Hi all,

I shot a series of interviews the other day and when I got back to the edit suite noticed a high-pitched whine in the audio track. Didn't come through my headphones when I was shooting, weirdly.

I'm no good with audio editing or EQ - just wondering if anyone can tell me if it's possible to remove the noise, and how I'd go about it? I'm hoping because it's such a high frequency that I can just EQ it out.

I've got access to the basic tools in Media Composer, as well as Audacity.

Sample file can be heard here: https://drive.google.com/file/d/0B8J2rphA95EAWnRuWGhidmp4NkU/view?usp=sharing

Thanks very much.

Cheers,
Jody

How's this for a fix? Personally I noticed the background nose more than a high pitched hum. Trivially easy to do with the Izoptope RX6 software.

(Download audio from here: https://drive.google.com/open?id=0ByAMeJD3LP0RNkxpckkzdElTUDA)

Andrew

Thanks Andrew, sounds awesome - far better than the result I got using Audacity.

I just remembered I have Izotope RX4 - it came with an old Media Composer bundle. I might have a play with the de-noise feature and see if I can get a good result - would that be your recommendation?

Appreciate your offer to do the fix for me - I'll get back to you. I like to try and do these things myself so I know how to do it if it happens again in the future.

Cheers,
Jody

Have a go with the spectral de-noise filter and see how you go.

Andrew

Jody,

Not to be facetious at all. Were you using good cans? Good monitors and a keen ear should have heard that on set. I love my Sennheiser HD 280s. You had a lot of ambient backgroud noise there. That noise was easily missed. The closed back design of the 280s helps me hear what is getting recorded.

Also, where did it come from? Don't assume it was the location though it may have been. Check your own system before the next shoot. That does not sound like the usual 60htz ground hum.

Kind Regards,

Steve

Jody,

Not to be facetious at all. Were you using good cans? Good monitors and a keen ear should have heard that on set. I love my Sennheiser HD 280s. You had a lot of ambient backgroud noise there. That noise was easily missed. The closed back design of the 280s helps me hear what is getting recorded.

Also, where did it come from? Don't assume it was the location though it may have been. Check your own system before the next shoot. That does not sound like the usual 60htz ground hum.

Kind Regards,

Steve

Yep, good question. I use Sennheiser HD 480 headphones. I've used them for years, and have never come across an issue like this.

There was no ambient whine/hum that I could hear on the day of filming - it was a typical office building. The noise sounds like electrical interference to me. But I've used the exact same setup on several shoots since, and haven't had the same issue.

I came to the conclusion that it's an issue with my camera (Sony FS5). After a bit of testing this evening, I've been able to replicate it when the camera is plugged into mains power. The noise doesn't come through the headphones, but is heard on the recording. Unfortunately the camera is out of warranty.

Hey Jody,

Since you can replicate it with mains have you tried putting a ground lift adapter in line? It may be a .99 cent temporary fix. I always carry a couple of them in my kit for dirty power. Also the problem may not be in the camera, if your lucky it may be the transformer in the power supply. In my experience once a ground loop hum is getting through the device be careful, every source you plug into can be different, some worse than others.

Kind Regards,

Steve

Sorry if I am telling what you already know ;-)

Just ordered a ground lift adapter, thanks for that!

Jody, were you able to fix your audio with RX4?

Andrew

Ground lift?
noticed a high-pitched whine
Ground issues are linked to the mains frequency - so 60Hz/50Hz - as in low.

If you take the silence and bring the level up you can hear wideband digital noise. It's NOT a hum. It's data. The question is where it's coming from. The key is that you mention it happens when mains powered. It's identical to the noise many people have when plugging a computer (and especially Dell laptops in my experience) into audio systems. The noise almost certainly comes from the switch mode power supplies that provide the ideal conduit to get the noise into the device - recorder, camera, sound system, and it is well known - and one of the reasons most switch mode PSUs have a small ferrite ring on the cable. Trouble is it's rotten at it's job.

A simple-ish solution is to find an old, big loudspeaker you don't want - pull it to pieces and remove the circular magnet. Wrap maybe 10 turns of the DC cable going to the camera through it, and secure with tight electrical pvc tape. If you have a different brand PSU available, I'd give that a try.

Ground lifting won't help, because the PSU is almost certainly class II and doesn't have a ground to lift.

This is VERY common and something the manufacturers know about. It's often made worse when the device with the dodgy PSU is connected to ground through another attached device - so a mixer, or radio system of some kind that is grounded. Lifting the power ground often 'cures' the problem but DO NOT DO IT - it removes the safety feature and saves lives, only fools lift power grounds - sure, it solves one problem, but creates a better one.

Definitely some harmonics in there.

Andrew

Wow Paul, Spoken like a true A1. But not really, you explain things better than most A1s I work with. The best A1s I know are deaf in the left ear and can not explain anything logically. They know how their stuff works but they can not EXPLAIN it!

Yes it is a known safety violation to ground lift. It is also one I have no problem violating for a single device going into its own 120 power source. If it is show time and a projector is rolling with a 60 cycle band or one other component is going to have a bad record because of the hum they are going to get lifted and isolated. Fortunately we use Furman power conditioners and humbuckers most of the time so this is very rarely ever needed. I am NOT the guy that pulls the ground pin out of a stinger providing AC to multiple components and do not allow that to happen on my shows. We do not all work in our own theater every night. I have to depend on the power I get at any given venue, be it large or small, where ever it is. Ground lift adapters will stay in my kit for those rare occasions when I need one. Foolish or not by your standards.

Kind Regards,

Steve

Jody, were you able to fix your audio with RX4?

Andrew

Yes, it did a great job. Thanks for the recommendation. It even cleaned up the background noise quite well!

Paul - thanks for your explanation. I did notice that the noise was similar to that of an old computer PSU I used to own.

So, would buying a new Sony power supply potentially fix the issue?

Sampling thru RX6 Adv, and using their Spectrum Analyzer I found a whole host rascals running 4k 6k 8k 10k and 12k.

http://www.dvinfo.net/forum/attachment.php?attachmentid=37584&stc=1&d=1500206291

I punched in 4k and removed 4k 8k and 12k. This left behind those 6k and 10k. I punched in 6k and got rid too.

Spectrum Analyzer is your friend!

Auto mode on the de-hum is also handy. :-)

Andrew

Auto Mode? Where he?

He be lurking as "adaptive mode". :-)

Andrew

Ah yes, Adaptive was the "auto", is good, but I was wanting to nail/focus on just the High Pitched stuff. Adaptive comes back with many low end freqs. The Spectrum Analyser is a way to focus on the freqs needed.