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Repairing/homogenizing audio recorded at different distances (and other issues...)

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Terry Nutkins
Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 1, 2014 at 11:59:58 pm
Last Edited By Terry Nutkins on Dec 2, 2014 at 12:01:10 am

Hi there,

I have been recording audio for a documentary (which mostly comprises seated interviews) with a hypercardiod (Sennheiser MKH 50).

Initially, the mic was always placed just outside of frame (approximately 12”) and the results were what I had hoped for and without problems.

However, on the last major production trip, in part because I decided that we needed more flexibility in terms of framing the interviews (in order to employ wider shots when desired), the mic was placed further from the subjects - roughly 16-20”+ from the source, as opposed to the seemingly ideal 12” placement that was used initially.

Sadly the resultant audio is almost always inferior to the original material and I have been regretting sacrificing the sound quality to allow for wider framings. With a few exceptions, I am hoping that ultimately it does not appear to be a colossal loss in quality, but it is certainly less than perfect – primarily due to loss of bass and presence; coloration; and the room being more apparent. Additionally there are a few instances where the subject leans forward substantially, thus going noticeably off-axis.

At this stage I am wondering to what extent the inferior audio can be treated so that it can seamlessly match the audio where the mic was placed 4-8” closer.

I have (with my own cursory knowledge of processing) attempted to rectify it myself and have managed to get it so that it may possibly be almost unnoticeable to the untrained ear, in some cases. Ultimately though I am wondering what the prognosis is in terms of how well it can be repaired when it is eventually processed to a high standard by a post-production audio specialist, as it will be professionally mixed when the final cut is complete.

Re-shooting everything affected would be very expensive and impossible in some cases, so that is definitely a last resort.

If it makes any difference, background music will be running through almost all of the film so I am hoping that this will further help to mask any differences.

Please find attached some examples of the (completely untreated) audio...

http://www.filedropper.com/examples_7

Example 1: Comparison of 12" placements with greater distances (the sequence of which is 12" then greater, 12" then greater etc - last example is particularly noisy)

Example 2: Audio of the same subject in a different room - 12" distance first, then greater.

Example 3: Heavy room noise (the worst example of this - any hope for this being fixed??)

Example 4: Subject going on then off-axis (the difference was much more noticeable when EQ was added).

Example 5: Very loud high-pitched hum that goes through parts of the interview (perhaps this is too severe to fix?)

Any thoughts are hugely appreciated.

Thanks!


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Peter Groom
Re: Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 2, 2014 at 8:29:05 am

Its not really possible to deecrease room tone. But you can add refelections to a tight recording to degrade it to match the other? Not ideal but thats your choice.
The samples you posted.
Izotope will learn and remove a lot of the heavy room rumble anfd the high pitched whine on 2 or the recordings.

This is why id personally always use a personal mic which can be hidden "in shot" on 1 track and 1 boom mic as you have just out of shot, so when the shot size changes you still have close audio.
Id also investegae a rifle with a longer and sharper reach than your rifle so you can get better distance, but that doesnt help you right now on this recording.
Have a look at Isotope rx.
Peter

Post Production Dubbing Mixer


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Bruce Watson
Re: Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 2, 2014 at 5:51:04 pm

[Terry Nutkins] "I am hoping that ultimately it does not appear to be a colossal loss in quality, but it is certainly less than perfect – primarily due to loss of bass and presence; coloration; and the room being more apparent. Additionally there are a few instances where the subject leans forward substantially, thus going noticeably off-axis."

It should not be a "colossal loss in quality" since this particular mic is popular for dialog work in Hollywood, and they often record in the 45-60cm range. If you've been to movies, you've heard plenty of dialog recorded at 45-60cm and further out. I would consider this to be more "normal" than your work around 30cm. Indeed, recording so close as you did resulted in very noticeable proximity effect, some high frequency boost due to being so close, and a loss of room tone. This isn't necessarily good; many post people would consider it bad (because it's more stuff they have to fix).

[Terry Nutkins] "At this stage I am wondering to what extent the inferior audio can be treated so that it can seamlessly match the audio where the mic was placed 4-8” closer."

Consider the reverse instead. That is, instead of wondering how to boost the bottom end and the presence region of your more distant recordings, you might want to consider reducing the bottom end and presence region of your close recordings. It's much easier to add some skillfully designed reverb to your close recordings than it is to try to remove room tone from your more distant recordings. And remember that every room is different -- room tone is not supposed to match from room to room. So when you cut from scene to scene, it's expected that room tone will be different across the cuts.


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Ty Ford
Re: Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 2, 2014 at 9:28:49 pm

Hello Terry and welcome to the Cow Audio Forum.

You may be able to reduce some of the room ring from the tragically recorded piece (engage humor filter, please) by using DeVerb in iZotope RX3 or RX3 advanced. If you care to, please post a 20 second or so sample and I'll give it a whack.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Peter Groom
Re: Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 3, 2014 at 8:40:12 am

Hi Ty
How do you find de verb when used in anger?
I often find it goes a bit watery before enough removal?
Peter

Post Production Dubbing Mixer


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Ty Ford
Re: Repairing/homogenizing audio recorded at different distances (and other issues...)
on Dec 3, 2014 at 12:28:58 pm

Peter,

Quite right. I don't think it's ever made the audio "as good as new", but it has made the unusable usable.

The results do vary even on samples that seem to be similar and I'm not sure why. I suppose it has something to do with the way the algorithm works.

I've tried several other software solutions and found about the same.

One of the things RX3 does well is remove the nasty envelope of distortion around some cell phone calls. The audio still sounds like a cell phone, but it's much less annoying.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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