Acoustics: Sound Fields and Transducers

Preface

Acknowledgements

Chapter 1. Introduction and terminology

Part I Introduction

1.2 What is sound?

1.3 Propagation of sound through gas

1.4 Measurable aspects of sound

Part II: Terminology

1.5 General

1.6 Standard International (SI) units

1.7 Pressure and density

1.8 Speed and velocity

1.9 Impedance

1.10 Intensity, energy density, and levels

Notes

Chapter 2. The wave equation and solutions

Part III The Wave Equation

2.2 Derivation of the wave equation

Part IV Solutions of the Wave Equation in One Dimension

2.4 Solution of wave equation for air in a tube terminated by an impedance

2.5 Solution of wave equation for air in a tube filled with absorbent material

2.6 Freely traveling plane wave

2.7 Freely traveling cylindrical wave

2.8 Freely traveling spherical wave

Part V Solutions of the Helmholtz Wave Equation in three Dimensions

2.10 Cylindrical coordinates

2.11 Spherical coordinates

Notes

Chapter 3. Electro-mechano-acoustical circuits

Part VI Mechanical circuits

3.2 Physical and mathematical meanings of circuit elements

3.3 Mechanical elements

Part VII Acoustical circuits

Part VIII Transducers

3.5 Electromechanical transducers

3.6 Mechano-acoustic transducer

3.7 Examples of transducer calculations

Part IX Circuit theorems, energy, and power

3.8 Conversion from admittance-type analogies to impedance-type analogies

3.9 Thévenin’s theorem

3.10 Transducer impedances

Notes

Chapter 4. Acoustic components

4.1 Introduction

Part X Acoustic elements

4.3 Acoustic compliances

4.4 Acoustic resistances

4.5 Cavity with holes on opposite sides—mixed mass-compliance element

4.6 Intermediate-sized tube—mixed mass-resistance element [a (in meters)>0.01/ and a<10/f] [2]

4.7 Perforated sheet—mixed mass-resistance element[a (in meters)>0.01/ and a<10/f] [2]

4.8 Acoustic transformers

Part XI Elementary reflection and radiation of sound

4.9 Reflection of a plane wave from a plane

4.10 Radiation from a pulsating sphere

4.11 Radiation from a monopole point source (simple source)

4.12 Combination of point sources in phase

4.13 Steered beam-forming array of point sources

4.14 Dipole point source (doublet)

4.15 Radiation from an oscillating sphere

Part XII Directivity index

Part XIII Radiation impedances

4.18 Oscillating sphere

4.19 Plane circular piston in infinite baffle

4.20 Plane circular free disk

4.21 Plane circular piston radiating from one side only in free space

Part XIV Viscous and thermal losses

4.23 Wave equation for an infinite lossy tube

Notes

Chapter 5. Microphones

Part XV General characteristics of microphones

5.1 Pressure microphones

5.2 Pressure-gradient microphones

5.3 Combination pressure and pressure-gradient microphones

Part XVI Pressure microphones

5.4 Electromagnetic moving-coil microphone (dynamic microphone)

5.5 Electrostatic microphone (capacitor microphone)

Part XVII Pressure-Gradient microphones

Part XVIII Combination microphones

5.8. Acoustical combination of pressure and pressure-gradient microphones

5.9. Dual-diaphragm combination of pressure and pressure-gradient microphones

Notes

Chapter 6. Electrodynamic loudspeakers

Part XIX Basic theory of electrodynamic loudspeakers

6.2 Construction [2]

6.3 Electro-mechano-acoustical circuit

6.4 Power output

6.5 Thiele–Small parameters [5]

6.6 Sound pressure produced at distance r

6.7 Frequency-response curves

6.8 Electrical input impedance

6.9 Efficiency

6.10 Measurement of Thiele–Small parameters

6.11 Examples of loudspeaker calculations

Part XX Design factors affecting direct-radiator loudspeaker performance

6.12 Magnet size

6.13 Voice-coil design

6.14 Diaphragm behavior

6.15 Directivity characteristics

6.16 Transfer functions and the Laplace transform

6.17 Transient response

6.18 Nonlinearity [14]

References

Chapter 7. Loudspeaker systems

Part XXI Simple enclosures

7.1 Brief summary of common loudspeaker systems

7.2 Unbaffled direct-radiator loudspeaker

7.3 Infinite baffle

7.4 Finite-sized flat baffle

7.5 Open-back cabinets

7.6 Closed-box baffle [1,2]

7.7 Measurement of baffle constants

Part XXII Bass-reflex enclosures

7.9 Acoustical circuit

7.10 Electro-mechano-acoustical circuit

7.11 Radiated sound

7.12 Alignments for predetermined frequency-response shapes

7.13 Port dimensions

7.14 Diaphragm displacement

7.15 Electrical input impedance and evaluation of QL

7.16 Performance

7.17 Construction and adjustment notes

Part XXIII 2-port network for small enclosures

7.18 2-port network for a bass-reflex enclosure

Part XXIV Transmission-line enclosures

Part XXV Multiple drive units

