Automatic mic mute (stage)

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joaquins

joaquins

Well-known member
Joined
Feb 25, 2012
Messages
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Location
Argentina
  It's a detector that cuts the mic "off" (40dB or so) when no artist is in front of it, picture a guitar player and singer, loud amp behind him, when solo starts he goes to the side, the voice mic picks a hell of a lot of the amp. Not with this device, if the guy is in front of the mic singing the mic is open, if he goes away it's closed.
  The sensitivity (distance) should be adjusted, phantom powered, little impact on the signal integrity, but as usual, on the stage isn't as critical as in the room.

What is known about something like this? Any project already chewed around?

Here is a comercial example.
http://www.optogate.com/pb07_uk.html

My first approach would be a switch just shunting the mic signal with a low impedance analog switch, if atten isn't enough an extra switch in series should do. This controlled by a tiny µC reading a IR distance sensor, the example mentions a 3 bit code to avoid noises, I guess some "lock-in" should be done to avoid stage lights interference. The trimpot going to an analog input controlling the sensitivity.

I don't know a more generic name either to google it around some more. Any info appreciated.

JS
 
joaquins said:
  It's a detector that cuts the mic "off" (40dB or so) when no artist is in front of it, picture a guitar player and singer, loud amp behind him, when solo starts he goes to the side, the voice mic picks a hell of a lot of the amp. Not with this device, if the guy is in front of the mic singing the mic is open, if he goes away it's closed.
  The sensitivity (distance) should be adjusted, phantom powered, little impact on the signal integrity, but as usual, on the stage isn't as critical as in the room.

What is known about something like this? Any project already chewed around?

Here is a comercial example.
http://www.optogate.com/pb07_uk.html

My first approach would be a switch just shunting the mic signal with a low impedance analog switch, if atten isn't enough an extra switch in series should do. This controlled by a tiny µC reading a IR distance sensor, the example mentions a 3 bit code to avoid noises, I guess some "lock-in" should be done to avoid stage lights interference. The trimpot going to an analog input controlling the sensitivity.

I don't know a more generic name either to google it around some more. Any info appreciated.

JS
Click to expand...
This subject has been debated on the French site "Les ingénieux du son". Looks like the Optogate is the only one currently available. There used to be a Micmute, but apparently it worked so bad it was discontinued.

Muting is the easy part; shorting the mic is easy (and silent). Some analog switches have a very low Ron; MAX4680, with 1.25 typ. Ron, would provide about 40 dB attenuation.
Presence detection is the tricky part. Most avilable sensors are movement detectors, they wouldn't detect a person standing with no movement (some singers are exactly like that, not everyone is Mick Jagger).
If you look at so-called "presence detectors" for alarm systems, they are in fact very sensitive movement detectors; I think that wouldn't work very well in a concert situation, because their range of detection is too large.
This leaves the choice open to infrared (http://www.sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2y0a21yk_e.pdf) or ultrasonic solutions (http://maxbotix.com/documents/LV-MaxSonar-EZ_Datasheet.pdf).
The 30mA current draw of the Sharp solution seems to be a no-go.
I'm not sure there's need for a uC in such a system; proper timing and hysteresis should suffice.
 
It's called a noise-gate and are there are multiple design approaches.

JFET hard shunts can be inexpensive and effective, VCA based downward expanders are more gentle acting and less objectionable than background cutting out and coming back. Both are mature technologies.

There are also small gadgets designed to operate from phantom power and located at the mic level output.  I have seen several of these come and go over the years mostly from small companies that come and go. Not really a big ticket, mass market product.

JR

PS: Perhaps search noise gates, and/or downward expanders.
 
abbey road d enfer said:
This subject has been debated on the French site "Les ingénieux du son". Looks like the Optogate is the only one currently available. There used to be a Micmute, but apparently it worked so bad it was discontinued.

