How do you reduce audio noise?

[tomsemiterrific]

I've tried several microphones I own of different types. but the audio noise floor on my C300 Mk II is higher than it ought to be. 

Are there audio settings I can use to reduce the noise floor? The noise floor is lower and sound cleaner on my Canon XC15.

Any suggestions?

[Tim]

Hello tomsemiterrific, 

When you mention the noise floor is higher I take this to mean the base level of the audio without any additional sound inducing equipment attached?  

Are you measuring this in any scientific or observable way or just from experience?  

What type and style microphones are you using?  

If none are connected, is the sound floor more or less completely quiet?  

[tomsemiterrific]

I've used a variety of microphones, a Naumann shot gun, an Audio Technica lavalier connected by XLR, and a Sennheiser Shotgun. 
Let me ask you about sound levels.

I have always set the sound levels so the spoken voice will peak out about -10 to -6DB.

Perhaps I'm putting my recording levels to high for the C300 Mk II. 

I do  not seem to get nearly as much noise on the XC15.

[Tim]

 Hello tomsemiterrific, 

 Thank you for the additional information.  It sounds like you have tried multiple different microphones and for that we thank you.  

The peaking levels sound about right, do they tend to keep in the red just a little?  Probably don't want them spiking too much but on this we trust your judgement that they're accurate.  

If you lower the levels does the sound quality issue subside, get worse or stay about the same? 

[LarryCook]

I haven't used the c300 but I am a sound guy (well, used to be). Without the microphone plugged in, do you hear a hissing noise in your headphones? And, does it change as you adjust the input level? It should be very, very quiet, even if turned almost all the way up, without anything attached. If you hear a strong hiss noise without a cable attached, there is something worong.

[tomsemiterrific]

That sounds like...sound advice. thanks Larry. I'll check it out.

[Waddizzle]

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@tomsemiterrific wrote:

That sounds like...sound advice. thanks Larry. I'll check it out.

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Understand this, most audio level controls do not control how much you can amplify a signal.  They attenuate the amplified signal.  In other words, a volume control adjusts how much you can turn it down, not how much you can turn it up.

[tomsemiterrific]

After some time I'm still having this problem. I did disconnect everything and listen with ear phones and the line was quiet.

Next, I disconnected the Canon XLR audio and plugged in my Sound Devices Mix -Pre 3--I did some changes in the sound features of the camera, and that seemed to help. But loaded into FCPX the noise floor was still unacceptably loud and the analysis of the FCPX was "mixed"---the noise is simply unacceptable, even turning down the camera internals and boosting the sound with the Mix-Pre 3.

Any suggestions on what camera settings in the sound part I could check to turn down the sound?

I repeat, the XLR attachment on my XC15 is excellent--very quiet, very clean.

This is making me a little crazy.

[LarryCook]

Here's another check to run: Set your audio to XLR input, LINE LEVEL, with the audio input adjustment levels at 50% and RECORD for 20 seconds or so.

Next: Set the XLR input to MIC Level, and then RECORD for 20 seconds or so

In both cases, you should not hear hiss, or very, very low hiss. LINE LEVEL should be less hiss than MIC LEVEL - through your headphones, truned all the way up.

Bring that into the editor and see if the problem can be heard. If the answer is yes, then there is something wrong with the *recording* part of the system.

If the audio does not hiss in the editor, then the next test is your XLR cable, and next try a different microphone.

[Psychmark]

Shut off Monaural microphone and the buzzzzzzz goes away