8
lorentz
1y

A remarkably stupid but efficient technique I invented today to measure the latency of an audio feedback channel involving multiple hardware elements that is difficult to synchronize by itself:

1. Knock. Observe the echo in the feedback.
2.Try to knock in such a way that the physical sound more-or-less lines up with the feedback. The human brain is really good at this on average.
3. Once you often only hear one knock (as perfect synchronization as your ear can tell), record several minutes of audio
4. Stop knocking, count the additional knocks in the echo
5. Multiply the average delay between knocks on the recording by the number of additional knocks from step 4

Comments
  • 0
    What if one knock was lost in transmission and never got played back?
  • 0
    @electrineer Once you pick up the tempo, one knock can be lost and you'd still send the next one when it should have arrived because if you're completely synchronized you aren't actually knocking in response to the sound coming from the speakers - your response time would always produce an audible delay. The technique relies heavily on the human ability to pick up and maintain a rhythm using constant feedback.
  • 2
    @lorentz what if it happens when you've finished knocking?
  • 0
    @electrineer The extra knocks are already more of a failsafe than a critical step, it's possible to lose track if synchronization takes very long but for the most part I can keep track of my cycle lead compared to the echo I'm following.
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