Does this device exist? (monitor audio levels and adjust an amplifier real time)

Discussion in 'Electronics Resources' started by Tom Pendergast, Sep 27, 2014.

  1. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    Input: microphone level audio
    Output: control signal for Voltage Controlled Amplifier.

    This device will (real time) monitor audio levels in a room. Will keep track of the quiet levels and constantly control a VCA to keep the target level at +XdB above that quiet level.

    Intended use: Monitor the ambient sound in a restaurant or bar, keep the house audio system (jukebox, TV sound) playing at a preset level above that "quiet" level. As the place fills up conversation levels increase, automatically turn up the jukebox, and vice versa. The dead time between songs, commercials etc would create the valleys in the monitored signal.

    Would really prefer to buy it, but would consider building it if need be. Realize it could (should) be done with software on a PC. Have searched (Google) for it but nothing is showing up.
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I'd avoid that restaurant or bar at all costs. One annoyance that I cannot stand is places where the music is too loud. A system that raised the loudness of the music as we spoke would drive me crazy!
     
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  3. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    Wel-l-l-l-l ... Looking at it from the other side, we're tired of people playing the jukebox and then some miserable geezer at the bar complains to the barmaid who turns it down so low that the person with the $5 in the jukebox is demanding a refund. No hands policy, the level stays whatever dB above the ambient sound, end of story. :)
     
  4. rogs

    Active Member

    Aug 28, 2009
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    Not that simple a thing to do. It will try to 'chase it's own tail', if you attempt to sample continuously.....The ambient level goes up....music goes up. Ambient sensor detects higher ambient (which now includes louder music)... and turns the music up.. and so on.. just gets louder and louder!

    You either need to 'sample and hold' the ambient level- during 'gaps' in the music of course - and use that to set the next 'gain' level setting ....(I guess that's what you mean by the 'valleys'?)
    Or you need to 'compare' the ambient sound against the generated music signal, to decide what is ambient and what is music ... and that's not an easy task at all.

    The first option is easier, but I'm not sure if it's available as an 'off the shelf' device for 'real time' operation..... maybe someone has already come across either a commercial system , or has developed one as an amateur experiment?
    (I did some work on such an idea several years ago, but the 'marketing' folk decided to pull the plug fairly early on into the project, so it never got very far...I may have some notes somewhere I can dig out, if no one can suggest a commercial device.. they never were that complete though...)
     
    Last edited: Sep 27, 2014
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    off the shelf things are available for this, search the Publc Address suppliers. I a home now, but I will check back monday with a model number and maker.
     
  6. #12

    Expert

    Nov 30, 2010
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    I think that sampling in the valleys is sufficient. That is, adjusting the loudness every 3 or 4 minutes will probably work.
     
  7. rogs

    Active Member

    Aug 28, 2009
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    As alfacliff suggests, there are commercial units available. This TOA unit seems typical : http://www.toaelectronics.com/products/dp-l2.html

    It's not cheap though!:(.....

    This one looks to be better priced...http://www.bhphotovideo.com/c/produ...mmunications_ANS501_ANS501_Ambient_Noise.html

    ... although as it's for paging systems, it may not sense that music is being played.....

    You will also need to consider where in the existing system this is going to fit?.......you mention a jukebox and TV sound. If these are separate 'standalone' units , with their own integral power amps and loudspeakers, how do you intend to introduce gain control into their signal paths?....

    Or is it all part of an installed system, with separate power amps feeding installed loudspeakers...so that you already have a single overall volume control over all sound sources?...
     
    Last edited: Sep 28, 2014
  8. BR-549

    Well-Known Member

    Sep 22, 2013
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    In the summer of 2001 I had the experience of driving a ford focus that was not equipped with air conditioning. This was in city traffic with the windows down all the time. The stock am/fm/cd player was superb. It would automatically adjust volume to the background noise and it worked perfect. It spoiled me....what a great feature.
    I don't know exactly how it did it. A monitoring microphone on the dash?.........and/or...only listening to small band of frequencies?(like listening for rumble?)......or maybe not a microphone......but maybe monitoring vibration?
    It really worked perfectly. Most impressive. I understand why the OP wants this.
     
  9. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    You either need to 'sample and hold' the ambient level- during 'gaps' in the music of course - and use that to set the next 'gain' level setting ....(I guess that's what you mean by the 'valleys'?)

    Exactly. It's going to get a level between songs on the jukebox which mat be 5 seconds, 5 minutes or 5 hours. I want to make the process concentrate on sampling that portion and using it to adjust a Voltage Controlled Amp. If 10 people wander in and start talking, clanking glasses etc, the "quiet" level will be less quiet, my "average" will go up, and the output voltage of my circuit will adjust the VCA to play the Jukebox louder. All sampling / adjusting to be -gradual-, of course.
     
