Funky Audio

[John Foundas]

More often than not, I'm picking up a lot of background hum during my sit-down interviews. AC, room tone, etc... My lavs are properly placed but yet it continues. I'm monitoring the audio with good earpieces and I don't pick it up. It is only while in edit that it is prevalent. The apple/FCP audio effects don't really cure the illness. Is there a setting in the cam that I should look at? Hum/low-cut/high-cut function?

Im not well versed in Soundtrack to muddle through a post fix.

Any help would be greatly appreciated. Thanks!

 

[Jan_Crittenden]

If the hum is continuous and at the same all the way through, consider that it may be a grounding hum. This can be incurred by your audio lines intersecting the power lines, mixers not being grounded to the same AC as the recorders and/ or having your audio lies laid out in nice straight lines. Leave them coiled or at least slightly messy. They can act like antennas. Ballasts from Flourescent lights can also seem like they are silent but they can become noisy in a quiet scene, which an interview can be. Always use balanced mics, but some have transformers and others do not. Some locations play to the transformers

Hopefully this gets you thinking about the cause.

Best,

Jan

 

[Ed Kishel]

I find dimmers also introduce noise in mic lines.

I had no idea that laying XLR cables in straight lines could contribute to noise issues :shocked:

 

[little bobby]

They can act like antennas.

I've actually heard a radio station coming through a lav mic before during an interview. It was extremely faint, but I could hear it in my headphones. Luckily it was not apparent in the editing suite.

 

[Matt Gottshalk]

John, are you using AC power during these interviews?

 

[Multi-Media]

Hum can be introduced if the XLR cables are run paralell to AC power lines laid next to them... they should cross them at an acute angle. As far as post fixes go... a parametric EQ is the way to go... find the noise by boosting the slice and moving it up and down the signal to find the offending frequency (especially if it is a constant sound like a fridge) and then, after finding it pull it out to the point that it starts to make the voice over sound strange and then back it in 'till you're happy... or more or less happy with it. Sound Booth in CS5 has some pretty powerful tools to locate a specific noise and take it out.
The best approach is to kill the Air Conditioner for the few minutes you're recording or on and off for takes.