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Old January 17th, 2004, 07:14 AM   #1
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Ambient Noise on Recording

Hi:

I have read many of the posts related to noise issues and still can't figure out what to do about my problem:

I own an XL-1 with MA-100 and Lightwave mic mount.

If I record in a silent room, I get noticeable ambient noise during recording. This problem persists whether I:

* detach the MA-100 and just use the Canon on-board mic.
* detach the on-board mic and use a Sony XLR lav w/MA-100

The ambient noise is not motor or lens noise. If I hand-hold the on board mic (eliminating motor noise completely) I still pick up ambient noise.

I am recording in 16-bit. When I toggle to "auto" it's so bad I really can't believe that it's "normal." When I toggle to manual, I can reduce the noise (or increase it) by adjusting the level knob.

I called Canon Repair Facility and all they say is send it in for an evaluation, and that "repairs" range from $250 - $400. My question is, am I expecting too much to want absolute noiseless recording in a silent room? Has anyone heard that Canon has a "fix" for this problem? The camera was purchased in 1998.

Many thanks.
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Old January 17th, 2004, 08:23 AM   #2
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No such thing as absolutely silence in most rooms, even anechoic chambers have a noise level.

But more important - all condensor mics have a nosie floor (self noise from internal electronics) and moderate priced condensor mics (e.g., the Canon build-in mic) will have higher noise floors than costly profesional mics.

As an additional test you could try record with NO mic connected to evaluate the baseline noise floor of your XL1's internal circuits (expect on the order of 60 dB below maximum record level for the MIC setting). Noise above that is self-noise of the microphones and ambient noise picked up by the mic. The XL1 self-noise will be highest in MIC setting, lower at MIC ATT setting, and lowest if using Line input level, and will increase somewhat as the lvel controls are increased.

Toggle to 'auto' turns on the AGC, which increases the XL1 gain to the max in an attempt to bring the recorded sound level (which in your tests is mainly noise from all sources in a quiet room) to normal record level.

The point of course is to have the recorded noise floor as low as possible relative to the wanted sound. You should be able to obtain noise floor improvement in your recordings by using a high quality external mic preamps or mixer (not cheap), high quality microphones (none of the under $400 stuff) and sending a line level (-11 dBV) signal to the XL1 Audio1 input. If you need better than that gives you, you will probably need to move to professional audio recording gear (e.g., DAT).

Another apprach is to apply a noise gate to the audio in post production to remove/reduce noise during generally silent portions of the program material. But sound recordings with no noise what so ever may sound a bit unnatural. After all, we live in a noisy world.
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Old January 17th, 2004, 08:47 AM   #3
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Thanks very much for your reply. I did follow up with your advice, and recorded with no mic attached.

On playback on a Sony DSR-80 DV Deck, the meter reads one bar over -60db. And, through headphones coupled via the deck's headphone jack, sounds like an ocean of static. Normal?
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Old January 18th, 2004, 07:13 AM   #4
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Sounds about normal. Headphones tightly couple ALL sound to the ear, and will tend to emphasize any sound (program or noise) present. If you have normal program material recorded so sound peaks are close to 0 dB, and you are listening at levels somewhere below the threshold of pain and rapid hearing damage, the -60 dB noise level will be inobtrusive to most listeners - it is better than FM radio or TV broadcast.

Again, if you need lower noise, use an high quality external preamp and line input level to potentially gain ~10 dB of noise floor, or switch to higher end audio recording gear.

Note: probably better to judge the actual noise level from the audio stream captured via firewire and then opened in an audio editor tah can gather statistics on the stream. I don't know the DSR-80, but at -60 dB most VTR/deck metering is at the low limits of usibility, being mainly for judging audio as it gets in to the -12 to 0 dB range.
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