Muting is the easy part; shorting the mic is easy (and silent). Some analog switches have a very low Ron; MAX4680, with 1.25 typ. Ron, would provide about 40 dB attenuation.
Presence detection is the tricky part. Most avilable sensors are movement detectors, they wouldn't detect a person standing with no movement (some singers are exactly like that, not everyone is Mick Jagger).
If you look at so-called "presence detectors" for alarm systems, they are in fact very sensitive movement detectors; I think that wouldn't work very well in a concert situation, because their range of detection is too large.
This leaves the choice open to infrared (http://www.sharp-world.com/products/device/lineup/data/pdf/datasheet/gp2y0a21yk_e.pdf) or ultrasonic solutions (http://maxbotix.com/documents/LV-MaxSonar-EZ_Datasheet.pdf).
The 30mA current draw of the Sharp solution seems to be a no-go.
I'm not sure there's need for a uC in such a system; proper timing and hysteresis should suffice.
Click to expand...

  Nice info, my french is quite rusty, I wouldn't be able to buy a cup of coffee I guess...  ::)

  The µC would allow to tweak the prototype much easier than other approaches, I don't think it's needed either.

  I agree the distance measurement is the issue, either optic or acoustic distance measurement would depend on the cloth, color and texture. Easy to detect white leather, not so much black fur... So, there is an unknown variable, unless detecting the face directly leaving something funny in top of the mic, as long as it's small enough shouldn't be a problem. The sensor not only needs to be feed from phantom but be able to share the phantom with a mic, just in case the singer doesn't like the SM58.

  Maybe a silly idea and too hard to execute, but an electret mic, inches apart from the mic in question (as the other sensors), correlation meter, if too much correlation there is no useful signal, if there's little correlation, that's our singer. Complexity is of course much greater, but we are talking of a different kind of functionality.

JS
 
JohnRoberts said:
IIRC one cheap and dirty approach was a floor pad/switch where the mic is muted when nobody is standing in front of the mic.

JR
Click to expand...

I've thought that while back when I first approach this, the idea was discarded with a teacher at the moment but I don't remember why  :eek:

JS
 
http://www.banggood.com/DC-5V-100mA-Photoelectric-Sensor-Optoelectronic-Switch-p-1124909.html
What about this one?
Like the correlation idea BTW...
Jakob E.
 
The correlation idea reminds me of Lemmy Kilmister microphone. Basically 2 sm57 side by side supposed to be out of phase. Lemmy had to sing very close to one mic for it to work. This allowed them to get very loud sound on stage.
 
JohnRoberts said:
...
PS: Perhaps search noise gates, and/or downward expanders.
Click to expand...

  A JCM800 or a young drum player can easily trigger a gate set to open with the singer, this leaking problems are worse on small spaces and harder to deal with, when the drum machine is 4m behind the voice generator there's not much to worry about, if there is one foot between them you have a problem. A surgical sidechain management could deal with it but you sure don't want to do so for live performances, that kind of things you do by software when the signal is already recorded with tons of dirt.

totoxraymond said:
The correlation idea reminds me of Lemmy Kilmister microphone. Basically 2 sm57 side by side supposed to be out of phase. Lemmy had to sing very close to one mic for it to work. This allowed them to get very loud sound on stage.
Click to expand...
I don't know how that worked, it probably isn't just that, LF will keep canceling out till the 2 mics are too far away and just an inch would generate all sort of trouble over 5kHz and not cancel any signal out, maybe they was just triggering the gate with a filtered version of some combination of both mics, in which case is quite similar to what I suggested but way simpler implementation.

JS
 
joaquins said:
  A JCM800 or a young drum player can easily trigger a gate set to open with the singer, this leaking problems are worse on small spaces and harder to deal with, when the drum machine is 4m behind the voice generator there's not much to worry about, if there is one foot between them you have a problem. A surgical sidechain management could deal with it but you sure don't want to do so for live performances, that kind of things you do by software when the signal is already recorded with tons of dirt.
Click to expand...
One way this is dealt with is EQing the side chain of the noise gate to preferentially enhance or reject sounds. Noise gates like to KISS so simplest I've seen is a single tilt knob per channel that alternately boosts lows while dipping highs, or vice versa.
I don't know how that worked, it probably isn't just that, LF will keep canceling out till the 2 mics are too far away and just an inch would generate all sort of trouble over 5kHz and not cancel any signal out, maybe they was just triggering the gate with a filtered version of some combination of both mics, in which case is quite similar to what I suggested but way simpler implementation.

