Some help with Noise Removal?

Audacity 3 Help Forum macOS
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Hey everyone—

My problem isn’t really related to my OS or Audacity functioning incorrectly, but I’ll follow the format in case I’m wrong about that:

I am running Mac OS X 10.9 (Mavericks), with Audacity 2.0.3 installed. I think I installed it from the DMG, but it was a long time ago, so I don’t remember. Either way, it’s on my hard drive, not running off a mounted DMG or something like that.

Anyway, here’s my issue: I use a shotgun mic mounted on a boom pole and plugged into a Sony audio recorder for recording external audio when I shoot videos with my DSLR. The mic I have is fairly old, and it was made to sit in a hot shoe, plugged into a DV-tape camcorder using a 3.5mm audio jack. So it’s not exactly a Rode XLR shotgun mic, but it’s miles ahead of the onboard mic on my DSLR. The recorder is a Sony ICD-AX412 (link).

When I shoot, I make sure to set the gain on the recorder as loud as I can without clipping, and hold the mic as close to the subject’s mouth as possible. I also make it a point to record 30 seconds of “blank” audio to get a really good sample of background noise to use in my Noise Removal cleanup in post production.

The problem I’m finding is that depending on the amount of Noise Removal I apply in audacity, I either cut all the hissing and unwanted background noise—ending up with dialogue that sounds tinny and weird, or I have to leave some hissing in to get the dialogue to sound normal. I can’t seem to find a middle ground. Even in a very, very quiet environment (i.e. no cars driving by in the background, no real ambient noises that the shotgun mic is picking up; just the standard hissing that my mic seems to generate), and using a perfect 30-second sample of blank audio to source my background noise, I can’t seem to find the right balance.

Any tips here? I don’t want to blame it on my equipment… it seems like my signal-to-noise ratio is just somewhere it shouldn’t be and I would like to believe I can fix that by improving my technique instead of having to upgrade my gear.

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I’m going to have to sit down for a minute. Few people get so many things right in one posting.

The mic I have is fairly old, and it was made to sit in a hot shoe, plugged into a DV-tape camcorder using a 3.5mm audio jack.

First problem. XLR microphones are very carefully matched to their preamplifiers to get the absolutely best quality sound along with the lowest possible hiss/noise. Anything you do other than that is going to cause problems. Microphones create sound signals down in the molecular noise level of semiconductors, so this problem isn’t trivial and everybody has to address it. I designed and build a “perfect” MicPre following all the noise and quality design rules as an exercise. It’s the size of a loaf of bread and weighs as much as a quart of milk.

But it does run. One of the guys at work used it (slowly) for a project at a local university. He said the only reason he stopped using it was the project concluded. It was perfectly well behaved and quiet.

When I shoot, I make sure to set the gain on the recorder as loud as I can without clipping, and hold the mic as close to the subject’s mouth as possible. I also make it a point to record 30 seconds of “blank” audio to get a really good sample of background noise to use in my Noise Removal cleanup in post production.

Absolutely correct, but please know that “Room Tone” (idle sound) is only going to be valuable if the noise is specific and periodic. It doesn’t work with traffic noises, busses driving by or jets going over. It also doesn’t work with rain-in-the-trees hiss, white noise or other broad-band noises. It only works with air conditioning rumble, fan noises or other noises that do not change over time.

Noise Reduction works by generating a filter based on a sample of the noise (the Profile step) and then tries to remove that exact, specific noise from the show. If the noise changes between the profile and the removal, it will fail.

Hiss or white noise fails because Noise Reduction tries to create a filter that removes the whole show. I’m not making that up. Hiss is trash at all frequencies including the ones people use to talk.

just the standard hissing that my mic seems to generate

As above, you can’t remove hiss, and it’s not just the microphone. It’s the marriage between the microphone and the first amplifier it’s plugged into – the Microphone Preamplifier or MicPre. That’s why mixer makers push the fact that their equipment has “Patented Zootropic, HooHaa, World-Beater, Hollywood MicPres” inside. Whatever. It usually doesn’t mean anything, but they know that you’re supposed to be watching that specification. That part is perfectly true. Any low impedance, balanced microphone is going to work better, quieter than what you got.

When you shoot video, you make do with a chemically-fogged, scratched, beat up lens on the camera, right? No?

A video with no picture is a radio show. A video with bad sound is a rehearsal.

This is me cleaning up after a shoot.

A Shure FP33 field mixer has legendary quiet MicPres. This mixer is half dead and I still use it for mono sound shoots.

Koz

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I was eating lunch and I passed a “Pro-Looking” video crew also having lunch (three people looking serious). I asked which microphone was inside that wind sock and the techie said it was a Sennheiser 416.

http://www.sweetwater.com/store/detail/MKH416?utm_source=Google&utm_medium=PPC&utm_campaign=recording&device=c&network=g&matchtype=&gclid=CNKY3u6127sCFc9sfgodnR8Atg

There’s another trick. Nobody I know records field sound below 100Hz. Always throw the 80Hz, or 100Hz high pass filter in before you record. Nothing valuable ever happens below that. If you don’t have one, you can buy one.

http://www.shure.com/americas/products/accessories/microphones/microphone-problem-solvers/a15hp-inline-high-pass-filter

It works on most XLR microphones.

Koz

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And my mic isn’t even XLR, it just uses a 3.5mm audio jack. I knew that such a setup had a higher signal/noise ratio than an XLR mic (which would, if I understand correctly, explain the noticeable hiss), but I didn’t realize that the hiss was something that could not be fully cleaned without damaging the quality of audio even in the dialog. So it’s starting to sound like I may have hit the ceiling of quality that I can achieve with my current gear… is there anything else you can think of that would help me get better quality (whether in recording or in post-production) with my current setup?

Otherwise… I started speccing out some alternative setups for the audio half of my double system. I’m looking at a Rode NTG-1 and a Zoom H4n. Thoughts? Suggestions? Recommendations?