Acoustic

Data over sound

Two devices, one room, no network required.

Channel modes

Basic

A telephony-grade profile carried on eight tones drawn from the classic DTMF row and column frequencies (697, 770, 852 and 941 hertz crossed with 1209, 1336, 1477 and 1633 hertz). Sixteen symbols per cycle, twenty-five symbols per second, heavy Reed-Solomon RS(15,9) parity. Effective throughput is about 5 to 8 bytes per second after error correction. A short plain-text message arrives in 10 to 15 seconds and survives a normal voice call.

+ Survives any voice codec, including phone calls- Audible: sounds like a brief telephony tone burst

Ultrasonic

A multi-tone carrier in the inaudible 17 to 19 kilohertz band, twenty symbols per second, around 10 to 15 bytes per second of throughput. A 5-character message arrives in about three seconds, a 50-character one in about six. Range sits between 30 cm and roughly 1 m and does not cross the room. Hearing-safe, comparable in level to ordinary music.

+ Inaudible to people in the room- Requires modern broadband audio hardware on both phones

Strong points

Basic profile passes cleanly through any voice channel, including a Telegram or WhatsApp voice note, a regular phone call, and even a legacy landline. Every voice codec was designed to carry these tones.
Ultrasonic profile is inaudible to the people in the room and rides at the upper edge of adult hearing.
Same-room range of roughly a few metres for Basic and 30 cm to about 1 m for Ultrasonic.

Trade-offs

Short-message oriented, not a file transport. Throughput is around 5 to 8 bytes per second on Basic and 10 to 15 bytes per second on Ultrasonic.
Ultrasonic needs modern broadband speakers and microphones on both ends. Older budget phones whose audio response rolls off below 17 kilohertz cannot carry the signal.

Technical specifications

Acoustic channel modes

Two user-visible sub-modes are exposed in the app: a telephony-grade Basic profile and an inaudible Ultrasonic profile.

Sub-mode	Carrier	Throughput	Effective range	Audible?	Best for
Basic (DTMF-class)	Eight tones, 697 / 770 / 852 / 941 Hz rows crossed with 1209 / 1336 / 1477 / 1633 Hz columns. Sixteen symbols, twenty-five symbols per second, Reed-Solomon RS(15,9) parity.	~5 to 8 bytes per second after error correction. 10 to 15 seconds for a 5 to 50 character message.	Up to a few metres in a quiet room. Also survives a normal phone call or a Telegram / WhatsApp / Bale / Soroush voice note.	Yes (telephony tone burst)	Same-room transfers, harsh acoustic environments, transmission over a voice call, situations where the parties cannot see each other.
Ultrasonic	Multi-tone carrier in the inaudible 17 to 19 kilohertz band. Twenty symbols per second.	~10 to 15 bytes per second. About 3 seconds for a 5-character message, about 6 seconds for 50 characters.	30 cm to roughly 1 m. Does not carry beyond the room.	No (above adult hearing range)	Same-room transfers where modern audio hardware is present on both phones and an inaudible transmission is preferred.

Values measured with the standard speaker and microphone of a current-generation mobile device at one metre under indoor conditions. Real-world performance varies with room acoustics, speaker quality and microphone response.

Get started

Two devices. One shared password. No intermediary.

Install Taftan on both devices, agree on the password through a separate channel beforehand, and run a quick test transfer using whichever channel fits your situation.

Download the application Read the documentation