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Noise reduction and Automixing in production


Jeff Wexler

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I would like to know how many have used noise reduction devices and/or automixing on the production track(s) and what the thoughts are on the appropriateness for production sound mixers to be using these things. A little later I will tell my own personal stories from the early 1970's when I used the Allison Research Gain Brain and Kepex, followed by the brief use of the Compex Limiter from Audio Design Recording (purchased in person at the factory in the UK).

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I had a Valley People "Dynamite" on my cart for many years, and used it to lightly expand and or lightly peak limit my mixes back when audio post for video was considered exotic and wasn't done much in my town.  I later made a "send-return" box for the Nagra IV-S (via the NR connections) to be able to go out to the Dynamite or a small portable equalizer or a different compressor when working without a mixer or a cart (like table-top portable).  They worked ok--these were situations where I had no confidence in the posties being able to deal with the BG issues.  As audio for video post became more common (lower barrier to entry, better gear etc) I gradually stopped doing this, and later cart remodels didn't include the signal processors.  Nowadays I don't do that kind of processing on location, other than using the built in peak limiters that most recorders have now--the tools for basic BG reduction and EQ are in all the NLEs and work well.   Re automixing, I rented Dan D's mixers for that when I needed them--worked great, but I'm still waiting to see if my current location sound "practice" ends up demanding automix in its current (like 688) form fairly often.  If it starts to I'll go for it, but it hasn't so far. 

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I have a gig next week with 3 or 4 actors in booths at a restaurant. No scripted dialog but I'm going to wire them up and test my Dugan 688 auto mixer. Seems like a valid test. You know actors are going to riff as they can't help themselves. Not even sure what to expect from the system but it seems like it might be useful if I understand what I've read about the technology. 

CrewC

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I used the mix assist feature in the 788T when it was implemented on a UFC interview, and it worked very well. That was the only time I used it on a mix track. Otherwise I used it a lot for IFB purposes when working on non scripted television, on a show with only two characters. Any other time I've tried using it, the machine doesn't want to let me because three or more channels seems to take too much processing power. 

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I used the 788 one just to clean the director's headphone when there is to many wirellesses. It is not usable on a mixtrack.

I use the 688's Dugan on a mix, on a talk show. I test it, and leave it on. 5 or 6 mics (4/5 handmics,1 headset, 1 stéréo mic) in noisy public places. It really helps me to provide a usable mix. 

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I use automix on occasion.  Usually for either panel discussions with multiple speakers, or live presentations with several people that need both a pa for an audience as well as recording for video.  I have also used the automix to reduce river noise shooting a dialog scene with 4 people, 2 of which were in the river.

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I only tried mix assist once with my 788T. I don't recall if it went to L or R track, but my mix and mix assist were both recorded.

In my scenario (4 actors with levels all over the place), I don't feel like the mix assist offered any advantage. I feel like I was able to follow the "mood" of the scene and anticipate levels better, rather than the mix assist which simply opens and closes the mic at the gain level set. For a large interview, or a scene with pretty consistent levels from many characters, I think the mix assist would be a great tool for the temp and director headphones. Perhaps it would allow better concentration on monitoring of ISO levels and such, which is really the most important thing on the narrative work I do. It is also a great idea to use mix assist on characters 7-12, or something like that, on a 2nd 788T. That output can feed into an open fader on the board. The mix assist becomes an ISO on track 8 of 1st machine, picking off lines from "extra" characters, with individual ISOs still recorded on 2nd machine. Those characters are dropped into your mix along with characters 1-6 by leaving the fader open. 

My fear of using NR or set, or even using SuperCMIT in some scenarios, is that a little knowledge is often a dangerous thing. My clients trust my judgement (at least I like to think they do). I do the best I possibly can to get a good s/n ratio in the environment they have chosen. If the background noise is terrible, and I deliver sound that is subsequently recovered in post, then everyone is happy. If I apply some sort of NR in the field, leading people to believe everything is ok, and they later discover under a controlled environment that it was worse than they thought, then that doesn't help me at all. Any NR applied on set will not help post. So there's really no scenario where using it on a narrative project with proper post offers any advantage.

