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Outdoor Noise Cancellation Pa System
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StarfishMusic
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#1
28th September 2009
Old 28th September 2009
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Talking Outdoor Noise Cancellation Pa System

Ok heres the Dilemna: Outdoor Teakee bar and restaurant is located across about 1/4 mile across water from very expensive waterfront homes. Because the people are complaining, the cops have to enact the noise ordinance stuff on them and they are forced to close at 10pm. They also have been under threats for fines even before then etc.

I am friends with the cops in charge of this and I can have them give my number to the owners if this idea is feasible. If they have no more noise complaints from across the water they can basically stay open till much later have bigger festivities and bands and make tons more money. Of course if I can make this happen it will be worth my while I'm sure.

Here's what Im thinking, everyone here knows that reversing the phase of a signal and playing it back with the original creates a cancellation that in a perfect (software) world completelly nulls the orignal audio. I simply need to reduce the DB levels across the water to an acceptable number. If I basically make a giant set of bose noise cancelling headphones will it work on such a large scale? I'm thinking loudspeakers that each have a microphone placed somwhere behind them with the phase flipped. I'm sure It's much more important to cancel lows so I may have to add some subwoofers with kick drum mics and or crossovers to the (anti) mix.

I have read on the net about industrial plants doing things like this to quite giant fan noise, but that is much more of a tone. Im also pretty sure I heard about long ago stealth military helicopters that have a whisper mode speaker that reduces the blade noise.
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#2
28th September 2009
Old 28th September 2009
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#3
28th September 2009
Old 28th September 2009
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Wow.. that makes my head explode a little...!

Is a time aligned phase revered signal from the the music played indoors, piped out to an outdoor, weather proofed (?) speaker array going to do any good..?

Seems like a stretch to expect it to..

Interesting question..

Industrial scale phase reversal!

I think I will phone up a chum that installs club PA's for a living and ask him if he has heard of such a thing..

OK - I just called, here is his experienced overview..

Outdoor locations are very difficult to manage!
Make sure NO speakers are facing the waterfront properties!
Try using 'localized baffles' pointing the sound back to the diners / clubbers but not angled so it bounces back off a front wall of the club - back across the water..!
Try to limit the bass levels?
Try temporary enclosures / drapes during one off gigs..?
What are they complaining about? Bass? if it is - an anti phase set up MAY work - but its a long shot if it is hi mid / hi frequency its bad news - as there is no way to phase reverse outdoor club noise that is of "varying frequency" (ie music not a hum or drone like that from engineering works)
My favorite tip of his is this - get the PA speakers AS CLOSE TO the diners / patrons as possible. Then it doesn't have to be so loud! He calls this a 'distributed; system. Try hanging a small set of speakers above EVERY table!
He says the bar owners need to 'get inventive' with how they distribute sound.. And cites that as their only chance..

Speaking with him gave me a few (possibly obvious) ideas..

Plant a hedgerow.. along the water front - hide baffles angled up to direct sound over the club building in the hedges?
always set up band and its PA pointing away from water and the opposite properties?
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28th September 2009
Old 28th September 2009
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thanks for your response jules. It is a live band on a stage outdoors not indoors, and it does face the water. Bass is way less directional and is what I just would have to reduce because the ordinance goes by decibel level. Im sure its mostly bass frequncies making it across the water and into homes. The hedgegrow would have to contain some serious owens corning lol however it would still block the water. This is not a polite little restaurant where everyone sits neatly at tables. I forget that in florida everyone knows what an outdoor teakee bar is but probably not too many other places. Picture the movie "Cocktail" with Tom Cruise.
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28th September 2009
Old 28th September 2009
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Don't think you'd have much luck with some crazy noise cancellation system. There would be no way to control the sound past the audience, especially outside.

All of Jules/his friends ideas are the obvious things to try. Like turn the stage round.
I'd think a lake would make a nice backdrop.

Or the smaller distributed system.
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28th September 2009
Old 28th September 2009
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Too many constantly-changing variables for it to work reliably - changing wind direction and speed, changing barometric pressure, etc. - and even if it did work in a completely theoretical controlled environment, it would only work for one spot, not the entire row of houses spread across the far riverbank. It would actually make it worse in some spots - comb-filtering canceling in some spots, reinforcing in others, and constantly changing based on position, environmental factors, etc.

Live band playing outdoors is going to be a tough one, and 1/4 mile is only a few city blocks.

If it's "solvable", it'll be with many small speakers distributed around the listening area, no "stacks", and no live acoustic drums. Jazz combos with brushes, maybe.