JS
Click to expand...
A trick used in premium noise gates is to add some delay so we can look-ahead to get a high threshold gate opened in time without cutting off the leading edge of sounds.
======

I got a patent for a gimmick in a noise gate I designed while at Peavey for live use. My concern there was how high thresholds set to work during live performance levels could cut off vocalists trying to patter conversationally between songs using normal speech levels. This special gate dedicated one smart gate channel to the vocalist, and insured that his gate was open, if all other gates were closed. This facilitated a relatively high threshold  for singing when the stage wash was loudest, while accommodating easy conversational speech levels when the stage was quiet.

JR

PS: Those who can do, those who can't teach. (those who can't teach criticize.) 8)
 
totoxraymond said:
The correlation idea reminds me of Lemmy Kilmister microphone. Basically 2 sm57 side by side supposed to be out of phase. Lemmy had to sing very close to one mic for it to work. This allowed them to get very loud sound on stage.
Click to expand...

That was also how the Grateful Dead "dealt" with having the Wall of Sound PA behind the singers: matched mics with inverted polarity to cancel the far field, and the singers had to be right on one of the two mics for it to work. Of course, this issue was the least of the problems with the Wall.
 
joaquins said:
What is known about something like this? Any project already chewed around?
Click to expand...

I mix live shows for a rock band whose lead singer has a tendency to sing quietly and also back off of the mic. I solve the problem the old-fashioned way: I use the faders. That's why consoles have them, right?

I know the songs well enough to be able to pull down his fader maybe 10 dB between phrases. And that's enough attenuation to make the stage wash picked up by the mic inaudible.  When he backs up to play a guitar solo, I pull the fader down even more.  I do the same for the two background singers; those mics are only up when they are actually singing. I insert a compressor on the vocal channels, but they really only kick in when they lean in on it.

So what's needed here is less technology and more skill in the hands of the person at the console.
 
  I'm aiming for a little gizmo to do the trick, mentioned that to a number of sound engineers and the interest is there. The correlation approach is too much for this but interesting as exercise, probably not as a comercial product as the processing power and ADCs required is likely to be too much for a tiny µC to deal with.

  JR, just to be clear, when I said simpler implementation I meant I was overcomplicating it rather than criticize the alternative...

  Andy, I'm sure you are aware that not in every situation you are able to do so, working with a band isn't the same that working on a venue with 10 different bands in one night, or on the stage where you are probably doing more than just setting monitor mixes, situations where this kind of automation is quite handy.

  Thanks for the insights, I guess I should get some IR and ultra sonic sensors and start testing out, at least to see if it's viable to do just with any of those.

JS
 
joaquins said:
  Thanks for the insights, I guess I should get some IR and ultra sonic sensors and start testing out, at least to see if it's viable to do just with any of those.

JS
Click to expand...
There have been people doing this for decades, I am not aware of any with wide commercial success.  Perhaps you can find one to look at what they did.

JR
 
JohnRoberts said:
There have been people doing this for decades, I am not aware of any with wide commercial success.  Perhaps you can find one to look at what they did.

JR
Click to expand...

Never seen one around here, I guess that drives the curiosity...

There's one I've seen a couple of times (in pictures) clipped on top of the mic, looks like a car radar detector but simpler, don't know the name though.

JS
 
what about a bad breath detector? bands usually do not have good dental plans,
you could use a CO2 sniffer in conjunction with a Carbon Monoxide detector,

or maybe an alcohol detector,

maybe a heat sensor from a motion detector,

or make the singer wear steel soled shoes, energize the mic grill with 10 volts AC , or 100 if it is Lemmy, install a GFI set to 30 ma with a NC relay in series with the XLR feed,

or hire a FOR geek,
 
totoxraymond said:
The correlation idea reminds me of Lemmy Kilmister microphone. Basically 2 sm57 side by side supposed to be out of phase. Lemmy had to sing very close to one mic for it to work. This allowed them to get very loud sound on stage.
Click to expand...
It's an old trick; it doesn't work as good as one would think at first sight. It's the basic principle behing noise-cancelling microphones. There's a big compromise between effective frequency response and feedback reduction.
 
