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Old May 25th, 2008, 01:56 PM   #1
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Audio Woes

Hi, I've just come back from a weekend of filming only to discover the audio I recorded on my XL2 is nothing short of awful. I was using a tie clip-on mic using the front mic connection and not only did the microphone pic up a horrible amount of noise, it was also very quiet.

Here's a link to an 11-second sample:

http://www.bakersvideo.com/noise.mp3

I can get the noise down by switching the "att" switch to ATT but then it hardly records any audio at all so that's no good. This noise doesn't sound like the mechanical noise that the camera makes - and as the mic was directly under the speaker's chin it wouldn't have picked that up anyway.

The dials to channels 1 & 2 were set to 3/4 of the way to Max value. Even if I use the front mic that came with the camera it still pics up the same amount of noise.

Have I done something wrong or is the camera defective? I just find it impossible to believe that a camera as expensive and as good as the XL2 cannot record audio better than the rubbish I have got!

I have audition 1.5 and I am able to clean up the audio to a certain extent using noise reduction although the voice sounds a little tinny.

Any advice with this would be most greatfully appreciated as I have another video shoot next weekend.
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Old May 25th, 2008, 03:20 PM   #2
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Hi Adrian.............

First lesson with audio:

Listen to what's going onto tape, as it goes. It's too late after.

Without knowing the circumstances of the taking of that clip, what I can hear (apart from the monologue) is:

Some pretty rampant 50 Hz hum from???

(possibles: fridge, AC unit, flouros, motor, loose connection, etc etc).

Some pretty nasty mid/ high frequency "bounce" from????

(possibles: hard walls, floor, ceilings, other objects).

Bottom line is this. The microphone, camera combination doesn't hear like you do. It has no inbuilt filter to automatically remove the junk your brain does in the same sound gathering circumstance.

Your only protection is a good set of closed back cans parked over your ears with the sound cranked up nice and high so you hear what the microphone does - then figure out how to eliminate the junk there and then.

Turn everything electrical off, deaden hard surfaces with a rug or carpet etc etc etc.

The reason both sets of mic's picked up the same amount of junk was that the junk was there, but you didn't hear it because your brain filtered it out as "junk" (and you weren't listening specifically for it).

Don't think you can blame the equipment for this one, think of it as "operator error".

Of course, if you were monitoring the sound and that wasn't what you heard as it was going to tape, then you do, indeed, have an issue with the equipment.


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Old May 25th, 2008, 06:10 PM   #3
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This has been said before, many times: monitor your audio while recording with headphones. While some flaws can be reduced or eliminated in post, generally speaking, what you've recorded is all you're going to get. Period.

Is this the first time you've used that particular mic? Any special reason you decided to use an external mic? I've done most of my documentary work with the stock XL2 mic, letting the autolevel control the gain, and have been pleased with the results.

My suggestion is is to get a mic with balanced output and use the 3-pin XLR connectors at the rear. MUCH less electrical noise.

Check your particular setup BEFORE going out on a shoot. Do you still get noise from the stock XL2 mic when shooting in the middle of an open field? Try it with your clip-on mic. If the sound is clean away from any noise sources, then it's something in the shooting environment that caused your earlier problems.

Buy a set of headphones and use them. Seriously. They don't have to be expensive, but try for a good pair of over-the-ear style if you can afford them. I use Sony MDR-7506 headphones, $99 USD. Over-the-ear headphones help shut out the room noise and let you concentrate on what the camera hears. But even a light set of walkman-style headphones are better than nothing.

ETA: took another listen to your sample. 50hz interference, I'd say, probably "leaking" in through an unbalanced microphone line. Were there any florescent lights nearby? Look for a balanced microphone and use the XLR inputs. They inherently block electrical noise.

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Old May 26th, 2008, 03:39 AM   #4
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Many thanks for your replies.

I had to use several lights in the scene because I was using a green screen so it had to be well lit. Unfortunately the room we filmed in was very small (I didn't know how small it was going to be until I got there).

