The referee’s whistle is a tried-and-tested way of sending a signal to stop or start play. But could it also carry a secret burst of digital information?
That is the question posed by Pea Whistle Steganography, a post by signals hacker Oona Räisänen which explores whether a traditional pea whistle can encode binary information in a series of frequency pulses.
The answer: yes, kind of, though constructing a physical data-encoding whistle is left as an exercise for the reader. There is, however, some working Perl code that synthesises a wav file containing your pea-coded message of choice.
See Oona’s blog for countless more excellent DSP explorations.