Skip to main content
padlock icon - secure page this page is secure

Adaptive Control of Broadband Sound in Ducts Using a Pair of Loudspeakers

Buy Article:

$30.00 + tax (Refund Policy)

Practical active systems for the cancellation of broadband noise in ducts have, to date, almost exclusively used a single secondary loudspeaker. With a single loudspeaker, a large change of impedance in the duct can be realised so that the incident waves are reflected back in the upstream direction.

In order to absorb the incident sound wave, rather than just reflect it, a secondary source pair has been used in this work based on a proposal by Swinbanks. The source pair is capable of generating a uni-directional downstream wave, and the effect of standing waves and extra resonances in the upstream direction can thus be avoided. The controller has been implemented on a digital signal processing device and has been made adaptive using the LMS algorithm. The control of broadband noise over a frequency range of 2–3 octaves has been achieved with attenuation levels of 20–40 dB and the adaptive control system has been shown to be robust.

The performance of the Swinbanks' source has been compared to that of a single loudspeaker and that of a “maximally efficient” source that can be realised by two loudspeakers. It has been found that the Swinbanks' source is the preferable solution, giving good reductions in the downstream and upstream directions, stabilizing the adaptive algorithm by reducing feedback effects, and placing least demand on the loudspeakers.

Zusammenfassung

Systeme zur aktiven Abschwächung von breitbandigem Schall in Kanälen setzen bisher fast ausschließlich einen einzelnen Lautsprecher zur Kompensation ein. Dieser realisiert im Kanal einen Impedanzsprung und reflektiert damit die einfallenden Schallwellen. Um den Schall absorbieren zu können, wurde in dieser Arbeit ein System mit zwei Lautsprechern realisiert, das auf einem Vorschlag von Swinbanks (1973) basiert. Das Lautsprecherpaar ist in der Lage, Schallwellen einseitig gerichtet abzustrahlen und vermeidet somit stehende Wellen und damit verbundene Resonanzeffekte zwischen Sekundärquelle und rückwärtigem Kanalabschluß. Die Implementierung erfolgte adaptiv unter Verwendung des LMS-Algorithmus. Über einen Frequenzbereich von 2–3 Oktaven wurden breibandige Schallminderungen von 20–40 dB erreicht.

Die Swinbanks-Anordnung wurde experimentell mit einem einzelnen Lautsprecher und mit einer “maximal effizienten” Anordnung zweier Lautsprecher verglichen. Sie erwies sich dabei als die günstigste Lösung, da sie in der Lage ist, eine hohe Schallminderung in beide Kanalrichtungen zu bewirken, durch die Reduzierung der Rückkopplungseffekte den Algorithmus zu stabilisieren und zusätzlich die Lautsprecher zu entlasten.

Sommaire

Les systèmes pratiques d'attenuation active de bruit à large bande dans les guides ont presque exclusivement utilisä un haut-parleur secondaire unique. Un tel haut-parleur unique peut provoquer dans le guide une modification importante de l'impédance, de sorte que les ondes incidentes sont réfléchies vers leur source.

Pour absorber l'onde acoustique incidente, au lieu de simplement la réfléchir, nous avons dans ce travail utilisé une paire de sources secondaires, comme l'avait proposé Swinbanks en 1973. La paire de sources est capable de produire une onde unidirectionnelle dans la direction aval, ce qui évite la production d'ondes stationnaires et de résonances supplémentaires en amont. Le contrêle est assure par un dispositif de traitement du signal, que l'on a rendu adaptatif en utilisant un algorithme LMS. Il permet d'obtenir une atténuation de 20 à 40 dB sur une étendue de deux à trois octaves d'un bruit è large bande; le dispositif s'est de plus révélé robuste.

On a comparé les performances d'une source de Swinbanks à celles d'un haut-parleur unique et à celle d'une source à «efficacité maximale» constitutée de deux haut-parleurs. On a trouvé que la source de Swinbanks fournit la meilleure solution, car elle produit une bonne attenuation, elle stabilise l'algorithme adaptatif en réduisant les effets de contre-réaction, et elle impose moins de contrainte sur les haut-parleurs.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
No Metrics

Document Type: Research Article

Publication date: September 1, 1995

More about this publication?
  • Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
  • Editorial Board
  • Information for Authors
  • Submit a Paper
  • Subscribe to this Title
  • Information for Advertisers
  • Online User License
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more