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Audio Engineering

(Barry) #1

  • I: Fundamentals of Sound .................................................................................................. About the Authors .............................................................................................................xv

  • Chapter 1: Audio Principles ...............................................................................................

  • 1.1 The Physics of Sound ................................................................................................

  • 1.2 Wavelength

  • 1.3 Periodic and Aperiodic Signals .................................................................................

  • 1.4 Sound and the Ear ......................................................................................................

  • 1.5 The Cochlea

  • 1.6 Mental Processes .....................................................................................................

  • 1.7 Level and Loudness .................................................................................................

  • 1.8 Frequency Discrimination........................................................................................

  • 1.9 Frequency Response and Linearity ..........................................................................

  • 1.10 The Sine Wave .........................................................................................................

  • 1.11 Root Mean Square Measurements ...........................................................................

  • 1.12 The Decibel

  • 1.13 Audio Level Metering ..............................................................................................

  • References ................................................................................................................

  • Chapter 2: Measurement ..................................................................................................

  • 2.1 Concepts Underlying the Decibel and its Use in Sound Systems ...........................

  • 2.2 Measuring Electrical Power .....................................................................................

  • 2.3 Expressing Power as an Audio Level ......................................................................

  • 2.4 Conventional Practice ..............................................................................................

  • 2.5 The Decibel in Acoustics—LP,LW, and LI ..............................................................

    • and Acoustic Pressure Level (LP) ............................................................................ 2.6 Acoustic Intensity Level (LI), Acoustic Power Level (LW),



  • 2.7 Inverse Square Law ..................................................................................................

  • 2.8 Directivity Factor .....................................................................................................

  • 2.9 Ohm’s Law .............................................................................................................. vi Contents

  • 2.10 A Decibel is a Decibel is a Decibel .........................................................................

  • 2.11 Older References .....................................................................................................

  • 2.12 The Equivalent Level (LEQ) in Noise Measurements ..............................................

  • 2.13 Combining Decibels ................................................................................................

  • 2.14 Combining Voltage ..................................................................................................

  • 2.15 Using the Log Charts ...............................................................................................

  • 2.16 Finding the Logarithm of a Number to Any Base ...................................................

  • 2.17 Semitone Intervals ...................................................................................................

  • 2.18 System Gain Changes ..............................................................................................

  • 2.19 The VU and the Volume Indicator Instrument ........................................................

  • 2.20 Calculating the Number of Decades in a Frequency Span ......................................

  • 2.21 Defl ection of the Eardrum at Various Sound Levels ...............................................

  • 2.22 The Phon ..................................................................................................................

  • 2.23 The Tempered Scale ................................................................................................

  • 2.24 Measuring Distortion ...............................................................................................

  • 2.25 The Acoustical Meaning of Harmonic Distortion ...................................................

  • 2.26 Playback Systems in Studios ...................................................................................

  • 2.27 Decibels and Percentages ........................................................................................

  • 2.28 Summary .................................................................................................................7

  • Further Reading .......................................................................................................

  • Chapter 3: Acoustic Environment ....................................................................................

  • 3.1 The Acoustic Environment ......................................................................................

  • 3.2 Inverse Square Law .................................................................................................

  • 3.3 Atmospheric Absorption .........................................................................................

  • 3.4 Velocity of Sound ....................................................................................................

  • 3.5 Temperature-Dependent Velocity ............................................................................

  • 3.6 The Effect of Altitude on the Velocity of Sound in Air ..........................................

  • 3.7 Typical Wavelengths ................................................................................................

  • 3.8 Doppler Effect .........................................................................................................

  • 3.9 Refl ection and Refraction ........................................................................................

  • 3.10 Effect of a Space Heater on Flutter Echo ................................................................

  • 3.11 Absorption

  • 3.12 Classifying Sound Fields .........................................................................................

  • 3.13 The Acoustic Environment Indoors ...................................................................... Contents vii

  • 3.14 Conclusion ............................................................................................................

  • Further Reading.....................................................................................................

