Short vertical noise spike in the spectrum (G3 112 recorded sound)

legrevedotcom

legrevedotcom

Veteran
Heya

I'm having issues here with some audio that was recorded during an event. We had two micro port kits running into the Zoom H6 and only one channel is showing this issue.

It takes the form of a huge vertical spike in the spectrum viewer. My description would be that of a hard spike of white noise that comes and goes. Unfortunately this didn't show up initially and it wasn't till we were well into the event that the first spike came, so we couldn't jump in and fix it.
The spikes comes and goes in a variety from half a second to just over a second.

What is the proper name for this kind of noise and is it fixable? I tried tinkering around with the frequencies that aren't in the tone of voice area, but the spike seems to occupy all the frequencies from top to bottom.

I can gain it our where the guy on the podium isn't saying anything but I need to fix the ones overlapping his speech.

Cheers...
 
"What is the proper name for this kind of noise"
- Technically it's 'interference'. Some folks refer to this as an "RF hit".. A brief loss of signal which could be due to range, obstructions, multi-path cancellation or another RF signal stepping on the wanted one.

"is it fixable?"
- It depends.. on the severity and where the problem happened. If there's no dialog, it's usually quick and easy. If it's on top of dialog.. not so. A line or some of the same words from an alternate take or segment would be a possible option. OTOH, restoration software can sometimes repair this.
Can you post a clip?
 
Wow those are inexpensive wireless, at least the site I looked at. So yes you probably had one of two things happen. One is someone stepped on your frequency, and I didn't see any specs (the link sent me to a portable stage company?) But at that price point I wouldn't be surprised if it has a very short range so at any distance your chance of taking a hit probably goes way up.
The other thing it might be is low battery. Was someone trying to save pennies and using a used battery or worse a rechargeable?

A better wireless generally has some squelch function that would have just been a drop out instead of the noise blast. If Rick and I are correct then what happened is that your receiver lost your transmitters signal. What you are hearing is like tuning between radio stations.
that happens when something stronger than your signal is on or close to your frequency or it can happen if the transmitter signal is really weak. Batteries when they run down put out a lower and lower voltage. At some point on older and or inexpensive wireless sets you can get to where the transmitter is basically shutting down periodically. Better systems usually are designed so they just stop when this happens but I have seen older ones to this cycling thing where it comes and goes.

In either case a short burst might be fixable with something like iZotope's Rx spectral repair. But 1 sec is a LONG time to try and repair. And if there was talking then your not going to recover that.
 
I just thought of two things.

One When I said cheap I did a search for "micro port" and got a hit for a really cheap wireless system, but I see G3 in the subject so if you are using those you can file the "cheap wireless" info as maybe useful some time in the future.

The second thing is that if this recording was yesterday then you may have gotten hit by the RF bombardment we (the Earth) is going through for the next few days because of the really large solar flair. We are supposed to get some "storms" in the magnetosphere that will be very disruptive to wireless. It's actually so strong that it's going to be noticeable in electric power grids.
 
RF splats as we call them in the Uk can occur at any time with a wireless system but even in the confines of the BBC Scotland studios we have had a fair few unusual problems this week with high end sennheiser systems and IEM's.

A few other forums have also reported issues and some people are saying it is down to sunspot activity this week.
 
Unfortunately I don't think I can pass it off as sun spots as it was recorded the 9th. I see what you mean about the RF hits... I didn't realise this till into the event, but the conference arrangers were using their own micro port kit at the same time, so the two subjects had a total of four receivers amongst them :S I had mine going on separate frequencies of course, but I didn't get to check the other units.

I'm pretty sure it wasn't battery issues as I always buy fresh Philips or Duracell batteries and replace them for each speech, I never use rechargeables.

So far I've been able to remove a little over half of the hits, because of silence on the line, like you mention. I'll check out the use of words to do make-shift ADR.

But it's all good info you have given me. Atleast now I am a little better suited the next time we hook up a budget job :/

What is it with clients and bosses these days, it's always as much as possible for as little as possible. Terrible combination!
 
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Could it be cell phone interference? Cell phones "phone home" every few moments to let the system know what tower they're near and it has a characteristic rhythmic datdatdat...datdatdat...datdatdat spike pattern to it that is easily picked up by other audio gear nearby.
 
Steve House said:
Could it be cell phone interference? Cell phones "phone home" every few moments to let the system know what tower they're near and it has a characteristic rhythmic datdatdat...datdatdat...datdatdat spike pattern to it that is easily picked up by other audio gear nearby.
Click to expand...

