Engineering and the Environment, University of Southampton

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

• Show familiarity with noise control requirements, including main EU legislation applying to products.
• Use common units of noise measurement, including mean-square pressure, decibel units and reference values, frequency spectra and the A-weighted level.
• Characterise noise sources according to their physical behaviour, acoustic efficiency, frequency spectrum and dependence on operational speed.
• Be familiar with standard methods for the measurement of sound power, their advantages and limitations.
• Distinguish the main principles of noise control and understand the typical frequency dependence of noise control systems.
• Use simple models for the sound radiation of common sources including plates.
• Use appropriate formulae for the sound transmission through partitions.
• Understand the relation between surface impedance and absorption coefficient and the influence of the main physical parameters.
• Determine the effects of vibration isolation using a mobility model.
• Explain the influence of damping and the main means of achieving it.

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

• Evaluate the performance of appropriate noise control techniques for the solution of practical noise problems.

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

• Apply the noise control techniques considered in an integrated way to a practical design case.

Key transferable skills

Write a report suitable for a client or manager.

The aims of this module are to:

• Introduce the requirements, principles and methods of noise control.
• Provide basic knowledge and understanding of noise control necessary for professional practice as a noise control engineer.
• Encourage the application of this knowledge to practical problems.

• To describe the basis of how to set targets for noise control.
• To explain how to characterise, categorise, quantify and identify noise sources.
• To introduce the main principles of noise control available to the engineer and to place them in a logical framework.
• To derive the performance of noise control systems using simple mathematical models.
• To describe physical characteristics of noise control systems and their application in practice.

Noise control requirements

• The need for noise control.
• EC directives on machinery noise and outdoor equipment.
• Specification of noise control targets.

Units of noise measurement

• Sound pressure, intensity and power levels, reference values.
• Frequency analysis. dB(A) and other frequency weighted units.
• Combining sound pressures (incoherent and coherent).

Characterization of noise sources

• Physical nature of noise sources, idealizations.
• Mechano-acoustic efficiency.
• Frequency spectrum.
• Parametric dependencies including operational speed.

Noise source quantification

• Limitations of sound power as a source strength quantity. Effect of reflecting surfaces.
• Free field (anechoic) test method.
• Reverberant field method, including Sabine formula.
• Sound intensity methods.
• Use of surface vibration.

Principles of passive noise and vibration control

• Effect of multiple sources and multiple paths. Noise path models.
• Control at source. Airborne transmission. Structure-borne transmission.

Sound radiation from vibrating structures

• Definition of radiation ratio.
• Results for monopole and dipole sources.
• Radiation from bending waves in plates.
• Corner modes, edge modes, coincidence.
• Means of reducing radiation ratio.

Transmission of airborne sound through partitions

• Transmission loss of a single partition, mathematical derivation for normal incidence.
• Coincidence and the transmission loss for particular angles of incidence and for a diffuse field (qualitative).
• Double partitions (qualitative).
• Measurement methods for sound reduction index.
• Machinery enclosures using Sabine formula.

Sound absorbent materials and applications

• Qualitative treatment of dissipation mechanisms.
• Surface impedance and its relation to absorption coefficient.
• Practical forms of sound absorbers including resonant systems to improve low frequency absorption.
• Measurement techniques for absorption.
• Use of absorption in rooms and enclosures.

Vibration control strategies

• Vibration isolation - low and high frequency models.
• Damping treatments. Effects of damping.

2 lectures a week (double period).

Demonstrations include the performance of a simple enclosure, samples of porous materials, a demonstration of vibration isolation, damping, perforation.

Detailed handouts are given that include all material presented in lectures.

Invited lecture by a practising consultant.

Working on a formal assignment that combines elements from across the module to encourage you to apply the knowledge you have gained to a practical problem.

You are encouraged to read supporting texts and a booklist is provided.

Core text

Fundamentals of Noise and Vibration,
1998 Chapter 5, F J Fahy
J G Walker (eds), E&FN Spon
0419227008

Secondary text

Engineering Noise Control
3rd Edition, 2003
2nd Edition, 1996
1st Edition, 1988, D A Bies
C H Hansen, E&FN Spon
3rd edition 0415267145
E&FN Spon
041920430X

Unwin Hyman
0046200215 hdbk
0046200223 pbk

Noise and Vibration Control Engineering, 1992, L L Beranek
I Vér (eds), John Wiley
0471617512
2nd edition 2006

Sound and Structural Vibration, 1985
, F J Fahy, Academic Press
0122476700 HBK
0122476719 pbk
2nd edition 2006 0123736331

Foundations of Engineering Acoustics, 2001, F J Fahy, Academic Press
0122476654