Audio pros: can you explain this?
 

Ok I'm going to try and describe this "problem" to the best of my ability. I was testing my UWP-C1 wireless with my new ECM-77 lav mic this afternoon. I was only about the distance my headphones would reach from my camera (as I didn't have an assistant to help test it for me). Anyway I noticed when I turn the attenuation up on the transmitter and try and make the audio louder by tweaking the input levels on my PD-170 I started hearing a weird phenomenon. Everytime I would stop talking abruptly I'd hear an aftershock (in sorts) of hiss. Kinda like the hiss you hear when you have the levels up really high- well it sounded like the hiss would raise and lower as I talked. If I hummed for 3 seconds then stopped for a brief second after I stop I'd hear a louder than normal hiss that quickly lowers. Kinda like the hiss raises anytime the camera recieved an audio signal. After close monitoring I could definitly hear the hiss during my vocals. It seemed like it got louder only when I talked or made a sound.

Is this normal? What causes it? How can I avoid it?


Thanks in advance.

Sounds like you are describing the wonderful world of Automatic Gain Control....AGC. If you can disable it on your camera, kill it. It's not your friend even though the camera manufacturer wants you to love it.
Thye PD 170 is already a little noisy, and the AGC doesn't help. I'm almost sure you can kill it.

That's a good assumption- it definitly sounds like a problem caused by AGC. However I'm positive it was off because you have to disable it to get manual control on your audio input(s) which I had.

Hmm, I wonder if the Sony wireless has AGC of some kind of noise compander or compression feature? Does this phenomenon happen with the OEM mic?

Turn the NR off on the 170. That will solve the problem.

Mike might be on to something because NR is ON by default. What exactly is it? Noise Reduction right? Why does it cause this? I did explain it correctly right?

I think there is another microphone inside that is used to oppose the camera sounds picked up by the microphone when mounted on the camera. But if it doesn't pick up the sound, then what you hear is the tail-end of the cancellation signal not being opposed. BT,BBBT (Been There, Been Bitten By That)

But that effect went away when I turned it off on my camera. Sony tells you to turn it off in the manual. Drove me nuts because I did an important, and expensive Voice-Over with it on when the camera was new.

"BT,BBBT (Been There, Been Bitten By That)"

LOL! That's a new one I'm going to add to my repertiore.

That's interesting Mike. I wonder why they would have it ON by default and tell you to turn it off in the manual. I wonder if it's the same in the PD-170 manual....I'll have to look for it (remember what section it was in)?

So the hissing "aftershock" following and during vocals is what you heard as well? Just making sure I described it correctly.


Thanks.

It's on by default because it does marvels when you are using the on-camera microphones, whether it be a shotgun like the one supplied or the stereo in-camera kind (I have a PDX10 so I get to have them both).

Stupidly, you can't turn it of for one channel and not the other one so if you are using a lav and want to have the on-camera as a backup or for ambience you have to live without NR.

<<<-- Originally posted by Glen Elliott : That's interesting Mike. I wonder why they would have it ON by default and tell you to turn it off in the manual. I wonder if it's the same in the PD-170 manual....I'll have to look for it (remember what section it was in)?

So the hissing "aftershock" following and during vocals is what you heard as well? Just making sure I described it correctly.


That's it


Thanks. -->>>

Re: Audio pros: can you explain this?
 

<<<-- Originally posted by Glen Elliott : I was testing my UWP-C1 wireless with my new ECM-77 lav mic -->>>

Is this issue true only when used with the ECM-77 ?

Be sure to follow up on this post Glen.

Personally I don't think it's NR or AGC.

I think it's phase, noise-tails, breathing, fizz... whatever you want to call it. I call it "sizzle".

Some mics bring it out more then others. So far I've had the best luck with trams and an mke2.

In a synthesized UHF wireless set you have a couple things working against you. That frequency selectivity causes some SNR problems that make it necessary to design companding into the circuit. All the technology of convenience creates a compromise between doing one frequency perfectly or a multitude of them with a little sizzle. Sometimes you won't get any sizzle. In my experience the sizzle is hard to predict, but the more sensitive the mic (and larger the diaphragm) the worse the sizzle... but not always. It's a weird thing.

