JMC method applied to active control of sound

Theoretical extensions and new source configurations: Dissertation

Seppo Uosukainen

Research output: ThesisDissertationCollection of Articles

Abstract

The active control of sound can be used to control the acoustics of interior spaces, to reduce the sound radiation of machines and equipment, to decrease and even to refine noise in a more comfortable form in, e.g., ducts and vehicles.The JMC method, developed by Jessel, Mangiante and Canévet, is a systematic tool in the active control of sound.It is applied mostly by using scalar weighting, in which all the first-order field quantities and primary source strengths are weighted similarly.In this thesis, a modified JMC method is developed, in which the primary sources remain unchanged in all cases, the situation being more similar to a practical one.On the basis of the modified JMC method, the vector and dyadic weightings are defined, the former weighting the sound pressure and particle velocity independently, and the latter also changing the direction of the particle velocity.These new weightings increase the possibilities in field reshaping.In the JMC method, three types of secondary sources are needed: monopoles, dipoles and quadripoles.It is found that in multi-source configurations, the last ones are automatically generated by the dependence of the dipole distribution on the lateral coordinates.Four three-unit approximations of the JMC element (i.e., detector-actuator combination according to the JMC method) are developed, in which one of either the primary field quantities or the secondary source quantities is approximated by the help of a field impedance function.For waveguides (e.g., ducts), ideal unidirectional three-element and two-element JMC source configurations and their approximations are discovered.The inter-channel delay in the control structure of the two-element actuators may be optimized downstream or upstream, or omitted altogether.Especially the last case turns out to be advantageous in the practical implementation of digital control systems.The adaptive JMC structures for the new ideal two-element solutions are presented.The results of this thesis enlarge the possibilities in the active control of sound and facilitate more useful applications to be realized in ducts and three-dimensional spaces.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Karjalainen, Matti, Supervisor, External person
Award date28 May 1999
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5377-2
Electronic ISBNs951-38-5378-0
Publication statusPublished - 1999
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

active control
acoustics
configurations
ducts
theses
actuators
dipoles
dyadics
sound pressure
approximation
monopoles
upstream
vehicles
impedance
scalars
waveguides
detectors
radiation

Keywords

  • ducts
  • JMC method
  • JMC element
  • active noise control
  • waveguide
  • unidirectional actuators

Cite this

Uosukainen, Seppo. / JMC method applied to active control of sound : Theoretical extensions and new source configurations: Dissertation. Espoo : VTT Technical Research Centre of Finland, 1999. 70 p.
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abstract = "The active control of sound can be used to control the acoustics of interior spaces, to reduce the sound radiation of machines and equipment, to decrease and even to refine noise in a more comfortable form in, e.g., ducts and vehicles.The JMC method, developed by Jessel, Mangiante and Can{\'e}vet, is a systematic tool in the active control of sound.It is applied mostly by using scalar weighting, in which all the first-order field quantities and primary source strengths are weighted similarly.In this thesis, a modified JMC method is developed, in which the primary sources remain unchanged in all cases, the situation being more similar to a practical one.On the basis of the modified JMC method, the vector and dyadic weightings are defined, the former weighting the sound pressure and particle velocity independently, and the latter also changing the direction of the particle velocity.These new weightings increase the possibilities in field reshaping.In the JMC method, three types of secondary sources are needed: monopoles, dipoles and quadripoles.It is found that in multi-source configurations, the last ones are automatically generated by the dependence of the dipole distribution on the lateral coordinates.Four three-unit approximations of the JMC element (i.e., detector-actuator combination according to the JMC method) are developed, in which one of either the primary field quantities or the secondary source quantities is approximated by the help of a field impedance function.For waveguides (e.g., ducts), ideal unidirectional three-element and two-element JMC source configurations and their approximations are discovered.The inter-channel delay in the control structure of the two-element actuators may be optimized downstream or upstream, or omitted altogether.Especially the last case turns out to be advantageous in the practical implementation of digital control systems.The adaptive JMC structures for the new ideal two-element solutions are presented.The results of this thesis enlarge the possibilities in the active control of sound and facilitate more useful applications to be realized in ducts and three-dimensional spaces.",
keywords = "ducts, JMC method, JMC element, active noise control, waveguide, unidirectional actuators",
author = "Seppo Uosukainen",
note = "Project code: R9SU00259",
year = "1999",
language = "English",
isbn = "951-38-5377-2",
series = "VTT Publications",
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JMC method applied to active control of sound : Theoretical extensions and new source configurations: Dissertation. / Uosukainen, Seppo.

