Noise Control

From Concept to Application

Colin H. Hansen, Kristy L. Hansen

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9780429768293
• Edition: 2
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie de l'acoustique

The second edition of Noise Control: From Concept to Application, newly expanded and thoroughly updated, now includes 180 graded problems with solutions, plus 100 end-of-chapter problems with solutions available for instructors on the authors' website. Working from basic scientific principles, the authors show how an understanding of sound can be applied to real-world settings, working through numerous examples in detail and covering good practice in noise control for both new and existing facilities.

It covers the essential topics for industrial noise control: acoustics, noise criteria, hearing-damage risk, noise-assessment measures, measurement instrumentation, sound-source types including the calculation and measurement of their output power, sound propagation outdoors, sound in rooms, sound-absorbing materials, sound transmission through partitions and enclosures, noise barriers, reactive and dissipative muffler-noise reduction and muffler-design considerations such as pressure loss and self-noise generation.

Detailed explanations of important concepts make this textbook easy to understand by engineering and science undergraduates, as well as professionals with no background in acoustics.

Authors' website: www.causalsystems.com

Colin H. Hansen is Emeritus Professor in Mechanical Engineering at the University of Adelaide, Australia, and past President of the International Institute of Acoustics and Vibration.

Kristy L. Hansen is a Senior Lecturer in Mechanical Engineering at Flinders University, Australia, and holder of the Australian Research Council's Discovery Early Career Researcher Award.

1

Fundamentals

LEARNING OBJECTIVES

In this chapter, the reader is introduced to:

• fundamentals and basic terminology of noise control;
• noise-control strategies for new and existing facilities;
• the speed of sound and the wave equation;
• plane and spherical waves;
• energy density; sound intensity and sound power;
• decibels and sound pressure level;
• frequency analysis and sound spectra;
• adding and subtracting sound pressure levels and combining level reductions; and
• three kinds of impedance.

1.1 Introduction

The World Health Organisation (Goelzer et al., 2000) has recognised noise as the most significant health hazard to the working population in terms of the number of people affected. In many industries there is much that can be done to alleviate harmful noise. Perhaps the most insidious aspect of noise-induced hearing loss is that in most cases, damage accumulates over time and is only recognised as a problem when it is too late to do anything about it.

Noise can also affect our daily living away from the work place. This type of problem is called environmental noise pollution and it is unhealthy for us in terms of our psychological well-being, which in turn can affect our physical health. In this context, noise is defined as sound that is unwanted by one or more individuals, even though it may be wanted by someone else.

When considering noise control, it is well-known that the most cost-effective solution to a problem is often to control the noise-generating mechanism right at its source. This often has the added benefit of making the process more efficient in addition to being less noisy. However, it is often (although not always) only manufacturers of equipment who can alter the noise-generating processes in their equipment, which leaves the engineer who is responsible for an existing item of noisy machinery to find some other way of reducing the noise that reaches places or people where it is either a hazard or unwanted. Often this treatment takes the form of enclosures, barriers, mufflers or vibration isolation and is referred to as “add-on” noise-control...