That could be overmodulation of the wireless. Many budget level systems will have a transmitter side gain adjustment that is designed for a wide range of mic impedances, so it’s easy to overdrive the RF link. The level you see on tape (or on camera meters) would not show any unusually high levels. The overmodulation occurs on parts of audio that reveal it most – low and high end. Midrange is more forgiving and, if it’s borderline over, would not have the problem. These systems also have suspect compander circuits that could contribute to the “swooshy” effect. The best way to prevent this from occuring again is to wear good, over-the-ear, headphones during th entire take.
You said mic placement seems ok – is it within 12 inches of the mouth? If so, does it have some wind protection (windscreen, rycote, etc.)? Some speakers can produce downward plosives that could hit the mic and produce the results you described. Again, the best way to prevent this from occuring again is to wear good, over-the-ear, headphones during the entire take.
As for fixing the problem, it’s probably safe to say that you can’t eliminate it, but that type of noise usually occurs at a lower frequency than your average female voice, so try a shelving filter (lo cut) starting around 180hz and go up until you hear improvement. Also try a de-esser. It is used to reduce silibance and may be able to help the “breathy” portions. Most de-essers are available as plug-ins for DAWs.
If you paid the crew, the soundperson should be held responsible. This is one of those businesses where one persons actions, or inaction, can negate the efforts of everyone else on the crew.
I don’t know why they were using a wireless – a wired, overhead boom is best – unless frame composition make it impossible.
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