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Sound Cancellation Devices?
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l008com
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Sep 21, 2011, 11:12 PM
 
Does anyone make stand-alone "black boxes" that you can hook up to a mic, and a pair of speakers, to use as a noise cancellation device?

I posted this to my regular marine forum but I figured I'd post it here too.
My boat is an outboard and it's kind loud. After a few hours, it really makes your head pound. I just installed two speakers, one on either side of the motor, to eventually hook up to a stereo. But then I realized, this is the perfect setup for noise cancellation. I don't need silence, just many fewer dBs. The noise is coming from just one direction, and the passengers are all sitting in just one other direction. Plus theres no echoing to speak of out at sea.

So what would be perfect would be a small box with built in amp and audio processor. You'd plug in a Mic that you'd mount on the windshield. Plus in power and speakers. Then if this device was really smart, you'd also plug in a pre-amp output from the stereo, to this device, so it could automatically filter out (not noise-cancel) music you have playing. And lastly, it would be nice if such a device could be smart enough to also filter out human vocal frequencies, so it wouldn't try to cancel out your speaking. Really, JUST the loud engine noise.

This isn't the most revolutionary idea in the world. In fact many cars have exactly this built in. Someone must make a stand-alone solution for this? Any thoughts, or ideas?
     
bstone
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Sep 21, 2011, 11:46 PM
 
Wait, you want to hook up a device that will broadcast a tone on the same wavelength as the boat engine and cancel out the sound? You do know that the engine from the motor is regularly changing so you'd have to have some way to adjust for it on the fly. Why not just use paddles or turn off the motor?
     
l008com  (op)
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Sep 22, 2011, 12:23 AM
 
I'm not looking for a tone generator. That's what the mic is for.
     
bstone
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Sep 22, 2011, 12:24 AM
 
Slow down there, boatman. I don't think you know what you're dealing with. Crossing the streams is a bad idea.
     
l008com  (op)
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Sep 22, 2011, 12:24 AM
 
Don't you remember? It was a bad idea until they actually did it, then it actually worked out pretty well.
     
MacNNUK
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Sep 22, 2011, 02:25 AM
 
I use my active noise reducing headphones in noisy environments, such as unplugged in an airplane, and neighbours burglars alarm, they are very effective at reducing background noise.

£20 / $35 a pair, bought them in Chicago actually !

Or even just earplugs ?
( Last edited by MacNNUK; Sep 22, 2011 at 03:12 AM. )

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l008com  (op)
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Sep 22, 2011, 02:27 AM
 
That's great, but wearing headphones while driving a boat is not very practical, and probably illegal.
     
Spheric Harlot
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Sep 22, 2011, 03:15 AM
 
Originally Posted by bstone View Post
Wait, you want to hook up a device that will broadcast a tone on the same wavelength as the boat engine and cancel out the sound? You do know that the engine from the motor is regularly changing so you'd have to have some way to adjust for it on the fly. Why not just use paddles or turn off the motor?
Active noise control - Wikipedia, the free encyclopedia

This works on headphones and to a certain degree in cars because the targets are fairly fixed relative to the speakers.

It's probably not feasible in an environment where people move around, because the moment you move two feet to the right, noise source and speaker are no longer aligned, and the phase cancellation effect shifts into addition, INCREASING the noise on certain frequencies.

For fixed positions, something like this is pretty simple to build using a programmable DSP/interface such as the Metric Halo Mobile I/O.
Hook up mic, add some hi-cut filtering, invert phase, adjust phase delay for maximum cancellation effect, pipe to speaker. Not a feasible solution for boating, though.
( Last edited by Spheric Harlot; Sep 22, 2011 at 03:23 AM. )
     
l008com  (op)
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Sep 22, 2011, 03:18 AM
 
Originally Posted by Spheric Harlot View Post
I didn't know this technology/phenomenon was a secret.
     
Spheric Harlot
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Sep 22, 2011, 03:30 AM
 
Originally Posted by l008com View Post
I didn't know this technology/phenomenon was a secret.
Neither did I, but bstone appeared to be unaware of it, so I posted a link (which, incidentally, includes a more detailed explanation for why this is difficult to achieve, but also mentions that it's used in marine applications — presumably to reduce vibration on the ship itself, though (rather than in the air).
     
l008com  (op)
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Sep 22, 2011, 03:36 AM
 
The people in the marine forum seemed to know nothing about it either.
It's perfect, at least for my particular application, because:
All the noise I want to cancel is coming from one direction, the motor.
All the ears that are to be in the reduced-noise zone, are coming from one direction, which is opposite the motor, the way the speakers are facing.
And on a boat, there will be very little echo from sound bouncing around. It's an open space with no objects nearby. It is an ideal environment for this technology.
As the sound moved forward from the engine, it would get to the speaker location, where the opposite phase sound would come from, and both sounds would move forward across everyone's ears. There's no resonating, echoing, bouncing, etc. And I'm not talking about putting a recording studio on my boat. If I could just tone down the intensity of the engine noise by 50%, that would be HUGE.
     