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Sorry for double posting this link, but, relevant to this thread, and for those who might not have seen it, here is an article about the Dugan auto mixer now installed in the Sound Devices 688. Dan Dugan explains his auto mixer, and Jon Tatooles explains the difference between the Dugan auto mixer and the Sound Devices "Mix Assist", which is also installed in the 688. http://soundandpicture.com/2016/09/a-perfect-mix-sound-devices-and-dan-dugan/

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I recently tried the auto mix in my Nomad 10 on a group of four people wired in a large open space.  Wasn't terribly noisy or open sounding but since we were doing double system this was an ideal time to experiment.  Of course I had the isos pre fader so I wasn't too worried about the mix itself.  Also my son who was the DP was going to edit so I went for it.  I put the principle person on the left channel by herself, and the remaining three in auto mix on the right channel.  I thought it worked pretty well once I got the levels dialed in.  In my experience that's the key to these types of tools.   The gain staging still has to be right and soft talkers have to be boosted and the louder people brought down.  Its a nice way to bring down the overall background and minimize comb filtering in a larger group.

 

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With larger casts I sometimes let Mix Assist assist me in mixing. Great help if dialog goes back and forth (and around) quickly, I can leave some faders open for short bits and so on. Still it's me who decides how far up the fader goes. Also it's a nice helper when the 788T is in the trunk (I'm not. Never.) in "really driving" car scenes.

Setting input levels carefully is essential.

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  • 4 months later...

I have a 664 and thus no auto mixing.

I believe in delivering a mix but in complex situations iso tracks as well.

How does auto mixing sound if you have say a setup with 1 boom and 1 radio?

I had a situation recently where in dealing with two actors I used a boom and 1 radio.

I delivered this as a split track result (not mixed) and the post house questioned why I used

a boom and a radio, so are post houses now presuming that every actor wears a radio????

mike

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Many post production people assume that radios go on everyone, and we boom as well. On some shows (ad lib comedies, shows with three cameras all the time, unpredictable coverage, etc.) I wire everyone. It's the only way to protect me from the chaos. Normally I don't, and am often asked why. I tell post that I build relationships with actors, so if I need something from them, I can ask. Putting a wireless underneath clothing and invading personal space the second they walk on set, when not required, makes building that relationship harder. The post people understand when it's put that way.

I  have experimented with mix assist in some situations, but what it does is opens and closes a mic. It can't get a feel for how performances are going and adjust levels. 

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19 minutes ago, mikewest said:

How does auto mixing sound if you have say a setup with 1 boom and 1 radio?

I'd probably only have the radio on auto, so the boom's more natural background always is on. If I hear "phasing" from boom + lav, I can always turn one of them down manually.

As RPSharman just wrote, automixing can't adjust levels. That's why I think SD's term "Mix Assist" is better suited to production sound use. It saves me from having to exactly time when to open or close an actor's mic when that actor's un-rehearsed performance is different each take. I can concentrate on adjusting levels.

The more "proper" a shoot is going, the less lavs and the less automixing is needed.

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Nearly all the stories I hear about the use of mix assist or automix or whatever name is used for it start with the same sort of situation--kind of too many people talking in an undirected manner in a noisy location.  I see it as a thing to help you get through a bad day at the office--not something one would deploy unless one had to.  But, as a professional, you have usually have to play the cards production deals you, so having a tool handy to do so seems like a good idea.

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While I do agree that automixers can be a very helpful thing to get through a less than ideal situation, I don't think the speakers need to be that unpredictable for an automixer to help.  Any time you have a larger number of speakers, or very long sessions of speaking and automixer can be very helpful to make sure a word or two isn't missed accidentally, while also reducing feedback, reverb, and noise floor.  Panel discussions, or script table reads are a good example of a fairly controlled situations where automixers can really help.

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