7.21 Dual concentric drive units

References

Chapter 8. Cellphone acoustics

Part XXVI Acoustical transducers for cellphones

8.1 Loudspeaker and microphone

8.2 Circuit diagram for a cellphone loudspeaker

8.3 Design considerations

8.4 Head and torso simulator

8.5 Microphones

Part XXVII Type approval testing of cellphones

8.6 Measurements for type approval

References

Chapter 9. Horn loudspeakers

Part XXVIII Horn drive units

9.2 Electro-mechano-acoustical circuit [1]

9.3 Reference efficiency

9.4 Frequency response

9.5 Examples of horn calculations

Part XXIX Horns

9.7 Possible profiles [2]

9.8 Mouth size

9.9 Infinite parabolic horn [11]

9.10 Infinite conical horn

9.11 Infinite exponential horn

9.12 Infinite hyperbolic horn (hypex) [12]

9.13 Finite horns

9.14 Bends in horns

9.15 Cross-sectional shapes

9.16 Materials

References

Chapter 10. Sound in enclosures

Part XXX Sound Fields in Small, Regularly Shaped Enclosures

10.2 Stationary and standing waves

10.3 Normal modes and normal frequencies

10.4 Steady-state and transient sound pressures

10.5 Examples of rectangular enclosures

Part XXXI Sound in Large Enclosures

10.7 The reverberation equations

10.8 Air absorption

10.9 Total steady sound-pressure level

10.10 Optimum reverberation time

10.11 Sound Strength G

10.12 Early and reverberant sound in concert halls

10.13 Distance for equality of direct and reverberant sound fields

10.14 Sound levels for speech and music

References

Chapter 11. Room design for loudspeaker listening

Part XXXII Home room design

11.2 Listening room acoustics

References

Chapter 12. Radiation and scattering of sound by the boundary value method

Part XXXIII Radiation in cylindrical coordinates

12.2 Radiation from an infinite line source

Part XXXIV Radiation and scattering in spherical coordinates

12.4 Scattering from a rigid sphere by a point source

12.5 Radiation from a point source on a sphere

12.6 Radiation from a spherical cap in a sphere

12.7 Radiation from a rectangular cap in a sphere

12.8 Radiation from a piston in a sphere

12.9 Radiation from an oscillating convex dome in an infinite baffle

12.10 Radiation from an oscillating concave dome in an infinite baffle

References

Chapter 13. Radiation and scattering of sound by the boundary integral method

Part XXXV Boundary integrals and the Green’s function

13.2 The Rayleigh integrals and Green’s function

13.3 The Kirchhoff–Helmholtz boundary integral

13.4 The Green’s function in different coordinate systems

13.5 Boundary integral method case study: Radially pulsating cap in a rigid sphere

13.6 Reflection of a point source from a plane

Part XXXVI Radiation and scattering in cylindrical-spherical coordinates

13.8 Radiation from a resilient circular disk without a baffle [16]

13.9 Radiation from a resilient disk in an infinite baffle [19]

13.10 Radiation from a rigid circular piston in a finite circular open baffle [23, 24]

13.11 Radiation from a rigid circular piston in a finite circular closed baffle [30] (one-sided radiator)

13.12 The Babinet–Bouwkamp principle

Part XXXVII Radiation theorems, radiation in rectangular-spherical coordinates, mutual impedance

13.14 Radiation from an infinitely long oscillating strip in an infinite baffle [36,37]

13.15 The far-field pressure distribution as a spatial frequency spectrum of the source velocity distribution

13.16 The bridge product theorem

13.17 Radiation from a rigid rectangular piston in an infinite baffle [38,39]

13.18 Mutual radiation impedance between rigid circular pistons in an infinite baffle [40]

13.19 Near-field acoustical holography [41]

13.20 Time-reversal

References

Chapter 14. State variable analysis of circuits

14.1 A brief history

14.2 What is state variable analysis?

14.3 Why use state variable analysis?

14.4 What are the restrictions?

14.5 Some basic circuit theory

14.6 Graph theory

14.7 Worked example No. 1: Loudspeaker in an enclosure with a bass-reflex port

14.8 Solution of the worked example using the Faddeev–Leverrier algorithm [10]

14.9 Far-field on-axis pressure

14.10 Worked example No. 2: Loudspeaker in an enclosure with a bass-reflex port using the Norton equivalent source

14.11 Worked example No. 3: Loudspeaker in an enclosure with a bass-reflex port using a transformer and gyrator

14.12 Worked example No. 4: Loudspeaker in an enclosure with a bass-reflex port using controlled sources

14.13 Gyrator comprising two current-controlled voltage sources

References

Appendix I. Frequency-response shapes for loudspeakers [1]

Appendix II. Mathematical formulas [1,2]

Appendix III. Conversion factors

Index