Crop audio waveform precisely

I need the spoken line to start exactly on the beat at 00:00:12.7. Zoom into the audio track, nudge the waveform so the plosive at the start lines up with the video beat, and trim any silence before it without shifting the rest of the track. Save that change so the cut starts clean at the right frame.

Before I hand this to the sound designer, make the dialogue easy to edit: show the full waveform with a larger vertical scale, center on the section from 00:00:10 to 00:00:16, and mark probable phoneme onsets. Trim leading silence and create a version snapped to frame boundaries, then flag any background noise above -30 dB that will need cleanup.

I moved the audio to align a line and the speaker's mouth now mismatches by one frame at 00:00:13. I can't tell if the original audio has a hidden sample offset or if my nudge was imprecise. Which explanation is most likely, and what single, precise check will tell me if the file carries an embedded offset versus a misalignment I can correct by re-snapping to the video frame?

Each week I re-align hosts' lines because their audio files arrive at inconsistent start points and levels, costing me an hour per episode. Should I require contributors to record a three-count slate and fixed mic gain, or should I build a short import routine that trims leading silence and normalizes gains automatically? Tell me which habit will save the most time and how to enforce it with the team.