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Avoiding Sound Hiss During Filming


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#1 Kirk Productions

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Posted 05 June 2006 - 06:25 AM

Hello,

Appreciate some help here. I am using a Canon XL1S Digital Video camera for an independant movie. I am using an external boom mic (because the stock one captures way too much) that records one channel (left). The sound is exceptionally clear, however when I am monitoring with headphones and the subsequent sound captures the "silence". Not sure how best to describe but when you are listening you can hear that sound of nothing in between lines....the hiss of having no sound.

Not sure that makes sense but I can't seem to get complete silence in between conversation lines. I know that if I mix with music, most will be hidden quite well but this has become a head ache.

Appreciate any sound advice.

PS: Also, is there a way to reduce this sound for existing footage?

Eric Kirk

Edited by Kirk Productions, 05 June 2006 - 06:26 AM.

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#2 Kirk Productions

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Posted 05 June 2006 - 10:13 AM

Hello all,

I've noticed quite a few reviews and no comments. Maybe I did not articulate my problem well. When I am recording, using that boom mic, I hear a lot of sound between people talking. Almost sounds windy because of the volume and record level of the mic. Is there a way to get complete silence, while recording voices well? What i do record is very very clear, it's just that "dead time" sound. The mic is an Audio Technica ATR55 Mic.

Thanks,
Eric

Hello,

Appreciate some help here. I am using a Canon XL1S Digital Video camera for an independant movie. I am using an external boom mic (because the stock one captures way too much) that records one channel (left). The sound is exceptionally clear, however when I am monitoring with headphones and the subsequent sound captures the "silence". Not sure how best to describe but when you are listening you can hear that sound of nothing in between lines....the hiss of having no sound.

Not sure that makes sense but I can't seem to get complete silence in between conversation lines. I know that if I mix with music, most will be hidden quite well but this has become a head ache.

Appreciate any sound advice.

PS: Also, is there a way to reduce this sound for existing footage?

Eric Kirk


Edited by Kirk Productions, 05 June 2006 - 10:15 AM.

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#3 Michael Collier

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Posted 05 June 2006 - 01:28 PM

well, first you gotta make sure the mic is as close as possible, and orientated well (a mic off axis may pic up less sound than a mic farther away, but orientated correctly) that way you reduce the ambient sound that gets recorded.

Next you want to make sure that the auto levels are switched off. When on they will boost the record level between lines, making the ambient sound rise as your actors stop talking.

after the fact there are a few things you can do to reduce the noise, but not much. Adding a parametric EQ can solve the problem. Usually if you take out the high end, and boost the mids a bit, a high pitch hiss can be eliminated. If its a hum or a steady clicking tone, a notch filter can reduce that. Keep in mind though that EQ is not a magic bullet. Its usually a balancing act between noise reduction and vocal clarity. Also I would hesitate to use any of the 'automatic noise reducers' I have gotten really weird results. Vocals that warble, music that doesnt sound right at all.

just remember that there is a ratio of voice to noise. Since generally you cannot reduce the noise in the room, the best you can do is make the vocal very strong, to overpower the noise.
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#4 Marco Leavitt

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Posted 05 June 2006 - 04:34 PM

There's a quite a lot of information online on how to get the best sound out of that camera. Many feel that if you use a mixer and go in through the line inputs (RCA), you'll get the best signal to noise ratio.

Check out this article at DV Mag, it's pretty much the definitive writeup on the audio performance of those cameras. (You'll need to sign up, but it's free and painless.)

http://www.dv.com/ne...ose_feature1102

I've had the best luck with that camera by splitting the audio track and recording one track about 6 db to 10 db lower than the other. Then you can keep the levels pretty hot with less worry about clipping. Basically, you want to maintain fairly hot, uniform levels with all digital camcorders. If you record too low, when you boost it in post you'll also raise all the hiss (noise floor) that has unfortunately been recorded to tape because of the fairly noisy preamps all of these cameras have. This is the main reason many people (myself included) still strongly urge double system sound if you have the crew to handle it.

Another tip: on any camcorder, try and keep the gain knob at about 1/3 of the way. Much lower and you'll get distortion, much higher and you get hiss. If you end up with levels that are too low using that setting, you have to find a way to boost the signal, like with a mixer. The Sennheiser ME series of microphones were specifically designed to accomplish this wihout a mixer, and have a very hot output. That's why they're so popular with no budget filmmakers. Most people feel that average peaks should hover (two or three times a sentence) at -12 dBFS to get the best signal to noise ratio.

Good luck.
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#5 Hal Smith

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Posted 05 June 2006 - 07:00 PM

A $49 mike is not going to be a very good mike - and one of the problems to expect is the built-in electret preamplier being noisy.

Rent one of the movie classics like a Sennheiser MKH416 for a day (make sure the rental house knows exactly what camera you're using and gives you the correct adapters, etc.) Take the 416 out for some test recordings on your camera and see what kind of results you get. I suspect you'll find the hiss is gone and the overall quality of your audio is much more lifelike - clean and transparent.
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#6 Michael Nash

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Posted 05 June 2006 - 10:05 PM

That hiss between lines is likely from the mic's "auto" gain. Switch the mic to "manual" and give it a listen under the same conditions.
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Aerial Filmworks

Paralinx LLC

Metropolis Post

Gamma Ray Digital Inc

Ritter Battery

FJS International, LLC

Wooden Camera

Rig Wheels Passport

The Slider

Opal

Media Blackout - Custom Cables and AKS

Technodolly

CineTape

rebotnix Technologies

Willys Widgets