Cell Phone Interference in Recording

[Hattonkeys]

First post here, I am using DP9 and I have a solo piano recording where I have RF interference (probably from the cell phone of an audience member) on the track of my tube mic. Does anyone know the best plug-in to use and how to isolate and get rid of this unwanted noise? I tried to use the MOTU Dynamic Equalizer, but I'm having trouble figuring it out. I am a noobie to recording, so explain in simple terms and thanks so much in advance!

Hattonkeys

[Shooshie]

If you have interference in your mic signal, it's probably too late to fix it, but you may be able to minimize it by using noise reduction software. There are several kinds. Waves makes Z-Noise, which can adapt to changing noise signals, but it works best if you can find a blank spot (no music happening) in which it can make a profile of the noise.

Isotope makes a plugin called Rx, which has several noise reduction methods in it. You may have more luck with it. I really don't know which would be best for this situation. Be forewarned that noise reduction software does not come cheap. I think it's probably the most expensive of all plugin types.

As for ways to eliminate noise in the future, be sure you are using shielded mic cables. Regular ¼ in jacks on balanced cables may be shielded from interference if they terminate properly in TRS plugs (tip, ring, sleeve). You can look up TRS to learn how to terminate them for elimination of interference. But the best bet is to use balanced cables with XLR plugs. They are designed for long microphone runs without picking up radio interference. It DOES make a difference. I was using a quarter-inch unbalanced cable for a long run to a talk-back amp and speaker between the control room and studio, and it picked up an AM radio as if it were an antenna. Replacing it with an XLR fixed it 100%.

Shooshie

[stubbsonic]

It really depends on the type of noise you are hearing. If it is a very regular kind of tone, hiss, or digital glurbiness, then regular Noise Reduction software might work best. If it is very irregular, it might be more challenging to do in an automated way.

If it is various blips and cell phone noise (like dit ditit dit ditit dit ditit , etc). I'd suggest looking at some kind of spectral editing. I think izotope might have one as part of their product line. This shows the frequency as a vertical (Y) axis, and time as a horizontal (X) axis. You can even use tools to select things you SEE in the spectral plot. Some tools will even let you select one area and then it will automatically select above areas that are overtones.

Depending on the nature of the noise, and how much it might overlap with the frequency content of the piano track, you might be able to reduce the noise considerably. But I don't want to get your hopes up. It's always a crap-shoot with NR, especially that kind of noise.

Good luck.

[mikehalloran]

Noise reduction software works best when it can listen to a few seconds of the problem.

Izotope RX 5 should be able to remove quite a bit. It's on sale through 10/28 for $299 or $253.99 through some retailers including AudioDeluxe.

RX 5 Advanced will be a little better, probably not enough to justify the extra cost unless you need the additional features such as I do. $999 – $848.99

RX works better as a stand-alone app on difficult material but the plugins are often good enough – quite good, actually – but sometimes... Some of the tools only work in stand-alone mode.

You can download both for evaluation. Unfortunately you can't save but at least you'll know if it's going to work for you.
www.izotope.com

SoundSoap 4 is $79.99 from the App Store. Can't evaluate, however.

Sweetwater has told me that they can match the sale prices. Since they help support this site, they get my business when I can throw some their way.

The cause of the noise is the greater concern. Is it the mic? preamp? defective cable? tube? Until you can suss the source, you might want to bench that piece of gear.

A little hiss and hum out of a nice tube amp is often part of the package. RX in post will clean that up nicely. I have saved many live recordings with that tool, some of them quite old (I need the Advanced version).

[kassonica]

Izotope RX 5

forget soundsoap

waves can sometimes work if its not too bad...

[Hattonkeys]

Thank you all for your responses!

I also would like to figure out what went wrong in my recording chain so this can't happen again. The interference definitely seems like the RF variety, such as when you put your cell phone down by an amp and it is about to receive an incoming text-same sound exactly. There were about 20 people in the audience all with cell phones on silent mode. When I looked at the wavelengths in the De-Esser plug-in, I could clearly see the interference happening during the silence of the piano in the 2-3K bandwidth.

My SE Electronics condenser tube mic has a proprietary 7 pin cable that goes to the pre-amp box with the tube in it, and from that box I have an XLR cable that goes into my Presonus Audiobox 22VSL. So this technically shouldn't be able to happen with my balanced connection? Maybe the cheapest fix would be to replace the XLR cable and see if it happens again?

For this recording, I can just use the mono signal from my other pencil mic for the offending sections, since the recording is not of super-high importance and I can't afford an expensive noise reduction plug-in.

[mikehalloran]

So this technically shouldn't be able to happen with my balanced connection?

The mic body, preamp and any power cable are potential sources of such a noise. Are you going into a mixer? Do you have another box connected?

Are you using an unshielded power strip? That one happened to me just last month. Fortunately, I noticed the problem right away so I knew the culprit and was able to fix it. My iMac's power cord turned into an RF antenna and was sensitive to my iPhone If I got it too close.

[Hattonkeys]

I had my audiobox going straight into my laptop via Usb. I decided to buy the Furman SS-6B power strip in the hopes of eliminating possible RFI/ EMI interference as I was just using an el cheapo power strip. Thanks for the tip, Mike

[daniel.sneed]

This will be of no help for your actual tracks, but:
As a major rule, while tracking audio (or video) in presence of people with cell phones, they should be asked to turn them completely off. Not just silent mode.
Same apply with any picky live performance including audio.

Spectral repair (in iZotope RX) may help much in getting rid of that cell phone noise (or mostly attenuated).