This is probably going to make me sound stupid but I did use headphones whilst recording (over the ear type), and yes I did hear the horrible hum but whatever I tried I couldn't get rid of it so I had to carry on with what I could get.

The reason I used that microphone was because there were loads of external noises coming from outside (banging etc) so using the on-board mic would've picked up those sounds much more readily than the tie clip-on one. It was the first time I had used it, yes.

I am quite happy to blame me as long as I know I can get around this for future shoots! So I will try your suggestions (ie filming away from any "junk") and see what happens. I have to say my first instinct was the damn mic connection causing the hum but that's just a guess.
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Old May 26th, 2008, 03:47 AM   #5
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I meant to ask in my last post:

"Look for a balanced microphone and use the XLR inputs. They inherently block electrical noise."

Any suggestions on make/model of microphone I should go for? When you say "balanced" microphone what exactly do you mean?

Thanks again.
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Old May 26th, 2008, 05:39 AM   #6
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Hi again...........

The "balanced" mentioned is actually a cableing/ connection type.

A "standard" microphone connection has a "live" and a "ground" connector in the cable.

Any electro magnetic interference hits both, but the one that hits the "ground" is shunted straight there, leaving the "live" to carry the can.

A "balanced" connection has two "live" and a ground. The difference between the two "live" is what is taken into account in the following stages.

It matters not (within limits) what crud hits the three conductors:

The ground simply shunts it to ground.

The following circuits only take into account the "difference" between one live conductor and another.

Thus EMI (electro magnetic interference) is far more easily avoided.

Seems I was right. Small room etc.

If you could hear it, well, there you go.

Going "off camera" seems to have been the best choice out of a lot of bad ones.

Future?

Get a balanced mic and cable system (yes, the cables are different) and don't shoot if the cans say it's a slow motion audio train wreck in progress.


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Old May 26th, 2008, 12:21 PM   #7
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Well.... I tried the mic in an open space with no other sounds (apart from birds)... same amount of noise picked up.

I tried the XL2 mic and whilst that still picked up a little noise it was much less than when I was shooting at the weekend.

So that points to a rubbish microphone and a rubbish location to shoot in. Apart from those two things I would have ended up with perfect audio!

I'll do some googling re: balanced microphones.

Thanks a lot for the info :-)
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Old May 26th, 2008, 12:46 PM   #8
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Chris covered the technical side of what a balanced microphone is. For the most part, just consider them "magically interference-free." :)

These are my suggestions. Take 'em with a grain of salt. They work for ME, but not necessarily for what you're doing.

Best local microphone hunting is at a musician's store, back in their pro audio section. Mics come in two basic flavors (there are more, but let's keep things simple) -- dynamic and condenser. I usually go with condenser mics because they have better sensitivity. They also have to be powered, either through a battery in the mic itself, or by what's called phantom power provided by the recording equipment. Your XL2 provides 48 volt phantom power when you throw the right switch on the back. If your mic has a battery, leave the phantom power off.

Mics have different pickup patterns. Omni (or omnidirectional) mics pretty much pick up all the sound around them. Cardioid mics tend to pick up what's in front of them and (mostly) ignore what's behind them. Hypercardioid and supercardioid mics are even more focused, "looking" at an even narrower range of what's in front of them. You also have to pay attention to what's directly behind them, as they have a "spike" in their pickup pattern directly to the rear. Shotgun mics are even tighter, but they don't work indoors too well due to reflections off walls.

My suggestion is that you get a medium-quality cardioid condenser mic. They're common enough and work well to kill noise from the backside. You can do about 80% of dialog recording with one and not have to keep shifting to keep the mic pointed at the talent.

As for a specific mic recommendation,there are others who can help better than I. I use a pair of Audio Technical AT2020 mics on stands for live recording bar bands. They're larger than most hand-held mics, and you talk to them from the side, rather than directly into the top like most mics, which can confuse some people. You can't really hide them, so sometimes you have to get creative to keep them out of frame, but they put out a strong signal, so close works well.

