h a l f b a k e r yContrary to popular belief
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Self explanatory. Uses the same speakers as the in-car stereo system. Microphones mounted on the interior and exterior allow cancelation of noise from the exterior of the vehicle.
The basic (passive) mode simply allows you to enjoy peaceful quiet. As the noise canelation technology is built into
the stereo, it does not impact your radio listening pleasure (the signal is accounted for). Additionally, normal voice frequencies at normal amplitudes are not effected.
The active mode (costs extra) uses externally mounted speakers to cancel noises outside the vehicle. Now that kid with the 12" bass speaker can't impress his friends.
(HB veterans: Note the conspicuous absence of genetic engineering, phosphorescence, pizza and nanotechnology!)
Acoustical Society of America
http://www.acoustic...s/136th/couche2.htm
Like this, you mean? [hippo, Aug 29 2001, last modified Oct 21 2004]
The Active Noise Control FAQ
http://www.faqs.org...-noise-control-faq/
[hippo, Aug 29 2001, last modified Oct 21 2004]
Honda Accord noise control system
http://ne.nikkeibp....06/0626honda_v.html
Baked, but possibly after this was written! Jutta pointed me back to this one from my Baby volume control [wagster, Oct 04 2004, last modified Oct 21 2004]
[link]
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phoenix: //Note the conspicuous absence of genetic engineering, phosphorescence...// |
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Hmmm. Good idea, lacks custard. |
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Damn! I knew I was forgetting something. |
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I thought noise cancellation only worked at the source or at the ear. Otherwise whether the sounds are in phase depends on where you're sitting. |
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[UnaBubba] Sorry, no. In fact you could say this is anti-explosion. |
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Neither does it run off lightning, urine or rain. It won't effect your lawn, home interior or lighting conditions. It won't give you extra-human powers, change your country's form of government or modify anyone's bathroom behavior. |
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Now that I think about it, this idea is no fun at all. |
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Unlikely to work, but not boring. By the time the microphones have detected the sound and inverted it, it's already gone, for the outside ones. I'd love one of the inside ones, though... |
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Geeks have been working on this sort of thing for quite some time. It is already known that by placing a sufficient number of microphones and speakers in various places in and around the volume of interest, it is possible to make silent an arbitrarily large number of points within that volume. It requires sending each speaker a special mix of all of the microphones' signals. Each speaker requires a different mix whose formula is a function of the placement of each microphone, each speaker, and the locations of the points to be made silent. |
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One problem is the phrase "sufficient number". For exactly one silent point, 3 speakers and 3 microphones would be needed. The number of microphones and speakers multiplies for each additional point to be made silent. |
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Another problem is that when I say "point" I mean the mathematical definition of the word. The point has zero width, zero length, and zero depth. Also each point is static relative to the boundaries of the volume. However, the driver's and passesngers' ears are not stationary. They move frequently within the volume of the auto's cabin. To cope with this fact, you would need to make silent the many, many points where people's ears *might* be at a given time. |
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Finally, although the number of speakers and microphones grows linearly with the number of points to be controlled, the mathematical complexity of computing the correct signals to feed all of the speakers grows as N^2. I *dare* you to genetically engineer a phosphorescent nano-pizza with enough artificial intelligence to compute the signals for all the speakers you'd need to keep just one person comfortable! |
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<sound voice="Peter Falk" character="Columbo">
Oh yes, just one more thing.
</sound> |
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A great deal of the road and wind noise is voice band (1-4KHz) so if you intentionally avoid cancelling these frequencies, you have not accomplished much of your initial task. It could still work (inside the car) to cancel the thumps coming from the car next to yours, though. |
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great idea I am working on something similar to this and have had very little help, can you help me or do you have a prototype ready for testing because I can help to test it!!!!!!!!!! |
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It found this is a good idea. If can do it, we can have good driving. Anyone have trying circuit on the car. |
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Beep. Beeeeep. BEEEEEEEEEEEEEEEEEEEP! *crashhhzmmgghargh* |
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"You idiot! Didn't you hear me honking my horn?" |
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