  10. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    Yes! I'm thinking it would need to sample and hold the lowest peaks, that can't be too hard to accomplish? Then apply some math and take an average every few minutes and change its output control voltage gradually (buffer the change level somehow so it doesn't "jump".
     
  11. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    You will also need to consider where in the existing system this is going to fit?.......you mention a jukebox and TV sound. If these are separate 'standalone' units , with their own integral power amps and loudspeakers, how do you intend to introduce gain control into their signal paths?....

    Or is it all part of an installed system, with separate power amps feeding installed loudspeakers...so that you already have a single overall volume control over all sound sources?...


    Thanks for the product tips, I'll check them out as soon as I answer here:

    No, yes, yes.

    All line level inputs will go through a Shure mixer that has auto override for the Jukebox input. Other sources are TV sound, remote plug-in connections (paralleled) where a DJ or band could feed line level in, a Push To Talk mic for the kitchen to page finished orders (will override EVERYTHING) and wired and wireless mic feeds to a separate mic mixer. The Auto Jukebox Override will be defeated by pausing the jukebox when we have a band playing, important sports event on TV, etc. It's not really as chaotic as it sounds!

    The master output of the Shure is going to go to a Voltage Controlled Amp. That VCA will go to a DA and feed 4 power amps for 4 zone coverage of the facility. The VCA will have a "Trim" slider behind the bar where the barkeep will be able to do exactly that, make a MINOR adjustment to the overall level, no matter what is playing. Somewhere in that VCA control chain I want to integrate this magic level control which will turn EVERYthing up or down depending on how noisy the bar is. I realize it's going to take some serious tweeking to get it set up, but I think it will be worth the effort.

    I hope that helps.
     
  12. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    ... It would automatically adjust volume to the background noise and it worked perfect. It spoiled me....what a great feature.
    I don't know exactly how it did it. A monitoring microphone on the dash?....It really worked perfectly. Most impressive. I understand why the OP wants this.


    Rogs mentioned it above, about "comparing the ambient sound against the generated music signal", and I think that's what might have been happening. "Noise cancelling" as it were. If you mic the ambient sound and compare it to the pure electronic version coming from the radio, you can generate a "difference" signal that Ford was somehow using to control the gain on the radio amp.

    The more I think of it, that might be a possible solution for my situation. Thanks for the brain ping, you got me thinking about it now!
     
  13. Lestraveled

    Well-Known Member

    May 19, 2014
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    I think you are missing a human response issue here. People will try to talk above the music level and when the music stops for a moment the talking volume will not instantly change. If you sample in the short dead time between songs you will get an artificially high level. Remember, the music level drives how loud people talk. This factor make for an unstable control loop.
     
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  14. alfacliff

    Well-Known Member

    Dec 13, 2013
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    since it is possable to use digital signal signal processing to sample engine sounds and invert them to cancel engine noise, why isnt it possable to do the same with ambient noise level, invert, and add to cancel, or even to get an average noise level?
     
  15. Lestraveled

    Well-Known Member

    May 19, 2014
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    Because the engine doesn't get louder when the radio gets louder.

    I am not saying it can not be done. I am saying it will not be a simple control loop.
     
  16. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    That's the solution. Issue your customers with headsets to cancel the jukebox noise :).
    I'm with Djfantasi (post #2) on this, and tend to avoid restaurants with muzak and jukeboxes.
     
  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the engine does change sound both in loudness and pitch with engine load, that is used to vary the inverted engine sound to ad to the non inverted sound to cancel the engine sound. like picking up the room noise and using it to vary the music sound.
    a restaraunt I was in with my family last weekend had two screaming kids right behind us. I asked the waitress on the way out if it wopuld be ok to bring in a boat horn next time.
     
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  18. Lestraveled

    Well-Known Member

    May 19, 2014
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    A human makes these kinds of evaluations much better than a computer. You can spend money and time to build an electronic widget that is almost as good as your bartender and still have the old geezer complaining that the music is too loud. It is just what geezers do.

    Maybe you can build a geezer filter........
     
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  19. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    The human will side with the geezer because the geezer is sitting there 6 days a week nursing 2 beers and thinking they're in their living room. The casual customer who comes in once a month and wants to play some music doesn't have a chance. That's exactly why the human element has to be taken out of it.
     
  20. Tom Pendergast

    Thread Starter New Member

    Sep 27, 2014
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    I wish you two luck in finding an establishment that mimics your living room, some place where you can sit at the bar and watch Wheel of Fortune in peace and quiet.
     
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