Try to use brand new batteries and check all switches and connections every time. Sometimes a switch may not be quite on and that can add extra noise.

But as far as sizzle I hope the others here are right and I'm wrong, but I doubt it.

UPDATE

Did some more tests tonight and tried turning off the NR- no dice. Still there. It's definitly more noticable on the ECM-77 probably due to the fact it's so sensitive to begin with. I switched to the onboard mic and it was GONE. Sounded fine...so it's definitly something related to the wireless system. I mean it's not too bad- granted, it's more audible on headphones turned all the way up. On the TV is there but can only hear it when I play the audio out through my Bose system.

The aspects that seem to affect it are the mic input level on the camera itself. I get less "sizzle" (or whatever you call it) when I keep the attenuation OFF on the transmitter and bump the input levels on the camera down. Conversly I hear more "sizzle" when I do the opposite. When I turn the attenuation up on the transmitter and crank the mic input on the camera it's MUCH more noticeable.

Do you think it's because of a channel I chose? I don't think it's interference though. Is it something that's inherent of a lower end wireless system?

Glen, noise-tails (as there properly called) are not that uncommon in many wireless systems. As you're discovering you can change settings between the wireless and the cam to help it along.

I would do the most you can with settings and then decide whether or not the sizzle is better or worse with another mic. If that particular mic brings out more sizzle then you have another choice about whether to keep that mic or get a different one.

The intention of my post was to put your mind at ease about having some sizzle. I've got two Lectro systems and ocassionaly I'll hear some sizzle. If I hear any I do one of the following:

1) make sure I've got NEW batteries in.
2) make sure the switch is ALL the way on 'cause it comes on before the switch is fully seated in it's detent.
3) check all connections.
4) adjust levels on cam vs. levels on wireless to minimize it.
5) try a different mic if necessary and available.
6) use an xlr if the lav I'm using fits the ta5f/xlr powersupply.

Depending on how critical the vocal is you may not even notice the sizzle in your final product. Of course I don't know exactly what you're hearing, but I'll bet you dollars to donuts that I can email you a clip saying, "Is this the SIZZLEphfffft", and you'll laugh 'cause you'll know that I know what you mean. If I plug an Oktava on my wireless it sounds great, but then if there's a stong sound like pinging a glass with a pen, you hear, "PINGsssff"... or if I get RIGHT on the mic I can force it with words.

I would try all of the above and try not to lose too much sleep over it. You'd have to spend THOUSANDS or else use a big-ass rack-mount unit like they have at concerts to guarantee no sizzle ever.

This has been my experience with mics I've owned... as you see it doesn't seem to follow any logic:

1) tram... minimal sizzle.
2) mke2... minimal sizzle.
3) m58 newsmic... minimal sizzle.
4) sm86... sizzle-mania.
5) nt3... medium sizzle.
6) me66... minimal sizzle.
7) 4073a... medium sizzle.
8) mk012... sizzles my nizzle.
9) nt1000... minimal sizzle.

So there you have it. No real rhyme or reason as far as I can tell. Minimal means little to none... I used to think my Lectros were as perfect as wires, but as soon as I hook up a large diaphragm mic it's obvious that wireless sets remove a good chunk of soul. So unless you're going to get a Zaxcom I'd prepare for the ocassional annoyance.

Hmm. Matt's statement make sense. I seem to have experienced what he describes but it's very subtle, at least in my setup.

The problem might also lie with the PD150/170's audio circuitry, the PD150 is famous for it's not-so-great audio. I don't have the PD150 at hand so I can't test it right now, but perhaps you are suffering from this, or from a combination of what Matt describes and some clipping in the preamp.

I usually att both the the camera's input and the wireless system (-3dB), otherwise the output of the Sony wireless is too hot for my taste and clips the preamp, even if you bring the input level down.

You could try bypassing the camera's preamp alltogether by setting the channel to line level and making a cable to connect the receiver using it's headphone output. Of course that will be unbalanced, but the cable is so short and you are using batteries so it really should not matter.

