Новогодний смех (New Year Laughter)

bug-makers

Task: 73-second stereo WAV of New Year bells and laughter hiding a flag in the ultrasonic band. Solution: a faint ~20 kHz carrier near Nyquist is on/off-keyed; isolate it with a bandpass filter, extract the amplitude envelope, threshold to ON/OFF, and decode short/long pulses as binary OOK bits into ASCII.