A 50-foot cinder-block wall would work, but I'll bet seeing the river from the outdoor seating area is as much of a selling point for the bar as it is for the houses across the river.

People with any sort of "waterfront property" are not going to be very amenable to even being able to overhear faint strains of the music with all their windows open, I'm afraid.

Around here, there's a ludicrously low boat speed limit because people the McMansion people on the shores complained about the noise from each other's boats.
#7
29th September 2009
Old 29th September 2009
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How is that the stage faces the water?

Seems like an oversight in planning.

Stage facing water to me means PA stacks facing water = noise pollution disaster

Can it be reversed? Turned around?
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29th September 2009
Old 29th September 2009
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the Hypersonic Sound System can direct a focused sound 'beam' at targets as narrow as an individual in a crowd. Someone could literally send you an audible PM with one of these.


This is the same technology as used at higher power levels on the LRAD 'sound cannons' used on ships to deter terrorists, Somali pirates and the like.

These devices are not cheap compared to normal speakers, and as Jules points out, there are too many variables to expect any kind of reliable cancellation at a distance, but they could conceivably be used to "focus" the sound you are sending to your audience. In principle at least, only your patrons would hear the sound. I don't know what the sound quality is like. They don't look like they do much bass.

Considering the millions that municipalities spend on barriers for highways and so on, if noise cancellation actually worked in the open air, you can bet it would already be available off-the-shelf.

Realistically, your best bet is to turn the band around and point them into something soft. Trees are good. I used to live in the woods, and when we had a jam, a quarter of a mile away, you couldn't hear it. Well maybe you could still hear the timbales.

The real question is how much 'over' the local limit are you when the sound reaches the neighbors across the lake. You don't have to satisfy them, you only have to satisfy the law.

Robert Heinlein once wrote about a future society which got by on only two laws:

1. You mustn't annoy other people
2. If you are other people, you mustn't be too easily annoyed.
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29th September 2009
Old 29th September 2009
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There are some companies offering PA system components that do what you want.

I just finished installing a D&B line array system with the CSA or "cardiod subwoofer array". This is basically what you want - it has forward and rear firing drivers. The rear-firing drivers cancel bass on the back side of the subs. It is amazing how little bass there is right behind the subs! It also makes things very punchy on the front side, which is what D&B was going for I'm sure. (D&B speakers are in the top tier of quality and price, like Meyer Sound, L'Acoustics, etc.)

Product link

Or for higher frequencies, there's a new company that has a line array speaker system that uses the LRAD-type technology. It's called K-Array and is distributed by Sennheiser in the US. I haven't heard it myself, but reports are good. It's a "dipole" design (like figure 8), where lots of sound comes out the front and some out the rear but very little from the sides. Perhaps these could be oriented so the sides face the big houses?

I don't know about the matching K-Array subwoofers, their subs look conventional and not noise-cancelling, and I can't seem to find anything about that on their website. The K-Array speakers are pricey.

K-Array
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30th September 2009
Old 30th September 2009
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Quote:
Originally Posted by Jeff D. View Post
There are some companies offering PA system components that do what you want.

I just finished installing a D&B line array system with the CSA or "cardiod subwoofer array". This is basically what you want - it has forward and rear firing drivers. The rear-firing drivers cancel bass on the back side of the subs. It is amazing how little bass there is right behind the subs! It also makes things very punchy on the front side, which is what D&B was going for I'm sure. (D&B speakers are in the top tier of quality and price, like Meyer Sound, L'Acoustics, etc.)

Product link

Or for higher frequencies, there's a new company that has a line array speaker system that uses the LRAD-type technology. It's called K-Array and is distributed by Sennheiser in the US. I haven't heard it myself, but reports are good. It's a "dipole" design (like figure 8), where lots of sound comes out the front and some out the rear but very little from the sides. Perhaps these could be oriented so the sides face the big houses?

I don't know about the matching K-Array subwoofers, their subs look conventional and not noise-cancelling, and I can't seem to find anything about that on their website. The K-Array speakers are pricey.