Hope this helps.

You can't bypass the pre's. it only an attenuation. It does help but the preamps stay in the circuit.

> You can't bypass the pre's. it only an attenuation. It does
> help but the preamps stay in the circuit.

Really? How unfortunate. I thought the famous 'BBC mod' was only for the VX cams because the PD and PDX cams had real line level... it's so stupid, just a simple rewiring, how could Sony be so lazy?

It's more involved than you might imagine. http://www.gregjwinter.com/modification2.htm

Matt thanks for your input- it has eased my mind greatly (well sort of). At least I know I don't have faulty gear, and it's something other people have experienced. Heck, I'm glad you understood what I was trying to explain- was worried people would shug and wonder what the he** I was talking about.

Anyway between my two lavs the ECM-44, and 77- like I said it seems the 77 produces a hair more noise tail (thanks for the clarification) than the 44. Despite this fact I'd still chose this lav over the 44 simply because of it's frequency response- it produces a much richer natural sound. The 44 sounds a bit tinny for my taste.

So doing on going extensive test in regards to channels and frequencies will be uneccessary? It sounds to me, the way you described it, that it IS something inherent of wireless systems though different mics react differently in any given situation. Oddly enough though you listed the ME66- were you using it in a wireless setup somehow? Thought it was for on camera shotgun or boom. Anyway it's pretty easy for me not to imagine using an XLR boom in a wireless beings my only experience with a wireless system has been this one (UWP-C1) which uses locking 1/8" ports rather than xlr.

I have heard that for wireless systems to work they have to compress the signal way down for transmittion and one recieved it's uncompressed and fed to the camera. Does that specific point lend to the fact it's inheren't to wireless systems.

Lastly the size of the diaphram didn't seem to make a difference (well in my finite tests at least). The 44 looks like the size of a marble, and the 77 a bit larger than a matchstick...yet the 77 exhibits a bit more noise tail- though, again, that could only be my perception because the mic is so hot compared to the 44.

Glen, that's why I said it doesn't seem to follow any logic. I'm sure there's a scientific reason why some mics bring out (or cause) more noise-tail then others, but I don't know what that explanation is.

The me66 has a "crispier" sound then the other mics I've used and I think that's why it masked the noise-tail more then the 4073a.

The one thing about this hobby that sucks is you NEVER have enough... there's almost always another level above what you can afford... Lectros are highly regarded, but they 'aint Zaxcom.

To address another point you made; a wireless boom is a real blast when you must use one. Imagine man on the street stuff and you've got a wireless boom guy. You can frame your shots from a distance, zoom in a bit, and the boom is still feeding you great sound. Even if you're right next to your sound guy it's nice to not have to think about each other's "cord managment" or worry about pedestrians and other surprises catching a cord. If you watch the news or "The Daily Show" (one of my favorites) you'll see the little plug-on "box", or butt-plug, as Hollywood decided to call it... That configuration of transmitter is cool 'cause you can plug it onto almost ANY xlr mic and turn it into a wireless mic. The plug-on supplies phantom power and transmits the signal too. The bummer is that sometimes you lose so much of a mic's soul that it's main useful purpose is strictly dialog... and at that it's for the words that convey information rather then feeling.

For the real sound guys with digital recorders it's not an issue 'cause the boom feeds the recorder that's on their belt... So they can get wired sound apart from the camera, but I don't have any of that gear... yet.

Wow, interesting stuff. Yeah speaking of the ME66 I have one and in dire need of the red "dot" mod, where they remove a capacitor in the K6 so the mic isn't so darn sensitive.

Here's another question for you- in all honesty I still think the quality of sound from the ME66 dwarfs even my ECM-77, should this be true....or is it completly expected beings it's a wireless system and not top of the line to boot. In other words what kind of expectations should I have from my wireless system compared to my camera mounted, phantom powered ME66?

