Introduction to Acoustics

By Simone Malacrida

The following topics are presented in this book:
introduction to waves and their properties
acoustic waves
human acoustics and phonometric systems
room acoustics and hints of building acoustic design

• Language: English
• Publisher: Simone Malacrida
• Release date: Dec 21, 2022
• ISBN: 9798201753382

Simone Malacrida

Simone Malacrida (1977) Ha lavorato nel settore della ricerca (ottica e nanotecnologie) e, in seguito, in quello industriale-impiantistico, in particolare nel Power, nell'Oil&Gas e nelle infrastrutture. E' interessato a problematiche finanziarie ed energetiche. Ha pubblicato un primo ciclo di 21 libri principali (10 divulgativi e didattici e 11 romanzi) + 91 manuali didattici derivati. Un secondo ciclo, sempre di 21 libri, è in corso di elaborazione e sviluppo.

Book preview

Introduction to Acoustics

SIMONE MALACRIDA

The following topics are presented in this book:

introduction to waves and their properties

acoustic waves

human acoustics and phonometric systems

room acoustics and hints of building acoustic design

Simone Malacrida (1977)

Engineer and writer, has worked on research, finance, energy policy and industrial plants.

ANALYTICAL INDEX

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INTRODUCTION

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I – THE WAVES

Definitions

Wave equation

Waves on a rope

Sound waves in a gas

harmonic waves

Fourier series decomposition

Spherical waves

Wave properties

Standing waves e

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II - HUMAN ACOUSTIC

Ear um no

Phonometry

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III - APPLIED ACOUSTICS

Sound absorbing materials

Environmental acoustics

The noise

INTRODUCTION

This book presents a broad overview of acoustic phenomena, starting from the physical foundations, given by the properties of waves.

The mathematical and physical characteristics of the waves are analysed, especially as regards the acoustic ones, which require a means of propagation.

Subsequently, a detailed description of the human ear and how our body perceives and processes sounds will be provided, to then move on to phonometric and acoustic measurement systems.

Finally, all aspects of applied acoustics will not be forgotten, from the choice of sound-absorbing materials to the design of rooms with particular acoustics, passing through practical and empirical cases.

A final mention will be dedicated to noise abatement.

To understand this manual, it is necessary to have mathematical pre-requisites based on mathematical analysis, especially as regards Fourier series, the concepts of integral and differential equation.

I

THE WAVES

Definitions

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A wave is a perturbation, periodic or impulsive, which propagates with a defined speed.

The waves originate from a source that produces the disturbance.

There are many types of waves: waves of mechanical origin, such as elastic waves (eg sound waves in a gas), or seismic waves generated in earthquakes, or waves on the surface of a liquid.

All these types of waves can only propagate in the presence of a medium and are generated by the vibration of a source which sets the particles of the surrounding medium in motion.

Then there are the electromagnetic waves, generated by a motion of electric charges; for their propagation they do not need the support of a medium, but they can also propagate in a vacuum.

Although the wave propagates in a medium, there is no net transport of matter: the atoms or molecules of the medium are set in motion and oscillate around equilibrium positions.

Instead, the wave carries momentum and energy.

The wave is described as the perturbation, with respect to the equilibrium configuration, of an appropriate field; the field can be scalar (eg pressure field for sound waves), or vectorial (eg electromagnetic field for electromagnetic waves).

We describe the field perturbation as a function of the spatial coordinates x, y, z, and time t.

This function can be periodic or impulsive .

However, if it has to account for a phenomenon that moves with speed v , the spatial and temporal coordinates must satisfy a suitable condition.

Any function like:

describes a wave that propagates with speed v along the x axis , in one