Place it at the turning point of a short edit, right after the setup and just before the payoff, then follow it with a bigger reaction such as Oh My God Wow to escalate the moment, or use Huh before it when the confusion needs to build first.
Über diesen Sound
This is a short human 'ah' lasting about a second and a half, spoken as one clear exclamation with no other words, music or effects behind it. It gives a light sense of surprise and sudden realisation, quick and easy to read without feeling dramatic or overplayed.