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1.1  How to use this FAQ

You can always find the latest version of this document here:

If you have general questions about active noise control, please post them in this newsgroup: news:alt.sci.physics.acoustics. To contribute to the FAQ or provide comments, praise, or criticism directly to the FAQ maintainer, send email to

To cite this FAQ as a reference: There is no universally accepted format for citing an Internet resource as a reference, but the following citation would be suitable for many publications:

Ruckman, C.E., "Frequently Asked Questions: Active Noise Control," Internet FAQ document, available on the Worldwide Web at, February 2007.

1.2  What's new in the Active Control FAQ

In 1994, the Acoustical Society of America presented the author, Dr. Chris Ruckman, with its 1994 Science Writing Award for this FAQ. The award recognizes "distinguished writing (or producing) that improves public understanding and appreciation of acoustics." The ASA, which gives two such awards each year, had never before honored a work published only on the Internet.

Date:           Topic added or changed:

2007-02-03   Moved to; updated and reformatted.

2001-02-27   Info on patents database; MathTools link.

2000-08-06   Updated format; updated some company info.

1999-07-31   Removed most links and other "perishable" information.

1998-02-14   Web site moved to

1997-11-13   updated contact info and some web sites

1996-11-10   FAQ broken into 3 files

1996-06-23   translated to HTML

1995-12-04   rearranged sections; archive-name changed back to original

1995-11-27   archive-name changed

1995-02-24   expanded intro, revised format, added basics (1.5)

1994-06-14   initial release

1.3  Contributors

The following people contributed to the discussions upon which this FAQ is based:

Ralph T. Muehleisen, Chris Lawrenson, Stephen Lajoie, Susan Mercy, Rolf Diehl, Jeffrey Stuart Vipperman, Marcus Bronzel, Johan L. Nielsen, Colin Hansen, Michel Schonewille, Soeren Laugesen, Todd Toles, John Gilliver, Lee Leggore, Chris Fuller, Birger Bech Jessen, Dr. Dexter Smith, and many others. 

1.4  Copyright information and disclaimer

Copyright (c) 1994-2007 by Christopher E. Ruckman. All Rights Reserved.

All rights are reserved. Christopher E. Ruckman ("Author") hereby grants permission to use, copy and distribute this document for any NON-PROFIT purpose, provided that the article is used in its complete, UNMODIFIED form including both the above Copyright notice and this permission notice. Reproducing this article by any means, including (but not limited to) printing, copying existing prints, or publishing by electronic or other means, implies full agreement to the above non-profit-use clause. Exceptions to the above, such as including the article in a compendium to be sold for profit, are permitted only by EXPLICIT PRIOR WRITTEN CONSENT of Christopher E. Ruckman.

Disclaimer: This document represents the personal opinions of the Author, and does not necessarily represent the opinion of the US Government or the Author's employer, nor anyone other than the Author. Any mentions of commercial products, company names, or universities are solely for information purposes and do not imply any endorsement by the Author or any other entity. The Author provides this article "as is." The Author disclaims any express or implied warranties including, but not limited to, any implied warranties of commercial value, accuracy, or fitness for any particular purpose. If you use the information in this document in any way, you do so entirely at your own risk.

Copyright (c) 1994-2007 by Christopher E. Ruckman. All Rights Reserved.



This site was last updated 02/04/07