[Richard Crowley]

I don’t see any mention of the camera(s?).
Are you using such low-end camera(s?) that you must do double-system sound?
You haven’t really established why you are using double-system sound to begin with.

Although I started out as a sound person before ever getting involved with video, and I have TONS of audio gear, I will almost certainly record directly to the camcorder when I start shooting video for some instructional/blog things in a month or two.

There are reasons for using double-system sound. But shooting simple 1 (or 2) microphone instructional video hardly requires that much fiddling around.

I also plan on using headset mic(s) which IMHO are far superior to lav or boom for utilitarian instructional production. No, that is NOT the headset mic you see in my photo. That is an old, hard-wired production intercom headset.

[Richard Crowley]

Is this mixer dedicated to handling audio for your camcorder? Or is this mixer providing (for example) venue sound reinforcement, and you are taping into it for recording purposes?

You generally need to get from one of the line-level outputs from the mixer (XLR or TRS or RCA) and knock the audio level down to mic-level, and adapt it to the 3.5mm stereo mini-phone jack that goes into your camcorder.

The most straightforward way of doing this is to use an adapter box made for the specific purpose such as a BeachTek DXA-2 The current version is the DXA-2T (T for “tough”, they provide a rubber cover for the box to improve its ability to handle trauma in the field.)

Then you would use an cable appropriate for whichever output you are using from the mixer.

[Richard Crowley]

It doesn’t really matter exactly how far away the mic was. If the resulting audio signal contains such a high ratio of environmental noise, reverb, etc. then the combination is sub-optimal.

But there are a wide variety of factors at play. Such as expedience of production. For example if you are doing “run-n-gun” chasing a corrupt bureaucrat down the steps of the courthouse, there is a different expectation for audio quality. And “reality television” (which is anything but, IMHO) has somewhat changed audience expectations. Although, they go to rather extreme lengths to maintain broadcast audio quality with dozens of wireless body mics, etc.

[Richard Crowley]

Two feet away is NOT “fairly close” under ANY conditions. And especially in a small, reverberant room. Two feet is rather at the most extreme end of the working distance you could expect. I think you may have unrealistic expectations of what these microphones can do.

I fear you completely missed my question about the headset mic. My understanding is that the headset mic was on the interviewer who was off-camera. When you listen to JUST THE HEADSET MIC (without the hypercardioid mic on the subject), what is the signal-to-noise ratio and quality of the audio? Since the microphone is a few cm from the interviewer’s mouth, I would expect the track to be almost completely absent of the room/ambient problems.

Of course, we are assuming that you are recording the interviewer’s mic and the subject’s mic on separate tracks so you can isolate them and listen to them separately. If you are mixing the mics together during shooting, that is another practice you could avoid to help you deal with recording audio in a hostile environment.

[Richard Crowley]

It sounds distant and reverberant to me. The microphone is too far away from the subject for a room with those acoustics. And by acoustics, I mean BOTH the ambient noise AND the reflective surfaces (walls, ceiling, floor, table, whatever).

This sounds like a casual interview. Since you didn’t include the picture here, we have only the audio track as evidence, so you are privy to a great many more details here than you have disclosed to us.

What is the justification for using a microphone so far away on a boom out of the camera frame? I would challenge the producer on that one. What is more important here? NOT seeing the microphone (WHY?) or getting good sound?

Can you use a distant mic technique like you are using? Sure, in the proper acoustic environment (but that room isn’t it.)
Can you get decent sound in that room? Sure, with the proper mic technique (which is NOT a distant hyper, IMHO).

If you listen to JUST the sound from the off-camera interviewer’s headset mic, how is the signal (speech) to noise (HVAC sounds) ratio?

[Richard Crowley]

How many people are you trying to mic with a single hypercardioid?
It sounds to me like your basic microphone scheme is completely inappropriate for what you are trying to do.
A hypercardioid mic is appropriate for ONE person when you keep it aimed directly at their mouth.
A hypercardioid mic is NOT appropriate for picking up multiple subjects, ESPECIALLY if you are attempting to use it in a FIXED deployment.

Your expectations of covering multiple people in a noisy room with a distant, fixed hypercardioid is almost a text-book case of worst-case conditions.

The main problem here isn’t the air duct noises, it is the microphone deployment.

[Richard Crowley]

Software noise reduction is only a last-ditch method of salvaging otherwise useless dialog for something where quality is not important. It should NEVER EVER be used as as substitute for recording the audio properly to begin with. That includes selecting a quiet-enough location, selecting the proper microphone for the job, and positioning it at the proper distance form the subject.

Having to apply software noise-reduction in post production is an admission of major failure during production. IME, I categorically reject the very notion of trying to do this as a pre-planned part of any production. If audio is important, then select a location that is not audio-hostile.

If that categorizes me as hard-nosed and inflexible, then so be it. If the producer wants to compromise on the audio track, then they can find somebody else to do a marginal job.

[Richard Crowley]

Sorry, a recording of noise by itself is actually useless without the reference to the normal signal level.
Not clear why you would want to record in such a noisy room? Is audio not important to the production?
We hope that level ramp at the beginning is not an indication that you are using auto-level here?

[Richard Crowley]

Can you cover the HVAC grille during recording? Since you disclosed nothing about the room or the length of the recording shots/sessions, we have no idea whether that would be practical for you.

Or is the noise more low-frequency rumble conducted through the ceiling/walls and not coming out of the grille? If the noise if low frequency, then it is more practical to filter out with a low-cut (high-pass) filter. But broad-band noise (hiss, whooshing sounds, etc.) are impossible to FILTER because they are occuring at THE SAME frequency as the signal of interest (the speech).

Can you get the mic a lot closer to the subject(s?) Like use a mic(s) in front of the subject(s)? Or a headset mic on the subject? Proximity is your friend. The closer the mic is to the talent, the better the signal-to-noise ratio will be. And that includes ambient noise from HVAC. Again, since we know nothing of what you are shooting or why you are using an overhead boom, we don’t know how practical this would be for your situation.

Of course you can also look for a more quiet location to record, or cover the background noise with music or perhaps other options depending on what you are trying to do.

[Richard Crowley]

Many models are invisible except in extreme close-up shots.