IOS Press Book reviewdownloads.hindawi.com/journals/sv/2002/264984.pdf · Shock and Vibration 9 (2002) 151 151 IOS Press Book review Understanding Active Noise Cancellation, Colin

Shock and Vibration 9 (2002) 151 151IOS Press

Book review

Understanding Active Noise Cancellation, ColinH. Hansen

Understanding Active Noise Cancellation is a muchneeded book in the field of acoustics and active con-trol and Colin Hansen does a thorough job of coveringall the major aspects. In order for active noise controlto become more practical than is has over the last 15years it is essential that there is a more in depth under-standing throughout the noise control community. Thisbook highlights one of the major reasons why this hasnot happened, that is that active noise control requiresunderstanding of several complex fields, the subtletiesof each play an important role in the final performanceof an active system. A successful active noise controlengineer has an understanding of acoustics, vibration,signal processing and adaptive filters, DSP hardwareand programming, transducer design and power elec-tronics.

Like many textbooks this one is based on a seriesof lectures and at times this becomes apparent as thebreadth of material covered assumes that a large amountfurther reading will be undertaken. The introductionis particularly guilty of this as the author tries to in-troduce and explain the majority of active control sys-tems, leaving the reader somewhat disorientated by therapid switches between details and broad statements.Thankfully the remainder of the book clarifies the top-ics introduced here and is well structured.

Foundations of active control are discussed in chap-ter two, which couples well with the third chapter thatdiscusses adaptive algorithms. A very clear descriptionof the filtered-x-LMS algorithm is given, however thediscussion of neural networks as adaptive filters in ac-tive control may be slightly esoteric for a book whichis meant to be an introduction to the fundamentals ofactive noise control.

Secondary sound sources are the subject of the fourthchapter and the practical considerations such as tem-perature range, durability, stability of response are well

treated. The discussion of an active noise control sys-tem for industrial chimneys spewing hot gas gives foodfor thought for those of us who spend the majority of ourtime working in controlled laboratory environments. Inkeeping with the scope of the book little technical de-tail of various transducer mechanisms is given as mostpractical control system use standard loudspeakers orinertial shakers. As is the case throughout the booka good number of references for further reading areprovided.

Wave synthesis, modal and standard vibration andpressure sensors, energy density and intensity sensors,potential energy, sum of squared pressures are all dis-cussed with regard to reference and error sensing. Aswith most of the book the mathematics is light but lu-cid descriptions of the physics are given. The finalchapter is a review of noise control applications, casesin point are the active headsets found on commercialairlines and transmission loss through simple panels.The final section of the book is given over to discussingnoise control problems that will always be impractical,such as global reduction transient and broadband, noiseoutdoors, global reduction of high frequencies in largespaces etc. This section is invaluable to those who havehad to spend their entire time at a party explaining whynothing can be done about noisy neighbors.

This book fulfils its purpose well as a review of thecurrent position of active noise control in both practicaland research fields. Although not in depth enough togain a complete understanding of the problems facingthe active control system designer it is a good introduc-tory text that points the reader in the correct directions.

M.R.F. KidnerVibrations and Acoustics LaboratoryVirginia Polytechnic Institute and State UniversityBlacksburg VA 24060USAE-mail: [email protected]

ISSN 1070-9622/02/$8.00 2002 – IOS Press. All rights reserved

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IOS Press Book reviewdownloads.hindawi.com/journals/sv/2002/264984.pdf · Shock and Vibration 9 (2002) 151 151 IOS Press Book review Understanding Active Noise Cancellation, Colin