Engineering and the Environment, University of Southampton

Knowledge and understanding
Having successfully completed the module, you will be able to demonstrate knowledge and understanding of:

• Active control of plane waves in ducts.
• Strategies for active control including reflection and absorption.
• The use of quadratic optimisation in determining the performance of control systems.
• The principles of single-channel control systems for tonal and random signals.
• The use of the LMS algorithm in active control systems.
• Active control of freefield sound.
• Multichannel control of tones and random disturbances.
• Active control of enclosed soundfields.
• Active structural acoustic control using integrated actuators and sensors.
• Stability, performance and robustness of feedback systems.
• Active headsets.
• Active vibration isolation systems.
• Active control of waves in structures.

Cognitive (thinking) skills
Having successfully completed the module, you will be able to:

• Read, understand and interpret the literature relating to active sound and vibration control.
• Recognise and select appropriate techniques for the modelling and analysis of active control problems.

Practical, subject specific skills
Having successfully completed the module, you will be able to:

• Evaluate claims for the performance of active control systems.

Key transferable skills
Interpret manufacturers' catalogues.

• Integrate knowledge between the fields of acoustics, vibration, electronics and control.

The aims of this module are to:

• Give a broad understanding of the principles of active sound and vibration control.

• To introduce the physical principles involved in the active control of sound and vibration.
• To discuss the various control strategies which can be used, particularly adaptive feedforward and feedback.

Physics of Active Sound and Vibration Control

• Use of optimisation techniques in frequency and time domains.
• Controlled interference of wave fields (one-dimensional examples; sound propagation in a waveguide, flexural wave propagation in beams).
• Energy interchanges and power flows.
• Three-dimensional examples in free field sound propagation and two-dimensional flexural wave propagation.
• Treatment of enclosed sound fields at low and high modal densities.

Feedforward Control

• Reference signal techniques for "preview control" (e.g. sound propagation in 1﷓D waveguide.
• Digital realisation of transfer functions.
• Adaptive approaches and multichannel systems.
• Transfer function approaches and influence of feedback.

2 lectures a week.

Lectures include a combination of presentation, and the discussion of the properties of examples of practical loudspeakers and microphones handed round in class.

Two tutorials are arranged to review the material and revise for the examination.

Home study of the notes provided in the lectures. Students are encouraged to read supporting texts and papers and a booklist is provided.

Core text

Active Control of Sound,
1992, P A Nelson
S J Elliott, Academic Press
0125154259

Active Control of Vibration, 1995, C R Fuller
S J Elliott
P A Nelson, Academic Press
0122694406

Signal Processing for Active Control, 2001, S J Elliott, Academic Press
0122370856

Vibration Control of Active Structures, 1997, A Preumont, Kluwer
0792343921

Secondary text

Understanding active noise cancellation,2001, C H Hansen, E&FN Spon