Who doesn't love them?

The illustrated 15ms interval is the maximum tolerable delay of desynchronization between voice and image, according to this article .

The 2 sine pulse train is generated on the DAC output of SAMD21 (with Direct Digital Synthesis rather than PWM) and is triggered by the appearance of a 1 PPS pulse from the GPS.

Note that the oscilloscope (low) sampling frequency is deliberately set to 50 kSa/s to get near to the audio recording frequency in cinema (48 kHz). Fitting of the sin pulse will be done on the desktop with available python libraries.