Audio Transfer — Send

Transfer a file through the room using sound only. The sender first listens to the local spectrum and chooses the quietest supported frequency band.

Open audio receiver

File Data chunk size Output level

Select a file, then analyze the room.

File —

Size —

Selected band —

Room score —

Transfer ID —

Chunks —

Receiver not synced

Progress —

Control beacon signals 42

Control packets sent 0

Physical control signals sent 0

Data packets sent 0

Data symbols sent 0

Room spectrum

The sender measures only the frequency energy needed to choose a band. It does not record, upload, or save microphone audio.

No spectrum scan yet.

How synchronization works

The sender announces the chosen frequency band using separator-framed redundant FSK with an explicit separator tone on a deliberately slow, wide-spaced control channel designed for ordinary speakers and microphones. The receiver decodes that beacon and replies with an acoustic ACK containing the same transfer ID. Only then does the sender switch to the chosen data frequencies.

When the receiver has rebuilt the file and verified SHA-256, it answers with a final completion packet over the control band.

All transfer modes Switch to Visual Transfer