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Need help identifying noise
heathen:
I'm hearing a noise that sounds like static in a recent recording and I'd like to figure out what caused it. Here was my setup, using a Zoom F8 recorder:
Tracks 1&2: AT4031 mics, direct into recorder (no pre)
Tracks 3&4: CA14 omnis into CA9200 (+10 gain) into recorder
Tracks 5&6: dual recording of 1&2 at lower levels
Tracks 7&8: dual recording of 3&4 at lower levels
None of the tracks (main or the dual tracks) went higher than -6 all night (I don't think they even got close...particularly the dual tracks which peaked no higher than -16). I'm hearing the same noise on all tracks, though it seems quieter to me on the AT tracks. I've attached clips of the dual tracks (because those certainly weren't peaking high enough to clip). All I've done is amplify them using Audacity (and to be clear, the noise is heard even on the completely raw tracks).
I can't rule out the possibility that this noise came through the PA, but my paranoid side makes me think it's from my gear. I'm hoping that those of you with more experience will hear this and be able to recognize the sound, like "oh yeah this sounds like ______." Here's a download link for clips that contain the noise: https://we.tl/tc2qwjYvG2
morst:
Is it present the whole time? I don't even notice any noise at my low listening level, but my computer has a fan running.
I did notice that the relative polarity of the two samples appears to be opposite. Upward peaks on CA14 track look like downward peaks on the AT.
heathen:
--- Quote from: morst on May 14, 2018, 01:44:59 PM ---Is it present the whole time?
--- End quote ---
I haven't finished listening to the whole show yet but so far this is the only spot I've heard it.
--- Quote ---I did notice that the relative polarity of the two samples appears to be opposite. Upward peaks on CA14 track look like downward peaks on the AT.
--- End quote ---
Shit, I didn't notice that. What effect does that have?
ycoop:
--- Quote from: heathen on May 14, 2018, 02:11:39 PM ---
--- Quote from: morst on May 14, 2018, 01:44:59 PM ---Is it present the whole time?
--- End quote ---
I haven't finished listening to the whole show yet but so far this is the only spot I've heard it.
--- Quote ---I did notice that the relative polarity of the two samples appears to be opposite. Upward peaks on CA14 track look like downward peaks on the AT.
--- End quote ---
Shit, I didn't notice that. What effect does that have?
--- End quote ---
Someone please correct me if I’m wrong, but two sources having inverted polarity can result in sound cancellation when the two sources are mixed. Inverting polarity is a simple process in post, but as an additional process it can degrade audio quality.
Perry:
--- Quote from: ycoop on May 15, 2018, 08:44:05 PM ---
--- Quote from: heathen on May 14, 2018, 02:11:39 PM ---
--- Quote from: morst on May 14, 2018, 01:44:59 PM ---Is it present the whole time?
--- End quote ---
I haven't finished listening to the whole show yet but so far this is the only spot I've heard it.
--- Quote ---I did notice that the relative polarity of the two samples appears to be opposite. Upward peaks on CA14 track look like downward peaks on the AT.
--- End quote ---
Shit, I didn't notice that. What effect does that have?
--- End quote ---
Someone please correct me if I’m wrong, but two sources having inverted polarity can result in sound cancellation when the two sources are mixed. Inverting polarity is a simple process in post, but as an additional process it can degrade audio quality.
--- End quote ---
You are correct, it's all relative. By itself, an inverted source will sound fine, and there's nothing to gain by "inverting it back to normal" But if you're mixing sources, and one is inverted, there will definitely be some frequency cancellation. I have a pair of 4.7K mod AT853's that came to me inverted- the hot and cold are reversed. I just invert that track in post, before mixing with my AKG source. You'll notice the difference in the lower frequencies first- the bass will tighten up when the polarity of both sources match.
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