Martin
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Old May 28th, 2008, 10:43 AM   #9
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Great post Martin thanks for that. I've found a place in the UK where I can buy one of those mics you talk about.

In terms of noise reduction, is Audition 2.0 or 3.0 any better at this than version 1.5?I'm just wondering whether it's worth upgrading or should I just write this off and put down as a learning experience? That said this has certainly been a learning experience!
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Old May 28th, 2008, 03:12 PM   #10
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In some cases, depending upon many variables, some noisy audio can be somewhat salvageable, with diligent application of the right tools. (As noted in the other posts, though, nothing beats proper recording and monitoring technique.

In the case of the noisy mp3 you posted, attached here is a slightly cleaned up version from running it through an audio scrubbing application. This was done in one quick pass without any tweaking, so with some additional work it could even be better, and then it could be improved even more with some proper tonal balance- which I did not do. I just wanted to see how much noise would be cut out through a quick pass. Such an effort might be able to salvage the audio from your project.

-Jon
Attached Files
File Type: wav noisesinglepass.wav (127.7 KB, 70 views)
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Last edited by Jonathan Jones; May 28th, 2008 at 06:31 PM.
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Old May 28th, 2008, 05:58 PM   #11
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Quote:
Originally Posted by Adrian Baker View Post
In terms of noise reduction, is Audition 2.0 or 3.0 any better at this than version 1.5?I'm just wondering whether it's worth upgrading or should I just write this off and put down as a learning experience? That said this has certainly been a learning experience!
Can't tell you. I'm cheap. I use Audacity. It's free. Plus I spend a lot of time making sure I get as clean an audio track as I can beforehand, so I rarely (if ever) do much in post other than tweak levels. Last thing I can recall doing is running a track through a "telephone" filter to make one important line understandable against a noisy kitchen background for a documentary. Someone was chopping dates nearby.

Martin
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Old May 29th, 2008, 04:55 AM   #12
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That's pretty good Jonathan - which app did you use to do that?

I've managed to clean up the audio somewhat using Audition, but the voice is now somewhat "tinny". Here's the clip (together with quick green screen keying):

http://www.bakersvideo.com/HypnosisFinal.wmv

Believe me I'm not happy with the audio but I can't think of any way to get it better than this using Audition 1.5.

As this is only meant for a web video I'm hoping the audio will be passable for this medium - obviously for DVDs it's nowhere near good enough.

I have well and truly learnt my lesson though that good audio at source is essential.
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Old May 29th, 2008, 06:56 AM   #13
 
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I don't hear any problems with the sound except for one... The hiss on words with "S" and "C". That is really annoying, more so than what you originally described.

Just one person's opinion.
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Old May 30th, 2008, 12:19 AM   #14
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That's pretty good Jonathan - which app did you use to do that?
I ran it through a quick pass in Soundsoap 2. As I mentioned, I didn't do any tweaking with it, but if I had, I am sure it would have been even more improved. Subsequently, I would then recommend putting it through some additional processing to fatten it up a little bit and reduce some of the over-modulated sibilance.

-Jon
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Old May 30th, 2008, 06:24 AM   #15
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I like the sound (excuse the pun!) of the Soundsoap 2 software Jonathan. I've never actually used additional software to get rid of bad backround hiss etc in my previous movies, as I've always tried to obtain the best and cleanest sounds possible during the actual original sound recording; but this is of course not always possible in gun-n-run situations, or when you are filming on very windy days (does the Soap 2 help in any way to get rid of some background wind-hiss as well?).

http://www.lafcpug.org/reviews/revie...dsoap_pro.html

I've also looked at the new Soap Pro (an advanced version of Soap 2), but it comes at four times the price (and double that again at UK prices) of Soundsoap 2. Have you worked with the Soundsoap Pro version, or do you think the Soap 2 is enough for most applications?
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