I'm 98% sure it wasn't cell spikes. They didn't sound like and the frequencies available should be outside the cell phone band.

I can't post an example right now, because it's on the office computer, but it sounded like… well… imagine the sound of white noise. The imagine it climbing from 0db to 60db in 5-10 frames and then fast down again.

Could it be the lavalier cable dangling or rubbing against something? Like a silk shirt or something like that?
 
It's not a cable rub sound. Cel phone hits sound like an old dial up modem, sort of (for those old geezers that remember that, for young punks there is a homework assignment). And they inject on wired systems also, it has nothing to do with stepping on your transmission it is this huge RF burst that just jumps in to the audio.

I used to put my iPhone close to the mixer in class the first day so that it would pop out of the speakers at some random moment. Then show that it was not even touching any geara nd that was why you need to TURN them OFF when shooting.

If it was regular it could be a beat frequency of the other wireless transmitters? Or it could be RF junk in the building. There is a beach I recorded on in the Bay Area where one of my mics was "hearing" the radar sweeps from a navy ship. It was weird but if you looked close you could see the dish rotate in sync to the noise. That particular mic was/is fairly sensitive to RF. I could also trace out the underground antenna array in another location using the mic like a Geiger counter.
 
Noiz2 said:
It's not a cable rub sound. Cel phone hits sound like an old dial up modem, sort of (for those old geezers that remember that, for young punks there is a homework assignment). And they inject on wired systems also, it has nothing to do with stepping on your transmission it is this huge RF burst that just jumps in to the audio.

I used to put my iPhone close to the mixer in class the first day so that it would pop out of the speakers at some random moment. Then show that it was not even touching any geara nd that was why you need to TURN them OFF when shooting.

If it was regular it could be a beat frequency of the other wireless transmitters? Or it could be RF junk in the building. There is a beach I recorded on in the Bay Area where one of my mics was "hearing" the radar sweeps from a navy ship. It was weird but if you looked close you could see the dish rotate in sync to the noise. That particular mic was/is fairly sensitive to RF. I could also trace out the underground antenna array in another location using the mic like a Geiger counter.
Click to expand...

So better gear might not have saved me? Just trying to figure out if I should use this issue to persuade my boss to start throwing more money into these productions.... Right now, I'm sitting here, trying to pick out words here and there to patch up as much as I can x) Ain't exactly pretty.

I'm inclined to think also that the premise wasn't too great... concrete walled room with 200 people half of them using their iPhones / pads every now and then during the conference. And the sound recorder was placed at the tripod camera in the middle of the room.

Lesson learned :/
 
Have we established what the kit was audio ltd microport was a pretty decent system, but even if it was a rock bottom cheapo system, there is no guarantee that an expensive one would have been immune. Keep in mind that if you view the radio mic spectrum with an analyser, it is NOT a big empty space, there are numerous but low level spurious signals there, many are harmonics from lower bands, some are unfiltered products from other devices, but usually low enough to be no trouble. Radio mics use a wide bandwidth and can be quite tolerant of narrow band RF in the band. The problems happen when multiple spurious signals combine, perhaps as daft things happen, like maybe a bus or metal sided lorry goes past that reflects a more distant RF source, which might then beat with another producing a sproggie on your operating frequency, as the lorry vanishes the mixing stops and the interference goes. Continuous interference tends to be something operating on your frequency, but phuts and noise bursts are usually random mixing of two or more sources. It's not impossible for people to also operate on frequencies outside the official band 38 limits, and either side of these can be the first harmonic of the UHF AM military airband, so an AM transmission at fairly high power from them can produce a RF burst quite near your operating frequency. I did some work at an RAF base a few years ago, and expected but didn't get, interference from the mega radar nearby, however their comms systems leaked into everything. Don't forget the maths thing with RF. Frequencies can beat together, get added together and subtracted from each other, generating fairly decent levels at unexpected frequencies. Interference happens. Digital systems are more immune, but an RF burst is still RF and the receiver attempts to make sense of it. Some strong ones can cause a silence on a pilot tone engaged system, because the burst is on the right frequency but isn't valid, so you get silence. With pilot tone off, you get the nasty hiss-phut. If it repeats and repeats, then you need to move to another frequency. RF just does this kind of thing, hence why cables are better. As soon as you use invisible cables you are on notice. Just how it is.
 
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