Active noise control in ducts via side-branch resonators

Okamoto, Yasushi; Bodén, Hans; Åbom, Mats

doi:10.1121/1.410231

Cited by 12 publications

(6 citation statements)

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“…It implies z -m =e -jkl such that the Z-domain versions of Eqs. and (9) In Eq. 8 6and a pair of well matched sensors must be used to obtain w in and w out with u s =0 and u p persistently exciting.…”

Section: Controller Designmentioning

confidence: 99%

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Design and Implementation of an Active Absorber

Yuan

2007

Noise & Vibration Worldwide

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Active control may be introduced to resonators to improve noise control performance. Many active controllers depend on accurate transfer functions from speakers to error sensors to generate destructive interference. These transfer functions are sensitive to acoustical parameters in noise fields where error sensors are installed. An alternative strategy is to modify internal resonator impedance instead of destructive interference in noise fields. This approach focuses on the internal dynamics of a resonator and uses an equivalent primary source to model the external noise field. A controller is designed on the basis of the internal dynamics and is hence independent of external acoustical parameters. The controller improves absorption by minimising noise reflection inside the resonator. Such an active absorber is implemented and tested in experiments to achieve near perfect absorption performance in a wide frequency range. The closed-loop system is stable and reliable with respect to significant variations of acoustical parameters in the external field.

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Section: Controller Designmentioning

confidence: 99%

“…Hersh and Tso invented an active Helmholtz resonator with an extended frequency range [7,8]. Active side-branch resonators were applied to noise control in ducts by Okamoto et al [9] and Utsumi [10]. Those methods generate destructive interference in noise fields.…”

Section: Introductionmentioning

confidence: 99%

Design and Implementation of an Active Absorber

Yuan

2007

Noise & Vibration Worldwide

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“…Plane waves are easier to control and much of the duct research specifically mentions that the experimental design was set to focus on plane waves only. Among others, this was the approach of Eghtesadi et al (1986), Egana et al (2003), La Fontaine and Shephard (1991), Okamoto et al (1994), Zimmer et al (2003), and Wu et al (1996). Higher order modes are more difficult to control but not impossible.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Eriksson and Allie (1988) used the Nelson Digisonix dX-30 system in an article that was more of an advertisement for the product. Okamoto et al (1994) used the Activox controller. Slagley and Guffey (2006) and the current study used the EZ-ANC II controller (Causal Systems, Inc., Adelaide, Australia), since it is the only commercial ANC system currently available.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Zhou and Shi (1991) used an L-formed duct instead of the dipole to reduce feedback and increase performance of ANC in ducts. Okamoto et al (1994) altered the housing of the control speaker to make it a resonator and thereby reduced the needed volume velocity (amount of available sound power) of the control speaker. The builders of the EZ-ANC II system discussed the physical issues that make a problem amenable to ANC solution, as well as offering basic guidance (Snyder and Hansen, 1989;Snyder, 2001).…”

Section: Literature Reviewmentioning

confidence: 99%

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Effects of diameter and cross-sectional partitioning on active noise control in round ducts

Slagley¹

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EFFECTS OF DIAMETER AND CROSS-SECTIONAL PARTITIONING ON ACTIVE NOISE CONTROL IN ROUND DUCTS by Jeremy M. Slagley Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct. The lowest frequency for higher order modes will increase as duct diameter decreases. Therefore, the range of frequencies where plane waves dominate will be greater and effective control using ANC better as duct diameter decreases. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. To test those suppositions, a commercially-available ANC system was used to reduce random noise in round ducts having five different diameters. Results showed that insertion loss (IL) ranged from 5 to 30 dB in frequencies ranging from 40-1000 Hz, and varied inversely with size as expected. The same tests were conducted on a rectangular duct with one cross-sectional dimension fixed and one varied at seven different sizes. Results showed similar IL from 5 to 30 dB that varied inversely with size. If smaller diameters have broader frequency ranges that can be controlled with ANC, perhaps one could extend the frequency range for a large cross-section by partitioning it into smaller cross-sections. This hypothesis was tested by two methods of cross-sectional partitioning. Partitioning was achieved in one design by inserting a smaller duct inside a large duct. In a second design, a cross-shaped partition was inserted inside the large duct. ANC IL results were 1.7 to 2 dB better for the large duct partitioned by a smaller inner duct than the large duct alone (p=0.0146 for low frequency and p=0.0333 for high frequency). ANC insertion loss was 5.8 dB better for the large duct partitioned by a cross-shaped splitter at high frequencies than the large duct alone (p=0.0003). However, the cross-shaped partition system was 5.6 dB less effective at low frequencies than the large duct ANC IL alone (p<0.0001). The designs were evaluated to determine the minimal system requirements to achieve a substantial increase in IL inside a large diameter duct iii DEDICATION The author wishes to dedicate this work to his father, Charles A. Slagley, Jr., who passed away after a short struggle with cancer on 16 Jan 2005. He was an educator and inspiration to many, selected as Illinois Secondary School Principal of the Year for 2003. This work is also dedicated to the author's fifth child, Rosemary Claire, who was born in August, 2004. She reminded us all of the joys of life in this valley of tears. Her "Buka" got to hold her before he died. iv ACKNOWLEDGMENTS The author wishes to acknowledge some of the many people and organizations who contributed to or facilitated the work herein. Firstly, I acknowledge my utter dependence on Almighty God. I am al...

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Absorber mit aktiven Komponenten

Fuchs¹

2010

Schallabsorber Und Schalldämpfer

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Active noise control in ducts via side-branch resonators

Cited by 12 publications

References 0 publications

Design and Implementation of an Active Absorber

Design and Implementation of an Active Absorber

Effects of diameter and cross-sectional partitioning on active noise control in round ducts

Absorber mit aktiven Komponenten

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