Send text from one device to another using only sound. Once this page is open it needs no
network at all — the message travels as sound waves through the air.
1 · Test on THIS device first
Plays a message from your speaker and decodes it back
through your own mic — proving the acoustic link works before you try two phones.
2 · Send
Turn volume to max for more range. Higher volume + a quiet room = longer distance. ~10 chars/sec.
3 · Receive
sync: —4–9 kHz · orange=sync green=datalevel: 0%
Idle. Press “Start listening,” then Send from the other device.
How to prove it works with no internet
Open this page on both phones (internet on, just to load). Tap “Add to Home Screen” to keep it offline.
Grant microphone permission on the receiving phone.
Put both phones in Airplane Mode ✈️ (kills cellular, WiFi, Bluetooth — not the speaker/mic).
On phone B tap Start listening; on phone A type a message and tap Send.
It arrives with every radio off — proof it’s the sound.