Audio Sync and Mixing: Common Mistakes and How to Avoid Them

The most common mistake I see on site is a single lip-sync check at line-up, followed by nothing for the next eight hours. Sync is not a setting you make once. Frame synchronisers drift, a new source is patched in, a graphics machine is swapped, and each of these can add a frame or two of delay to the picture without anyone touching the audio path.

A better habit is to treat the check as part of every transition in the day: before rehearsal, after any change to routing, and again before transmission or recording. It takes under a minute with a clap board or a simple test pattern and tone, and it costs far less than finding a half-second offset in the edit.

Crews are often reluctant because the check feels like an interruption. Build it into the running order instead, so the vision mixer, the sound supervisor and the floor all expect it, and nobody has to ask for it.

• Check sync after every routing or source change
• Use the same test method each time so results compare
• Log the measured offset, not just pass or fail

Meters are a guide, not a verdict. I have seen mixes sitting neatly at the target level that still sounded thin, because a presenter's radio microphone was clipping briefly at the transmitter and the desk only showed the tidy result downstream.

Listen on the same monitoring path the director uses, and then listen on something modest, such as small speakers or headphones of the kind your audience might own. A mix that only works on good studio monitors has not really been finished.

Set aside a few minutes in rehearsal for someone other than the mixer to listen without looking at the screen. Fresh ears catch harshness, hum and uneven dialogue levels that the person working the faders has stopped hearing.

Many mixing problems are decided long before the first fader moves. If gain is set too low at the preamp, the noise floor is lifted later when you compensate. If it is set too high, the distortion cannot be undone downstream.

Routing mistakes are quieter but just as costly. Auxiliary sends left pre-fader when they should be post, a talkback route leaking into the programme feed, or a mix-minus that was never properly built so a remote guest hears their own voice echoing back. Each of these is simple to prevent with a written signal path.

Draw the path on one page from source to transmission, mark every point where level or delay can change, and keep that page at the desk. When something sounds wrong, you can follow the line rather than guess.

• Set preamp gain for healthy headroom, then leave it alone
• Label every send as pre or post fader
• Build mix-minus before the guest arrives, not after

Autumn schedules often bring more remote contributors, and with them a different kind of sync problem. A guest on a network link arrives with their own delay, which can vary through a programme. Treating them like a studio microphone leads to talk-over and awkward gaps.

Agree a cue method in advance, such as a visual countdown or a clear verbal prompt, and keep the return feed as clean as you can. Do not rely on the guest's own monitoring to judge how it sounds on air.

For recorded programmes, ask for a clean local recording from the guest where possible. It will not fix a live delay, but it gives the edit something dependable when the live feed has dropouts or uneven levels.

A mix that only one person understands is a risk. If the sound supervisor is ill or the shift changes, the next operator inherits a desk full of undocumented routing, hidden processing and presets with unhelpful names.

Keep a short, current note of the desk layout, the inputs in use, any delay applied to compensate for picture, and who to contact if something fails. Name scenes by what they do, not by a date or initials.

This does not need to become a manual. One or two sides of paper, updated when something changes, saves more time than almost any piece of equipment, and it makes training new crew members much easier.

• Name presets by function
• Record every delay compensation and why it is there
• Keep the signal path page next to the desk

The last mistake is a matter of timing. Problems found during live transmission can only be patched; problems found in a rehearsal can be solved properly. The gap between those two outcomes is nearly always a matter of whether someone ran the full chain end to end beforehand.

Run a complete test with real sources, real graphics and the actual playout path, even if it is brief. Many faults only appear when everything is connected together, such as ground loops, unexpected delays or a return feed that has never been tested.

If your team lacks the time for this, that is useful information in itself, and it is a good reason to review the workflow rather than add pressure to the day.