High Pitched Fluctuating Interference - Any ideas?

[SH04]

Hi everyone,
I've currently been working on dubbing over a film project, and whilst syncing a few of the recordings I noticed a high pitched fluctuating squealing noise over a lot of the lines. Unfortunately, this sound is very noticeable when watching the scene with other audio tracks, and kind of ruins it. Is there any way this sound can be identified and removed using audacity (or any suggested plugins, etc)? I've provided a link to an unlisted YouTube video where you can hear the noise (especially towards the end).
If anybody has any idea how to tackle this issue that would be brilliant - we're really trying to avoid having to go back and re-record.
Link: http://www.youtube.com/watch?v=YJfcd5Nh ... e=youtu.be (best listened to with headphones)
Thanks,
Sean

[steve]

Is the noise present in your original recording?
If so, could you post a short clip of a raw (unprocessed) recording in WAV or FLAC format and describe how it was recorded.
If not, at what stage does the noise appear?

[SH04]

Hi Steve,
Yeah it is, it appears directly in the project after being recorded with a USB studio mic. After discovering the noise we have tried recording with difference USB ports to make sure they weren't the issue, and have also checked the cable connecting the mic, as well as disabling laptop speakers/mic.
The audio was recorded with a USB studio mic direct to laptop, in audacity. It was a pretty simple set up.
I've attached a raw sample in WAV format, and would request once you're done with it you'd please delete it as it is owned content.
Thanks again for any help!
Sean

[steve]

Thanks for the sample.
I've trimmed it down to a 2 second extract which is sufficient to illustrate the problem and not pose a problem regarding copyright.
If you want the clip removing altogether I'll be happy to do so, but I think that it would be useful to keep it on-line for a little while as other forum helpers may be able to shed some light on the problem.

Here is the spectrogram view of the 2 second clip. The red wiggly line is the fluctuation interference.

firsttrack001.png (226.2 KiB) Viewed 1269 times

This is not an interference pattern that I recognise.

Are you able to make a recording in a different location with the same laptop, preferable in a completely different building?
Are you able to make a test recording on a different machine (preferably a Desktop rather than a laptop)?

[SH04]

Hey Steve,
Thanks again for such a swift reply! Even locating the interference has surpassed what I've been able to do, so that's awesome, thanks.
I've no problem with it being online longer, as you said maybe others will be able to contribute.
We have made recordings in different buildings with the same equipment to record concerts etc, and though the sound has been present in parts the music has often ruled it out as an issue and it isn't even half as bad, if appearing at all.
I just did a quick test on a desktop and there was none of the interference.
Sean

[steve]

We have made recordings in different buildings with the same equipment to record concerts etc, and though the sound has been present in parts ...

So you are saying that, with the same equipment in a different location, the interferences was still present (though less noticeable against the music)?
That would indicate that it is probably not environmental interference.

I just did a quick test on a desktop and there was none of the interference.

Which (happily) rules out the microphone as the cause.


So it sounds like the interference is being produced by the laptop.
Have you tried recording on the laptop with the laptop running on batteries (power cord disconnected completely)?

[SH04]

The microphone not being the issue is completely fine with me haha!
I just did two tests there without power running to the laptop, and there was none of the interference.
Would there be anyway to remove the sound from the existing files?

[steve]

Would there be anyway to remove the sound from the existing files?

Very difficult because it is a (widely) changing frequency.

I just did two tests there without power running to the laptop, and there was none of the interference.

It is not uncommon to get interference from laptop power supplies, but batteries do at least give you a workaround.


A different point - I notice that there seems to be a little bit of distortion in places. It may be worth trying, backing off from the microphone a little.

[SH04]

I feared that may be the case... Ah well! At least now we know and have some idea of the cause, or at least a way to avoid it a bit better.
And yeah haha, we've already redone those parts after noticing ourselves! The sample I sent was a pretty old one, but it had some of the more obvious interference.
Thanks for all your help anyway Steve, better start arranging some redos (luckily it's only select areas of the dubbing and not everything, I guess the interference had some mercy).