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Super-clean audio - how do they do it?

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Daniel Stone
Super-clean audio - how do they do it?
on Jul 1, 2008 at 2:10:50 am

I'm watching the A&E show Intervention right now and I can't get over how there's absolutely no background noise in their audio tracks (fans, A/C, vents, etc.). How do they do this?

It's a run-and-gun reality show, so there's no way they turn off every single vent, fridge and A/C wherever they film. Whenever I do my own audio for an interview, I work very hard to make it as clean as possible - but there's always some sort of distracting background noise. I always capture room tone and have tried using SoundSoap to take it out but inevitably the sound I want to keep still gets colored.

Same thing in movies. How the heck do they capture audio that friggin clean?

I'm extremely picky about audio and will do just about anything to learn. Is there a DVD course or a book anybody would recommend?

Thanks so much!


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David Jones
Re: Super-clean audio - how do they do it?
on Jul 1, 2008 at 2:58:27 am

Well, there may be several reasons for this, but from a production stand point here are three:

One: they may have still turned stuff off like the AC, refridgerator, fans, etc.

Two: Low-cut filters! If you don't know how to use them, you need to learn. Low-cut filters (located on field mixers) will eliminate frequencies below a set frequency, like 120Hz, 140Hz. This will rid you of low frequencies like the ever popular 60Hz associated with AC units and the like...sounds you can't hear with your ears but will end up on your recording.

Three: using the right mics. Good boom mics like the Scheops MK-41 and Sennheiser MKH 60 (and others known as "true" condensers) will give you the best sound possible. Yes, they're expensive, but well worth it!

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Daniel Stone
Re: Super-clean audio - how do they do it?
on Jul 1, 2008 at 4:00:13 am

Hey David!

Good points!

I'm somewhat familiar with audio and the process, and low-cut filters are definitely "standard procedure" for me when recording/treating audio. I'm pretty well versed in types of mics, patterns, responses and uses.

Here are some examples of problems I've been having:

1. Filming in an office building: we have maintenance turn off the A/C on the entire floor which makes it quieter - but you can still hear air rushing through some sort of 'building ventilation' duct that doesn't turn off. 5 buildings and they all had this vent sound. Ugh!

2. In a house filming a short: we turn off the A/C, which makes the room nice and quiet. But now we can hear traffic outside.

3. Recording outside: traffic, locusts, people, sirens, birds! I watch movies that are filmed outside and the dialogue is beautifully clean. Not a single background sound other than artificially consistent ambience. Whenever I ask someone, the easy response is always "ADR" but I refuse to believe that every piece of outdoor dialogue in every movie is ADR. Then there's the issue of that phase effect (where the voice sound changes in relation to the position and distance of the mic from the source).

We recently rented an insanely expensive audio kit containing some Neumanns and a couple of Sennheisers -- thinking the better the mic the better the sound. They were definitely better sounding but they did nothing to reduce ambient noise. In fact, indoors, the nicer mics picked up more ambient noise... from air ducts to the building settling to the interviewee breathing.

Audio has definitely been frustrating to me and there's very little information on the internet aside from common sense suggestions. I'm starting to think that there's a well-guarded secret that only audio pros know.

I've discovered that making a beautiful picture is cake compared to capturing beautiful audio. I've also found that viewers will forgive poor lighting and even a blurry picture... but they will not forgive poor audio.

My hats off to sound guys!

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David Jones
Re: Super-clean audio - how do they do it?
on Jul 1, 2008 at 5:25:00 am

Hi Daniel-

My tips were just meant to be starting points to good audio (which you clearly already knew). And all those problems you listed, I've encountered as well. In fact, I read on another post that the post-sound facilty for the TV show "Lost", was complaining that they could hear traffic in the background from the dialog audio, when the show is suppose to take place on an island in the middle of no where! So even in Hollywood this sort of thing does happen. And another reality show on NBC had such bad audio, they had to "title" a lot of the stuff people were saying. Even good reality shows like "The Amazing Race" has some "titling".

Anyway, to your points:

1. Office buildings (in my opinion) are the worst! I was working on an inde feature one time, and on one paticular location in a bar, it took me forever to find all the sounds from "stuff" and turn them all off! One of the biggest offenders in offices, are computers. They actually make A LOT of noise.

2. Any house near traffic is a bad location for filming (at least for sound), there's nothing you can really do except shoot in a basement.

And you're right, good mics are going to hear EVERYTHING. Post-production can certianly fix some things, and mask others; hopefully someone else will post here with more answers on that :o)

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Bill Davis
Re: Super-clean audio - how do they do it?
on Jul 1, 2008 at 6:24:13 am

Another thing not mentioned here is to use the inverse square principal to your ADVANTAGE.

If you're using a boom mounted mic that's 4 feet away from the subject - and have an air vent that's 8 feet away (double the distance), there's just a 2 to 1 relationship between them, so the background sound will be just 4 times less than the speech you want to cleanly record.

A chest mounted lav (or better yet, a hair mounted micro lav) that's 6" to a foot from the mouth is going to increase the voice/background differential from 4 to 1 to a whopping 32 to 1 for the lav, or an even better 64 to 1 for the hair mounted lav.

And since you're moving the pickup closer, you can choose a LESS sensitive lav that will actually suppress MORE background sound relative to a highly sensitive mic in the same position. And really good lavs will also allow you to use low cut filters to diminish stuff like AC duct rumble even more.

It's not rocket science, it's just high school physics - but it's still unavoidable.

FCP since NAB 1999
creator: muti-track movies

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Steven Beers
Re: Super-clean audio - how do they do it?
on Jul 2, 2008 at 3:15:19 am

I have come up thru the audio industry and migrated my way over to the video side of things. I worked at a post production house in Boston, and learned a lot about workflow. Don't be so sure that on some movies they may ADR everything. We spent 3 days recording the telephone message system for Logan international airport. If someone has the time and money, they will do anything!

Lav mics are definitely the way to go. Boom mics are good, but they are going to always give you the problems that you talked about. Even the best mics will pick up room sounds around them. They don't know what they are supposed to be picking up, so they get anything that is in the vicinity. If done properly, they can be very natural, because that is how you hear things in real life. A lot of those "reality" shows use lav mics. You frequently see them on the characters' belts when they bend over. There are no deep dark secrets being hid from you, just a lot of experience by the engineers working through problems they see day in and day out.

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Dan Schaefer
Re: Super-clean audio - how do they do it?
on Aug 21, 2008 at 9:13:59 pm

Its also worth mentioning the many noise-reduction plugins that are used in post these days. The algorythms written these days for this purpose are amazingly effective and make production sound VERY clean with just a few tweaks and a click of a computer key...

I use them quite often, almost every day in post. Of course, we still PREFER to have the cleanest/highest quality audio possible coming in from the field, and I have never been a fan of the "we'll just fix it in post" attitude. I have a feeling there is probably some sort of noise reduction software involved in a lot of the reality shows nowadays.

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