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Old September 20th, 2002, 12:35 AM   #1
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Audio options in noisy places

Greetings DV Community,

HELP! What's the best way to block out very noisy ambient sound, such as machinery in a manufacturing plant, for worker training vids I'm trying to create? I've just recently invested in the XL1-S after dabbling occassionally with the VX1000. Anyway, do I need to go with a boom / shotgun mic? I've pinned an XLR lapel mic on my spokespersons, via the MA-200 Adapter on my XL1-S, but can't seem to get the background noise out. (The mfg. plant runs 3 shifts 'round the clock, so the noise is a given.) The "attenuator" feature of the XL1-S doesn't seem to be available on the menu when selecting the XLR inputs. If I choose to use the camera mic and the attenuator feature, both the ambient sound and the spokesperson are muffled. Am I doing something basically wrong? HELP!
Joe Angelitis, Bath, Pennsylvania, USA
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Old September 20th, 2002, 01:02 AM   #2
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Welcome, Joe!

Glad to have you aboard.

Well, the answer is that it's just darn hard. Getting good sound in the field is akin to doing an electrical experiment underwater. Once you've done everything possible to separate your subject from the noise the rest is up to your mic strategy. Sometimes a -unidirectional- lav can produce good results. (Note that most lav mics are omnidirectional with medium fields and will pick-up nearly all surrounding sound.) Otherwise you're probably looking at using a boom-mounted shotgun mic with a very narrow field positioned very close to the subject. And remember to always point that shotgun downward to avoid picking up sources behind the subject. I've heard of crews using acoustical foam mounted to foam-core board to absorb sound from the sides of a subject but that might be extreme for you.

Either way, it's doubtful that you'll get good results from the on-cam mic which is omnidirectional and designed to pick up fleas breaking wind at 20 feet (or so it sounds sometimes). The attenuation circuit will not be very helpful in this circumstance (as you've already discovered). It seems designed mainly to control very loud sound from primary sources (ex: shooting a Harrier jet at close range). It will make voices sound like a kidnapper's ransom request phone call.
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Old September 20th, 2002, 01:45 AM   #3
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Thanks Ken!

In addition to validating some of my newbie conclusions, and making me feel less at fault for the hum of machinery competing with my spokesperson's voice, you made me laugh at least four times. Volume range controls should have an icon of a flea's behind at one end and a Harrier Jet at the other!
OK, then, if isolating the speaker during video capture is that challenging, is there a best practice so that's it's easier to isolate the speaker's voice during the editing process (e.g. in Adobe Premiere 6.0) by choosing certain audio settings on the camera? I apologize for the broadness of my questions.

Joe Angelitis, just North of Allentown, PA
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Old September 20th, 2002, 02:11 AM   #4
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Your ability to isolate the subject's voice from background noise in post-production will depend on the nature of the background noise. If it's predominantly above or below the frequency range of speech you might be able to apply various audio suppression filters without damaging the speaker.

But if it's an extremely loud environment (as evidenced by everyone else wearing OSHA-grade ear protection except YOU) or the frequencies of the background noise is all over the spectrum you'll have little luck with filters. In this case your best tack may be to change your shooting strategy. If you're doing a plant walk-through-style narrative I'd recommend shooting your interview separately in a quiet, controlled environment. Then shoot the walk-through separately. You would then weave the two together with Premiere by using the interview as voice-over to the walk-through, perhaps cutting away to the interview video as occasional b-roll footage. During walk-through shots you'd pull it's sound down to a background level (for a sense of presence) behind the interview audio.

Hope this helps you. Good luck (and get some good foam ear plugs)!
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Old September 20th, 2002, 07:42 AM   #5
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Voice over/lip synch in post. Use the camera sound from the factory floor for background.

If only voice, would noise cancelling mics such as found on some head sets for aviation use work?

Maybe the high noise level is part of the story.
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Old September 20th, 2002, 05:39 PM   #6
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Thank you for your feedback Ken and Don.

My experience today with the XL1-S on the noisy factory floor:

Visually, it was a vast improvement over lens limitations I experienced with the VX1000, but unfortunately I definitely went backwards regarding the audio.

By the way, what I'm doing is a training piece on production set-up of particular machinery, so I'm zooming in close on thumbscrews, setscrews, cams, etc., and having their personnel show steps 1,2,3,4... (What is motivational for me for such content is the fact that I am helping the new hires to learn the machinery set-up process according to recommended procedures, and they get to SEE IT rather than read a text manual, and it's a better orientation than the old school style of being tossed out onto the floor to learn haphazardly with some cranky lifer named Harry.)

I did a similiar piece for this company (different building and different machinery) previously using the Sony VX1000, but I wasn't able to focus in close on small parts, so that's part of the reason I went with a Canon and their reputation for lenses/photography, and that side of things worked out well today.

However, the cheaper audio set-up I had before ($180 Azden wireless lav mic on the VX1000) was much better than anything I tried today with the XLR wireless. Perhaps the Azden wireless I had was uni-directional (the transmitter has since been swiped from stage at a night club shoot), or perhaps just a different frequency. Anyway, today with the XLR it sounded like I was INSIDE the surrounding machinery. It was as though the XLR lav mic was on the same frequency as the ambient noise and amplifying the noise more than the spokesperson's voice. It was horrendous anyway I selected it.

Voice-over narration is my only option for the nice bright shots I got today, so I'll have to learn how to do that. I think I will get a replacement Azden transmitter and experiment with it in the RCA jacks of the XL1-S ( ? )

Ken, your advice last night/ this morning, regarding how much of a challenge it is to separate noise during capture, saved me today from being hot under the collar thinking I was just not pushing the right buttons.

Thanks again!
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Old September 21st, 2002, 07:38 AM   #7
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Joe

If yohave a few minutes to research, visit the Shure website and read some of their tech papers on mics. helps understand some of the issues. Part of the answer is to get the mic as close as possible to the talent so the talent voise is far and away the loudest sound reaching the mic.

Consider vocals anda band on a stage of sound. The singer is just about swallowing the mic, whihc allows the voice to drownd ou tthe other sources.u
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