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Author Topic: any input about electronic variable acoustic systems  (Read 9349 times)

Karl P(eterson)

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Re: any input about electronic variable acoustic systems
« Reply #10 on: March 24, 2005, 08:12:28 AM »

While I deeply respect you Tom, is there something about your comment which makes it specific to "anti-reverb" ?

I ask this question because I have seen in commercial use a number of noise masking systems which range from "intelligent" white noise generators (which work pretty damn well adapting to the enviroment). All the way up to full blown maskers which stick halve a dozen meyer-esqe boxes "implanted" into the room, a 25'000 computer and a few nice measurement mics inside and right arround the source as well as a few in the room.

All in all its a 50~60'000 dollar setup and it can only mask up to two sources (I believe) but it was amazingly efective. I saw this system in use in the boardroom-s- of UPS World headquarters a number of years back, and have since seen them in a variety of other lawyers offices and other such places. They have always worked exceedingly well.

Care to clarify?

Karl P
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Tom Young

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Re: any input about electronic variable acoustic systems
« Reply #11 on: March 24, 2005, 08:49:00 AM »

Sure.

We are talking two completely different animals here.

Masking is not cancelling.  

Masking works by introducing random noise which defocuses the ear-brain from hearing what we don't want folks to hear. Typically this is outside of a doctor's or therapist's office where the private conversations would be heard by folks in the waiting room or another office. When we introduce white or pink noise (random noise) at a loud enough level (doeasn't need to be very loud at all, actually) the folks who are exposed to the noise do not hear the conversations, or at least cannot hear them well enough to understand them.  

There is lots going on here.  If it was music we were trying to make "not audible", random noise would not work because music has a rhythmic and repetitve character that we can discern through the noise masking energy.  But in order for us to understand conversation, we need lots of aural cues which are masked by random noise, in this case, and which are also masked by long/late reflections or too-long & loud reverberance in the case of a space with poor acoustics and therefore low intelligibility. Note that you will still faintly detect that human voices are speaking with a noise-masking system or in a low-intelligibility aural experience. But you will not understand most or all of the words being spoken.  This effect is not effected by listener's position because there is no arrival tme relationship between the effect of the random noise and your ears.

Understand why this is not akin to noise cancelling ?

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Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
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Al Zara

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Re: any input about electronic variable acoustic systems
« Reply #12 on: March 24, 2005, 09:02:37 AM »

I think we are comparing apples to oranges.
Like tom said masking is just what it does, it masks.
We were discussing the probobility of introducing the inverse of the room anomolies back in to cancel them out & like explained earlier when dealing with music that is not possible yet...
imagine beeing able to fix an acustical nightmare with out treating the walls.
Maybe in our lifetime we will see this!
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Aaron J. Percy

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my location
« Reply #13 on: March 24, 2005, 09:37:58 AM »

Tom Young wrote on Wed, 23 March 2005 15:36

Where are you located ?

Maybe I can point you to an installed electronic enhancement system.



Baltimore, MD.  This whole thing has become very interesting to me.  I am looking in to the possibility of reducing the standing waves in our current room to make it more ready for an electronic acoustic system.
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Peace,  Aaron

Tom Young

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Re: my location
« Reply #14 on: March 24, 2005, 09:52:47 AM »

Well, as we speak there is a LARES system designed for the Air Force band being commissioned in DC. But it's too late for me to try to hit them up for you to go hear/see it.

Sometime in the not too distant future I will hopefully be doing a LARES system in DC myself. Stay in touch and I'll let you know when that happens.

I'll ask my friends at LARES what else they may have in your area.
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Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com

Karl P(eterson)

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Re: any input about electronic variable acoustic systems
« Reply #15 on: March 24, 2005, 10:22:19 AM »

I perfectly understand the differences between masking and canceling, and understand why "noise cans" work how they do with random white noise. Which is the very reason why I mentioned "intelligent" white noise (which really doesn't apply here, I understand) but more importantly the second system (which I was wrong to call a masking system, as it really is a canceling system).

How it works is that it reads (based on the measurement mics) the sound from whatever the noise source is, and generates an off phase signal which is then dsp processed and put out through the different speakers in the room in some proprietary way so as to cancel the noise being emanated from whatever it is that is making the noise.

I do not see how this is different from what they want to do in the "Reduction" thread, although arguably it would be exceedingly difficult to use one for "anti acoustical badness" as you would technically need a system in every single acoustical reflection point.

That is, of course, unless some amazingly complex signal dsp and a distributed system of advanced digital steerable arrays was conceived which could account for every reflection spot in the room, and could fire sound waves at each location (or groups of) in exactly the right time and phase to cancel the waves.

Anyone up for a science project.

Karl "But seriously, I don't get how the system is not a canceling system" P
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Al Zara

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Re: any input about electronic variable acoustic systems
« Reply #16 on: March 24, 2005, 11:54:15 AM »

Have any links for that pruduct... or is it proprietary?
i'd like to check that out.

Sort of like "The cone Of silance 99"
"Missed it by that much"
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Karl P(eterson)

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Re: any input about electronic variable acoustic systems
« Reply #17 on: March 24, 2005, 12:38:39 PM »

I do not remember who's product this is (it was an unbranded system) or even the installer. It has been a good 5 years since I first saw it at UPS, I have heard of it being installed (my father is in a architectural woodworking firm) in a few lawyers offices. I do remember it was highly proprietary (security system on the dsp/computer box, everything unbranded) and that it cost a ton (north of 50 for one source, probably more for 2) There was extensive consideration of the acoustics of the room, and a ton of data being held by the system (dsp) I believe they were measuring and putting in information for a good three or four days.

I can certainly understand why it doesn't make sense that it would work, I probably wouldn't believe it had I not seen it and  believed it.

I believe ups does work with lockheed on certain aspects (technological) of there buisness, is this possibly one of there products?

Karl P
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Brian Bolly

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Re: my location
« Reply #18 on: March 24, 2005, 01:26:46 PM »

There's an old Jaffe ERES system in St John's Episcopal Church in Washington, D.C. right across from the White House.  The install is from around 1990, so I would think its one of the earlier generations of the system.  This was the first one I'd ever knowingly heard and it was pretty cool, considering the natural acoustics of the (small) room.

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Al Zara

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Re: any input about electronic variable acoustic systems
« Reply #19 on: March 24, 2005, 01:49:11 PM »

Thanks for getting back to me!
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