Andy Peters said:
I mix live shows for a rock band whose lead singer has a tendency to sing quietly and also back off of the mic. I solve the problem the old-fashioned way: I use the faders. That's why consoles have them, right?

I know the songs well enough to be able to pull down his fader maybe 10 dB between phrases. And that's enough attenuation to make the stage wash picked up by the mic inaudible.  When he backs up to play a guitar solo, I pull the fader down even more.  I do the same for the two background singers; those mics are only up when they are actually singing. I insert a compressor on the vocal channels, but they really only kick in when they lean in on it.

So what's needed here is less technology and more skill in the hands of the person at the console.
Click to expand...
There is a number of situations where no one is in charge of sound. The system is set-up at the beginning of the gig and is left untouched till the end.
I play regularly in a club where the mixer is, on purpose, out-of-reach of the musicians, so whatever settings you end up with at soundcheck, you have for the rest of the night.
I use three tc electronics Perform-V (three lead singers and two BG vox in my band), so I have some control over the sound, and the feedback killer is not the less useful feature. There's also a noise-gate, but I just can't make it to do anything useful.
Don't think it's a particular of the Old Continent; I play often in New Orleans and it's the same. I mean, there's a guy coming, setting up the system, when he's finished he moves to another club and does the same. I guess he does it for 4 or 5 different bars/clubs.
 
joaquins said:
  Andy, I'm sure you are aware that not in every situation you are able to do so, working with a band isn't the same that working on a venue with 10 different bands in one night, or on the stage where you are probably doing more than just setting monitor mixes, situations where this kind of automation is quite handy.
Click to expand...

I understand. In the situations you describe, you have bigger problems.  The multi-band night at the club, like CBGB used to do before it shut down? Your band already has two strikes against it. Of course the mix person isn't going to give the care he'd give if he was mixing only one band. And assuming you had the magic gizmo you describe, do you have time to set it up during the changeover?

Over the years, I've tried various methods to automatically bring down the level of a vocal mic when there is no singing. A gate,  with the range set to 10 dB or so attenuation, seemed to be the most effective. But even then, you can spend the entire set tweaking it to get it right. This is especially true in a small club where the stage wash is a problem.

I suppose you could try to implement the Dan Dugan automixing scheme, which the corporate mix people use to great effect when dealing with a table full of talking heads who have no idea how to work a microphone. But those situations don't have stage wash.
 
Andy Peters said:
I understand. In the situations you describe, you have bigger problems.  The multi-band night at the club, like CBGB used to do before it shut down? Your band already has two strikes against it. Of course the mix person isn't going to give the care he'd give if he was mixing only one band. And assuming you had the magic gizmo you describe, do you have time to set it up during the changeover?

Over the years, I've tried various methods to automatically bring down the level of a vocal mic when there is no singing. A gate,  with the range set to 10 dB or so attenuation, seemed to be the most effective. But even then, you can spend the entire set tweaking it to get it right. This is especially true in a small club where the stage wash is a problem.

I suppose you could try to implement the Dan Dugan automixing scheme, which the corporate mix people use to great effect when dealing with a table full of talking heads who have no idea how to work a microphone. But those situations don't have stage wash.
Click to expand...
I suspect Dan has been trying to make his AM work for band use, and despite much effort over the years has not received much success. In the early days it was way too expensive to be practical.

Peavey included analog AM inside some dedicated church consoles where is seems a little more practical.

Now AM is almost free inside digital mixers, but if you think about how it works mixing music is not about literal gain sharing .

I expect smart automatic music mixing to evolve over time, but as I have long been saying, the bands that can afford the cost and time to develop this are not interested, the low end musicians who could benefit are not willing to pay the price premium.

JR
 

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