Espoo : VTT Technical Research Centre of Finland, 1999. 70 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - JMC method applied to active control of sound

T2 - Theoretical extensions and new source configurations: Dissertation

AU - Uosukainen, Seppo

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N2 - The active control of sound can be used to control the acoustics of interior spaces, to reduce the sound radiation of machines and equipment, to decrease and even to refine noise in a more comfortable form in, e.g., ducts and vehicles.The JMC method, developed by Jessel, Mangiante and Canévet, is a systematic tool in the active control of sound.It is applied mostly by using scalar weighting, in which all the first-order field quantities and primary source strengths are weighted similarly.In this thesis, a modified JMC method is developed, in which the primary sources remain unchanged in all cases, the situation being more similar to a practical one.On the basis of the modified JMC method, the vector and dyadic weightings are defined, the former weighting the sound pressure and particle velocity independently, and the latter also changing the direction of the particle velocity.These new weightings increase the possibilities in field reshaping.In the JMC method, three types of secondary sources are needed: monopoles, dipoles and quadripoles.It is found that in multi-source configurations, the last ones are automatically generated by the dependence of the dipole distribution on the lateral coordinates.Four three-unit approximations of the JMC element (i.e., detector-actuator combination according to the JMC method) are developed, in which one of either the primary field quantities or the secondary source quantities is approximated by the help of a field impedance function.For waveguides (e.g., ducts), ideal unidirectional three-element and two-element JMC source configurations and their approximations are discovered.The inter-channel delay in the control structure of the two-element actuators may be optimized downstream or upstream, or omitted altogether.Especially the last case turns out to be advantageous in the practical implementation of digital control systems.The adaptive JMC structures for the new ideal two-element solutions are presented.The results of this thesis enlarge the possibilities in the active control of sound and facilitate more useful applications to be realized in ducts and three-dimensional spaces.

AB - The active control of sound can be used to control the acoustics of interior spaces, to reduce the sound radiation of machines and equipment, to decrease and even to refine noise in a more comfortable form in, e.g., ducts and vehicles.The JMC method, developed by Jessel, Mangiante and Canévet, is a systematic tool in the active control of sound.It is applied mostly by using scalar weighting, in which all the first-order field quantities and primary source strengths are weighted similarly.In this thesis, a modified JMC method is developed, in which the primary sources remain unchanged in all cases, the situation being more similar to a practical one.On the basis of the modified JMC method, the vector and dyadic weightings are defined, the former weighting the sound pressure and particle velocity independently, and the latter also changing the direction of the particle velocity.These new weightings increase the possibilities in field reshaping.In the JMC method, three types of secondary sources are needed: monopoles, dipoles and quadripoles.It is found that in multi-source configurations, the last ones are automatically generated by the dependence of the dipole distribution on the lateral coordinates.Four three-unit approximations of the JMC element (i.e., detector-actuator combination according to the JMC method) are developed, in which one of either the primary field quantities or the secondary source quantities is approximated by the help of a field impedance function.For waveguides (e.g., ducts), ideal unidirectional three-element and two-element JMC source configurations and their approximations are discovered.The inter-channel delay in the control structure of the two-element actuators may be optimized downstream or upstream, or omitted altogether.Especially the last case turns out to be advantageous in the practical implementation of digital control systems.The adaptive JMC structures for the new ideal two-element solutions are presented.The results of this thesis enlarge the possibilities in the active control of sound and facilitate more useful applications to be realized in ducts and three-dimensional spaces.

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KW - JMC element

KW - active noise control

KW - waveguide

KW - unidirectional actuators

M3 - Dissertation

SN - 951-38-5377-2

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Uosukainen S. JMC method applied to active control of sound: Theoretical extensions and new source configurations: Dissertation. Espoo: VTT Technical Research Centre of Finland, 1999. 70 p.