K-Array
YES the "CSA" THATS IT! I knew a noise cancellation system theoretically would work, I just didn't realize how controlled the environment would have to be and how many other variables would come in to play. But cancelling it in a controlled manner from the source itself is brilliant and I'm sure involves some crazy math that Is taken care of right within the subwoofer. That doesn't help other loud frequencies but I'm pretty sure it was just the bass that I just had to worry about. Give them a fairly high crossover point and make the bass player play direct or low volume from their cabs, maybe a baffle behind the drummer and its done. Of course the stage would have to be moved, but for staying open 4 or more hours a night I'm sure they would. Thanks so much for everyones (except that first guys lol) responses.
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30th September 2009
Old 30th September 2009
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Do post updates if you try this - it'd be interesting to know if this actually works!
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30th September 2009
Old 30th September 2009
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as music can be great it can be extremely annoying
its nice to see people making music/ playing to attempt to do it in
a non selfish non annoying manner


first organizing the sound waves,
barrier kinda like a sound wall around the drummer but still open
then you do some very careful timing and possibly many speakers
around where you dont want noise

in theory it seems simple your just reversing sound waves but then
you have to deal many resonant freq different materials , big spaces and time and temp humidity all kinds of stuff

Its possible though

the hypersonic would kind of work only they are missing low end and a very narrow field of sound

I have wanted a hypersonic sound disco ball for years



you could always just plant a bunch of low volume speakers around the yard and build a special thing for the drums build a sound Prof little room deal to run all the guitar and bass amps
get a weather Prof mixer

have different mixed spots all around the yard
so you can walk around the yard and it would sound different at
different parts of the yard different mixes

sound travels really good over water so
a low volume many speaker system
and a bunch of mixed spots would take the buttery cake
one side of the yard has a totally different mix
since it would be low level volume you could have many
stereo and quad mixes pending on space
if done right could cancel noise

could use the water , you turn the lake into a speaker
fish would not like you but by the time sound got across the lake
it might work just a little complicated

some heavy duty fog machines
and some type of speaker bouyies
I think once the sound is on the water
you would have a better chance of canceling it
at least it would be constant

I guess for horns you could make a sound trap deal to blow into
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30th September 2009
Old 30th September 2009
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Quote:
Originally Posted by Jeff D. View Post
There are some companies offering PA system components that do what you want.

I just finished installing a D&B line array system with the CSA or "cardiod subwoofer array".

The Nexo Geo - T and S line arrays offer the same kinda thing. well worth the money in these kinda setups. and as anothe poster mentioned, it dont have to be silent at the other side of the water....


find out what the LEGAL limit at the edge of the property (from memory the high water level) is and aim to come in under that... that way you aint breaking the law, and if you aint breaking the law, well there isnt really a problem
#14
16th July 2012
Old 16th July 2012
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Id say try an N-type array with the PA facing away from the water.
I think N-type is the one i mean, using identical subwoofers in 2 parallel lines.

Considering the problematic frequencies and their relative wavelengths, you can target these specific frequencies by placing the subs certain distances (half the wavelength of the Freq you wish to minimise).

Typically the sort of thing used as festivals where theres lots of bass and some directionality is wanted.

Might be worth downloading D&B array calc or something similar depending on your PA.
#15
18th July 2012
Old 18th July 2012
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I’m sure the problem has been solved by now but I've been working at an acoustics firm in NYC for the past few months and thought I might be able to offer some useful advice for anyone who comes across this thread.

Someone stated earlier that you don't have to please the neighbors you just have to keep it legal, which is true with some exceptions. Most noise codes are intentionally written to be terribly ambiguous and when they do state a number, 45dB(A) in NYC, it’s often untenable for most locations. In the suburban context, if a guy mows his lawn he’s easily 30dB(A) over the ordinance. In the city, many of the places I’ve visited are around 20dB(A) over continuously, and in Florida think about the theme parks and the bars- they’re all over. However, we also see the inverse where there is barely a violation (often none at all) and we are out there conducting tests because someone thought they heard someone doing something and they could swear that it was coming from right over there and it happens all night but we’d really have to be there. Many noise ordinances are enforced on a complaint basis, so if no one complains you aren’t breaking the ordinance. It seems obvious but it is a very important point. I’ve heard stories of your exact situation specifically in Florida and what ended up happening is that they put a limiter on the system right before you hit the amps and when the people across the lake complain the cops come out and verify that the PA is where it should be and everyone goes home unhappy because the neighbors are still irked and the bar can’t get above 45dB(A), essentially a loud acoustic guitar. So before you fight the legal battle you might try changing the neighbors mind’s by changing the performance program to quieter music styles and by flipping the stage around. After several months the neighbors will believe that their complaints have been heard and that the problem has been remedied thus making them less sensitive to the issue. Once this occurs you can gradually go back to a reasonable (read the noise codes, you’ll see that word frequently) level. That Robert Heinlein quote posted by joeq is particularly salient here. In my experience most people who complain just want someone to acknowledge they’re not crazy. My recommendations are practical fixes and a neighborly attitude first, then (only if you have to) go the legal route.
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