That's a loaded question Glen. The me66 is a totally different kind of mic then the Sony lav. In my own experience I found the tram or mke2 to be about equally detailed to the me66... They had a very similar sound and that's why people like trams for mixing with shotguns. Most people won't notice one mic over the other. But combining a wireless AND a lav mic to draw a comparison to a wired shotgun isn't really fair. Speaking from my own experience I've gone through a phase with every new mic purchase. I buy it with a set of expections... many of those are met, but a few are left short... then I look for flaws in the system. Eventually I realize that's why people have so many different mics. It's because they all do different jobs. As you first go off the deep end of the GSA (gear sluts anonymous) you tell yourself that you're being irrational, but the fact is that the lav and the shotgun serve two different purposes and it's not a fair comparison to put them in the same boat.

I often use a shotgun and a lav at the same time, on different channels. Imagine a guy interacting in a group... there will be times when you want the sound of the "whole" and there will be times when you want only your speaker. If you use both mics you can choose.

I had a guy interviewing random people in a festival here in St. Louis. There were street performers and typical wack-jobs and sometimes my guy would make funny comments back to the camera. At this time I couldn't even hear him. He was too far away and I didn't want to spook the interviewEE... so I hung back. Ok so the girl being interviewed is being heckled by her friends and it's really funny. The shotgun hears them fine but I can't really hear my guy OVER them and I can't really hear the girl's voice seperate from her friends. Now which mic is better?

Take your pick. Do you want heckling comedy? Or do you want to hear your subject and the interviewee? If you're going to choose then you better go with the wireless! But there will be times when you want one or the other, or a mix of both.

Imagine the shotgun like a flashlight with a broad beam. If you want the sound in that beam then you want a shotgun. You'll hear things ahead of the subject and behind it AND quite a bit to the sides.

The wireless is like having a remote control bubble of sound capture. It MOSTLY gets sound within a 5 to 7 foot bubble around the omni. That can be damn handy!

At this point I pretty much use the wireless when I have to, but my normal instinct is to grab the best mic in the bag THAT WILL WORK... sometimes the best mic in the bag isn't the one that will do the best job. Make sense?

I had the sizzle thing happen when I tried to use one lavilier wireless mike for two people.

This techique worked really well in the past when I used my samson $300.00 wireless, but when I rented a much higher priced Sony with 99 channels, the sizzle was there.

I was only doing audio acquisition so I shot it with both HI-FI and Dolby linear on S-VHS. The HI-FI did not like the sizzle sound and exacerbated it, the Dolby linear channels were much better.

I'd say it's the microphone. I forget which mike they put on the $300 Samson wireless but if you can get one of those mikes it would be interesting to see if the problem is reduced.

Yeah that makes sense. For upcoming weddings I'm planning on using my ME66 at the same time as my UWP-C1/ECM77 wireless/lapel combo. Set one for each channel (beings they are mono) and pan in post as needed.

Unfortunatly I don't have the cashflow to continue to buy lapel mics to test for noise tails. I already hashed out an additional $230 for the ECM-77 to upgrade the 44 that came with it- which, despite the slightly heightened noise tails, was well worth it for it's more rich natural sound.

Thank you greatly for all of your input. Maybe in the future I can get my hands on various lapel mics to test to see if they continue to have the noise trail problem. Hopefully they will be non-sony mics to see if it's a company specific lav issue.

Wow, there's a bunch of issues in this thread.

1. The "sizzle" question. all wireless mics (except one) use a noise reduction technique called Companding. It acts like an automatic gain control in reverse. When it hears no sound over a minimum level, it attenutates (lowers) the audio level. This masks the noise inherent in the RF circuitry. This noise is always there, but your brain doesn't hear it under dialog or other audio. What you are hearing is the interval before the noise gate kicks in.

2. The differences between lav mics. Different mics have different frequency responses and different output levels. These differences interact with the companders in varying ways. A very hot mic will keep the noise gate open longer, so you hear more RF noise. A mic with a rising high frequency response (like the 77 or the Tram) will also fool the compander.

3. Difference between wired & wireless. Well, no compander, no RF noise.in the wired version.

4. Difference between lav & shotgun. Most lavs are omnidirectional. Shotguns are very directional and reject sound 90 to 180 degrees off axis. They also tend to have larger diaphragms which give netter noise specs, and are more expensive. Which would you expect to sound better - a $200.00 lav or a $500.00 mic?