Spheric Harlot
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Sep 22, 2011, 03:53 AM
 
Will the ears be belted down, though, or will the be moving about? If the latter, there is pretty much nothing you can do. You *might* get decent reduction on the lower frequencies, but probably not enough to warrant the effort.

The other option is using ANC to reduce vibration to the vessel's frame itself. Effectively, that amounts to mounting a massive speaker to the boat itself. I'm pretty sure that needs to be designed into the boat from the start, and is probably not doable for less than five digits.
     
l008com  (op)
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Sep 22, 2011, 03:59 AM
 
Ears will be moving a little bit, but the speakers will always be straight back, and the engine will always be behind that, no matter where the ears in the boat move. Which is why I suspect with the right device (which I'm starting to think doesn't exist), this could be very effective.

It's a fiberglass vessel so vibration isn't an issue at all. It's an outboard, a large 3-cylender, 2-cycle, LOUD outboard. The only issue is sound. It's just so loud, that after a few hours, you really start to get a headache.
     
Doofy
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Sep 22, 2011, 07:18 AM
 
It'd be cheaper to buy a quieter outboard.
Also, IIRC from the horns thread, your boat is quite small and I don't think you'd have the space for the speakers needed to produce the low-end out-of-phase signal to counteract the outboard.
Been inclined to wander... off the beaten track.
That's where there's thunder... and the wind shouts back.
     
l008com  (op)
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Sep 22, 2011, 07:59 AM
 
Cheaper to spend $18,000 on a new motor vs playing sound through my speakers?
And what makes you think a pair of 6.5" speakers are not powerful enough? It's a 2-cycle engine, its not a low frequency type sound.
     
Doofy
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Sep 22, 2011, 08:49 AM
 
Good luck!
Been inclined to wander... off the beaten track.
That's where there's thunder... and the wind shouts back.
     
bstone
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Sep 22, 2011, 11:41 AM
 
There exists no technology that can cause a sound to become mute. None.
     
Spheric Harlot
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Sep 22, 2011, 11:57 AM
 
Originally Posted by l008com View Post
Cheaper to spend $18,000 on a new motor vs playing sound through my speakers?
And what makes you think a pair of 6.5" speakers are not powerful enough? It's a 2-cycle engine, its not a low frequency type sound.
I think you vastly overestimate the power and accuracy (and the relationship between the two) of loudspeakers, and vastly UNDERestimate the power output by your outboard motor.
     
Spheric Harlot
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Sep 22, 2011, 11:58 AM
 
Originally Posted by bstone View Post
There exists no technology that can cause a sound to become mute. None.
This is patently false.

There are limitations and many circumstances in which it won't work, the biggest issue being that it is usually an extremely localized phenomenon, but to say it doesn't exist is just flat-out wrong.
     
bstone
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Sep 22, 2011, 11:58 AM
 
Originally Posted by Spheric Harlot View Post
I think you vastly overestimate the power and accuracy (and the relationship between the two) of loudspeakers, and vastly UNDERestimate the power output by your outboard motor.
     
bstone
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Sep 22, 2011, 11:58 AM
 
Originally Posted by Spheric Harlot View Post
This is patently false.
No it's not. I am an expert.
     
Spheric Harlot
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Sep 22, 2011, 12:01 PM
 
Originally Posted by bstone View Post
No it's not. I am an expert.
In what?

With what expertise?

Do you build PA systems? Submarines?

What is your involvement with audio engineering?
     
bstone
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Sep 22, 2011, 12:02 PM
 
Originally Posted by Spheric Harlot View Post
In what?

With what expertise?

Do you build PA systems? Submarines?

What is your involvement with audio engineering?
I have a GED in Audio Spaghetti Engineering. About 30 years worth of experience.
     
Spheric Harlot
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Sep 22, 2011, 12:05 PM
 
Originally Posted by bstone View Post
I have a GED in Audio Spaghetti Engineering. About 30 years worth of experience.
I see:

Audio Spaghetti | Facebook

From the looks of it, it's probably worth getting your knowledge up to snuff WRT noise cancellation. It may improve the live experience.
     
bstone
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Sep 22, 2011, 12:06 PM
 
Originally Posted by Spheric Harlot View Post
I see:

Audio Spaghetti | Facebook

From the looks of it, it's probably worth getting your knowledge up to snuff WRT noise cancellation. It may improve the live experience.
They are imposters. There is a Small Claims Court lawsuit against them that will bankrupt them! Judge Judy!
     
Spheric Harlot
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Sep 22, 2011, 12:07 PM
 
I give you bonus points for finding a humorous way of admitting cluelessness.
     
bstone
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Sep 22, 2011, 12:09 PM
 
Originally Posted by Spheric Harlot View Post
I give you bonus points for finding a humorous way of admitting cluelessness.
Of course I don't know anything about this topic. We learned about the theory when I took physics in college. I guess it can be done, for a lot of money.
     
   
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