Active Noise Cancelling and ultra low frequent singularities!

Hi,
In active noise cancelling systems for head-phones there seems to be a focus on ultra low frequent singularities (< a few Hz). Can anyone
tell me how these are related to some physical attributes of the plant (speaker,microphone, amp and acoustical path in between transducers)?
Cheers Tom
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This question would be better directed to the alt.sci.physics.acoustics group.
It is also unclear what you are trying to ask. Below 20 Hz is generally considered out of the range of normal hearing. Are you sure they are trying to cancel that?
This answers lots of questions: http://www.chrisruckman.com/ancfaq.htm
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Daniel Helmick wrote:

I can only guess, but in any kind of signal processing if you're interested in phenomena at X Hz, you have to pay attention to X/10 Hz and 10*X Hz. So a singularity at just a few Hz could conceivably screw up the math for processing at 20Hz.
But this is just a (somewhat) educated guess -- I agree that the OP should seek out a group with closer knowledge.
--

Tim Wescott
Wescott Design Services
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I agree with you Tim - I just wonder what causes these ultra low frequent singularities!
Thanks

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Thanks for the direction!

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