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Mid-frequency local active control of road noise

Mid-frequency local active control of road noise
Mid-frequency local active control of road noise
Interior road noise in vehicle cabins is mainly random and broadband, and can potentially be controlled using either passive or active methods. Previous active noise control systems have typically used secondary loudspeakers that are remote from a listener’s ears, however, and this has limited their useful frequency range to below about 300 Hz. An active headrest system, with closely-spaced secondary loudspeakers and error sensors, may be a practical method of increasing this frequency range, using local active sound control. This thesis presents developments of the local active control strategy, with the aim of improving the attenuation performance and the convergence stability of active headrest systems in vehicles.

An active headrest system is first investigated via simulation, to understand the fundamental characteristics of local active control in enclosures. The application of a headtracking device to the active headrest system is then investigated initially to allow the active headrest system to use an appropriate plant response in order to maintain stability. The remote microphone technique is then investigated, which uses the output from fixed monitoring microphones to estimate the signals at virtual error microphones at the listener’s ears, via an observation filter. It is shown that the geometry of the monitoring microphone array should be chosen considering both the spatial correlation of the primary field and the condition number of the inversion associated with the design of the observation filter.

The head-tracking device and the remote microphone technique have been integrated in an active headrest system. A real-time implementation is presented of the nearfield estimation and integrated active headrest system for controlling either tonal or broadband sounds. In particular, the effects of using the head-tracking device during the control have been investigated with a human listener. Measurements of the road noise and acoustic response in a large SUV have also been conducted, and these are used to predict the performance of an active headrest system under various practical conditions, with promising results.
University of Southampton
Jung, Woomin
d8734210-d7b3-48dc-ace0-3724cd864f37
Jung, Woomin
d8734210-d7b3-48dc-ace0-3724cd864f37
Cheer, Jordan
8e452f50-4c7d-4d4e-913a-34015e99b9dc

Jung, Woomin (2018) Mid-frequency local active control of road noise. University of Southampton, Doctoral Thesis, 298pp.

Record type: Thesis (Doctoral)

Abstract

Interior road noise in vehicle cabins is mainly random and broadband, and can potentially be controlled using either passive or active methods. Previous active noise control systems have typically used secondary loudspeakers that are remote from a listener’s ears, however, and this has limited their useful frequency range to below about 300 Hz. An active headrest system, with closely-spaced secondary loudspeakers and error sensors, may be a practical method of increasing this frequency range, using local active sound control. This thesis presents developments of the local active control strategy, with the aim of improving the attenuation performance and the convergence stability of active headrest systems in vehicles.

An active headrest system is first investigated via simulation, to understand the fundamental characteristics of local active control in enclosures. The application of a headtracking device to the active headrest system is then investigated initially to allow the active headrest system to use an appropriate plant response in order to maintain stability. The remote microphone technique is then investigated, which uses the output from fixed monitoring microphones to estimate the signals at virtual error microphones at the listener’s ears, via an observation filter. It is shown that the geometry of the monitoring microphone array should be chosen considering both the spatial correlation of the primary field and the condition number of the inversion associated with the design of the observation filter.

The head-tracking device and the remote microphone technique have been integrated in an active headrest system. A real-time implementation is presented of the nearfield estimation and integrated active headrest system for controlling either tonal or broadband sounds. In particular, the effects of using the head-tracking device during the control have been investigated with a human listener. Measurements of the road noise and acoustic response in a large SUV have also been conducted, and these are used to predict the performance of an active headrest system under various practical conditions, with promising results.

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Published date: June 2018

Identifiers

Local EPrints ID: 427150
URI: http://eprints.soton.ac.uk/id/eprint/427150
PURE UUID: c55c6212-da85-4165-9fed-2a489b5c2357
ORCID for Jordan Cheer: ORCID iD orcid.org/0000-0002-0552-5506

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Date deposited: 03 Jan 2019 17:30
Last modified: 14 Mar 2019 01:37

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Contributors

Author: Woomin Jung
Thesis advisor: Jordan Cheer ORCID iD

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