[Richard Crowley]

This isn’t really an audio question. It is a Mac OS question. You would likely get much better results asking this question somewhere where they discuss your hardware and operating system. You should also remember to disclose exactly what computer and operating system you are using so that you don’t waste time clarifying facts that should have been included in the original question.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Most of the budget-price wireless kits (mic + transmitter + receiver) include a cable (or the option for a cable) to plug into 3.5mm. These are the mics I would look at:

[Richard Crowley]

That is called “popcorn noise” (for obvious reasons).
The most likely cause is the microphone head itself is going bad.
Or the cable going to the mic head.
Or it is suffering from leakage from high humidity or other environmental causes.

Whether it is “repairable” depends on your schedule and budget.
There are expensive software tools that might be able to reduce the noise, but I wouldn’t bet on it.
You might be able to fix it manually, but it would take someone with good experience a lot of time.
Or you could re-shoot it if possible.

This is why we always MONITOR the audio on good headphones while we are recording.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Trying to record 50 people in an audience with random questions/comments isn’t realistic with the limits you have disclosed. Unless you are only going for “transcription-grade” audio. If you really want something usable for viewer-consumption, my BKM (Best Known Method) is to have the MC either repeat the question/comment or remind the presenter to repeat the question/comment. Or if there isn’t an MC, then a “room monitor” or “production assistant” or somebody. Explain to the client that it takes a bigger budget to violate the laws of acoustic physics. ????

Or you could just capture the “best-effort” transcription-grade audience audio and do a voice-over (or sub-title) in post-production editing to enhance the sub-standard audience audio.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Your symptom of “fairly loud hum” suggests a broken shield or a ground loop, etc. That is a rather different kind of problem than “EMI”. “Hum” is typically mains frequency (50Hz or 60Hz) and overtones (100Hz, 120Hz, etc.) While “RFI” is most often higher frequency buzz or even faint radio sounds (broadcast, police, etc.) Posting a sample of the interference would be very helpful in offering analysis and suggestions for resolving the problem.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

You need an attenuating cable. It takes the line-level from the source (venue FOH desk, etc.) and knocks it down to microphone-level to accommodate the input expectations of the transmitter. Exactly which kind depends on several factors not in evidence here. But here is an example of some attenuating cables and adapters:

https://search.sescom.com/search#w=attenuate&asug=

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Indeed, as Ty said, grounding (or AC coupling with a small capacitor) the XLR shell would be an easy first step to closing up some of the holes where interference is creeping in. Most modern XLR connectors have a separate internal tab for the shell. Simply solder a short, straight piece of wire between the shell tab and pin 1 ground. In cases where that causes a ground loop, then use a small capacitor (~0.01uF) instead of a piece of wire.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Neutrik makes a special connector with extra RFI/EMI shielding built-in.
Male: https://www.redco.com/Neutrik-NC3MXX-EMC-EMI-Protected-Male-XLR.html
Female: https://www.redco.com/Neutrik-NC3FXX-EMC-EMI-Protected-Female-XLR.html

Any cable with FOIL shield has 100% coverage. But foil shield cables are typically best for fixed installations.
The more common mic cables with braided or wrapped shields which may have only ~85% coverage.
There are some cables with double braided shield with nearly 100% coverage.

Redco will make custom cables with your choice of wire and connectors, and for a very sensible price.
https://www.redco.com/Custom-Cable.html
I have no connection with Redco other than a satisfied, paying customer.

Note, however, that the cable (and connectors) play only a partial role in solving RFI/EMI problems.
So don’t assume that even the very best cable and connectors will solve any RFI/EMI interference issue.

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

It is also very disappointing that products like the “H.264 Pro Recorder” do not support injecting analog (or AES) audio into on SDI or HDMI video stream. It has analog/digital audio inputs, but they are only used with the analog video input option. 🙁

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.

[Richard Crowley]

Since you have pretty much precluded any chance of using better equipment or procedure, there is at least one opportunity still available for possible improvement.

At least run a couple of rehearsals “interviewing” friends or accomplices using your proposed setup and learn the optimal settings and positions for everything.

And if at all possible insist on the interviewee at the far end using a hard-wired land-line telephone. (If there are any left on the planet??)

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Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.