Active control of low frequency ‘buzz-saw’ tones radiated from an aircraft engine on take off
Active control of low frequency ‘buzz-saw’ tones radiated from an aircraft engine on take off
This thesis details a feasibility study into the use of active control for the attentuation of the low frequency components of the ‘buzz-saw’ sound field radiated from an aircraft engine on take off. Passive liner sections are currently used to attenuate the sound field, however, they have insufficient thickness to attenuate sufficiently the very low frequency components of the sound field. An active control system positioned after the liner section could be used to further attenuate the sound field.
This thesis shows that due to the simple modal structure of the buzz-saw noise, effective control of the sound field can be achieved by minimising the sum of the square pressures at a single ring of error sensors using a single ring of control actuators. In the absence of noise and extraneous modes, the level of control performance is fundamentally limited by the level of the evanescent modes at the error sensor array. An analytic model is developed which predicts the sound power reduction. Reflections are shown to be important in the control mechanism with standing wave regions identified between the secondary source array and the exhaust termination and between the inlet termination and the error sensor array.
The thesis concludes with the results from an experimental rig. A real-time FXLMS algorithm is used to control a synthesised low order spinning mode by minimising the sum of the squared pressures measured at a single ring of 7 sensors using a simple ring of 7 control actuators. The relationship between sound pressure reduction at the error sensors and the transmitted sound power is investigated. Sound power reductions of up to 14.5dB are achieved. The control mechanism is identified from computer simulation.
University of Southampton
Wilkinson, Matthew Jon
ac44d10e-59d2-43b5-b146-b953325b998f
2004
Wilkinson, Matthew Jon
ac44d10e-59d2-43b5-b146-b953325b998f
Wilkinson, Matthew Jon
(2004)
Active control of low frequency ‘buzz-saw’ tones radiated from an aircraft engine on take off.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis details a feasibility study into the use of active control for the attentuation of the low frequency components of the ‘buzz-saw’ sound field radiated from an aircraft engine on take off. Passive liner sections are currently used to attenuate the sound field, however, they have insufficient thickness to attenuate sufficiently the very low frequency components of the sound field. An active control system positioned after the liner section could be used to further attenuate the sound field.
This thesis shows that due to the simple modal structure of the buzz-saw noise, effective control of the sound field can be achieved by minimising the sum of the square pressures at a single ring of error sensors using a single ring of control actuators. In the absence of noise and extraneous modes, the level of control performance is fundamentally limited by the level of the evanescent modes at the error sensor array. An analytic model is developed which predicts the sound power reduction. Reflections are shown to be important in the control mechanism with standing wave regions identified between the secondary source array and the exhaust termination and between the inlet termination and the error sensor array.
The thesis concludes with the results from an experimental rig. A real-time FXLMS algorithm is used to control a synthesised low order spinning mode by minimising the sum of the squared pressures measured at a single ring of 7 sensors using a simple ring of 7 control actuators. The relationship between sound pressure reduction at the error sensors and the transmitted sound power is investigated. Sound power reductions of up to 14.5dB are achieved. The control mechanism is identified from computer simulation.
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Published date: 2004
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Local EPrints ID: 465454
URI: http://eprints.soton.ac.uk/id/eprint/465454
PURE UUID: 8b09ca86-80c6-40b3-a5f6-e210c874bc93
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Date deposited: 05 Jul 2022 01:07
Last modified: 16 Mar 2024 20:11
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Author:
Matthew Jon Wilkinson
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