Hope this helps!

I hate noise gates.

I suppose if they had a true digital delay gate and the gate didn't "miss" the first millisecond of sound after silence I wouldn't mind it, (but they don't) but then you would have to delay the video an equal amount.

Since it appears that some digital cameras are adding their own mystery to the issue, do you guys ever hook your headphones up directly to the wireless receiver and compare that with how it sounds when the headphone is directly hooked up to the camera?

Sure, you want to check the woreless' output beore you start shooting. But once tyhe audio is in the camera, there's not much you can do about it.

I should add a few things about companding to complete the picture because there's more than just noise gating in the transmitter. There is also compression. The transmitter compresses the dynamic range so it takes up less RF bandwidth (actually called "deviation" from the carrier frequency) and improve the signal to noise ratio. Then the receiver expands the audio back to something resembling the original.

I posted recently about hearing this sizzle with a
Samson Airline system -- and this was when it was
not plugged into a cam -- just had phones
hooked up to receiver. Haven't had the chance to
investigate it furthur, and don't know if it has to
do with the phones monitoring. Haven't noticed it
with cam use, but maybe it's a developing problem.
It's like a whishhhhhhing noise at the begin and
end of words. Is that what you are experiencing,
Glen?

It's like a whishhhhhhing noise at the begin and
end of words. Is that what you are experiencing,
Glen?

Pretty much....Yeah. If you listen really closely you can even hearing DURING words as well.

Maybe you should try plugging phones direct into
the receiver, bypassing the cam. Have someone
talk into the Tx and listen for it then.

Right. What you are hearing is the system's noise floor when the noise gate is open. That's the difference between the cheap gear and the expensive gear.


However, try a different frequency, or one in a different frequency band. You may find one that has a lower RF "ambient" noise.

Glen,

Comparing the ECM 77 and a ME 66 is like apples and oranges, especially if one is cramped by a wireless connection. I did a quick test with mine where they were both hardwired, one to each channel. Lav in it's normal place cliped to shirt, 66 on a stand about 4 ft in front. The 77 won hands down for in my opinion. You may want to try a similar test to set your mind at ease about the mics. I'm guessing the wireless connection on your 77 is really limiting the quality.

In terms of circumstance when it comes to the test you describe, how the audio will be edited should be considered.

For instance, if you need to mike two people, the interviewer and the interviewee, the one ME-66 in between them may deliver excellent audio quality that won't require additional sound editing which will be required if you use two lavalier mikes.

If you use two lavalier mikes, you may find that you have to "duck" the mike not being used, so if you have a lively exchange going on, two lavs can be a pain to work with.

If you don't plan on using the voice of the person asking the interview questions, then one lavalier mike is probably better than one ME-66, but be aware that certain unpleasant sounds get amplified as well.

Yeah I'm planning to use my wireless/shotgun combo for wedding videography. The main reason for wireless is to capture vows. Granted a little noise tail won't "hurt" me too much expecially beings I'll probably have a music bed in the background though I want to see if I can lower it's audibility (is that a work?) to the best of my ability before I go into post and throw a soft music track under it, etc.

A friend, another forum member, just picked up the Senny Evo100 wireless system from B&H yesterday so we are going to try and compare them tonight. We are also going to compare his Audio Technica (forget the model #) to my ME66.

The Samson wireless mikes tend to do a good job of picking up a small circle of people, such as during wedding vows.

However I don't know if you can get diversity style with the Samson wireless.

Another consideration is if you only use a mike on the camera you will get a shift in audio quality and tone as you move around the group. (assuming you do some moving, not too much because they would probably be frowned upon, but sometimes you have to move or you will miss a moment).

Ideally you probably want a wireless mike attached to either the person administering the wedding or on the groom, PLUS a mike on the camera as back-up.

Sometimes placing the mike on the loudest talking person will not be the ideal way to go, you might find it wiser to put the mike on the softer speaking person, (usually the groom), this should allow for the pick-up of both the bride, the groom, and the priest/rabbi/preacher...