphone. The spectrogram shows incoming audio energy.
The decoder watches for the preamble tone, demodulates the symbols, validates the CRC, and feeds each packet to the QR Beam reassembler. The SHA-256 is verified before the download is offered.
No server. No internet. The file never leaves your browser.

Acoustic Beam is much slower than QR Beam (≈11 bytes/sec of source). It works best for small text messages and tiny files in a quiet room.