  • II: Audio Electronics .......................................................................................................11

  • Chapter 4: Components ..................................................................................................

  • 4.1 Building Block Components .................................................................................

  • Chapter 5: Power Supply Design ....................................................................................

  • 5.1 High Power Systems .............................................................................................

  • 5.2 Solid-State Rectifi ers.............................................................................................

  • 5.3 Music Power..........................................................................................................

  • 5.4 Infl uence of Signal Type on Power Supply Design ..............................................

  • 5.5 High Current Power Supply Systems ....................................................................

  • 5.6 Half-Wave and Full-Wave Rectifi cation ...............................................................

  • 5.7 Direct Current Supply Line Ripple Rejection .......................................................

  • 5.8 Voltage Regulator Systems ...................................................................................

  • 5.9 Series Regulator Layouts ......................................................................................

  • 5.10 Overcurrent Protection ..........................................................................................

  • 5.11 Integrated Circuit (Three Terminals) Voltage Regulator ICs ................................

  • 5.12 Typical Contemporary Commercial Practice ........................................................

  • 5.13 Battery Supplies ....................................................................................................

  • 5.14 Switch-Mode Power Supplies ...............................................................................

  • Reference ..............................................................................................................

  • III: Preamplifi ers and Amplifi ers ...................................................................................

  • Chapter 6: Introduction to Audio Amplifi cation............................................................

  • Chapter 7: Preamplifi ers and Input Signals ..................................................................

  • 7.1 Requirements ........................................................................................................

  • 7.2 Signal Voltage and Impedance Levels ..................................................................

  • 7.3 Gramophone Pick-Up Inputs ................................................................................

  • 7.4 Input Circuitry .......................................................................................................

  • 7.5 Moving Coil Pick-up Head Amplifi er Design ......................................................

  • 7.6 Circuit Arrangements ............................................................................................

  • 7.7 Input Connections ................................................................................................. viii Contents

  • 7.8 Input Switching .....................................................................................................

  • 7.9 Preamplifi er Stages ...............................................................................................

  • 7.10 Linearity

  • 7.11 Noise Levels ..........................................................................................................

  • 7.12 Output Voltage Characteristics ..............................................................................

  • 7.13 Voltage Amplifi er Design ......................................................................................

  • 7.14 Constant-Current Sources and “Current Mirrors” ................................................

  • 7.15 Performance Standards .........................................................................................

  • 7.16 Audibility of Distortion .........................................................................................

  • 7.17 General Design Considerations .............................................................................

  • 7.18 Controls

  • References .............................................................................................................

  • Chapter 8: Interfacing and Processing ..........................................................................

  • 8.1 The Input ...............................................................................................................24

  • 8.2 Radio Frequency Filtration ...................................................................................

  • 8.3 Balanced Input ......................................................................................................

  • 8.4 Subsonic Protection and High-Pass Filtering ........................................................

  • 8.5 Damage Protection ................................................................................................

  • 8.6 What Are Process Functions? ...............................................................................

  • 8.7 Computer Control .................................................................................................

  • References .............................................................................................................

  • Chapter 9: Audio Amplifi ers ...........................................................................................

  • 9.1 Junction Transistors ..............................................................................................

  • 9.2 Control of Operating Bias .....................................................................................

  • 9.3 Stage Gain .............................................................................................................

  • 9.4 Basic Junction Transistor Circuit Confi gurations .................................................

  • 9.5 Emitter–Follower Systems ....................................................................................

  • 9.6 Thermal Dissipation Limits ..................................................................................

  • 9.7 Junction Field Effect Transistors ( JFETs) ............................................................

  • 9.8 Insulated Gate FETs (MOSFETs) .........................................................................

  • 9.9 Power BJTs vs Power MOSFETs as Amplifi er Output Devices ..........................

  • 9.10 U and D MOSFETs ...............................................................................................

  • 9.11 Useful Circuit Components ...................................................................................

  • 9.12 Circuit Oddments .................................................................................................. Contents ix

  • 9.13 Slew Rate Limiting ...............................................................................................

  • References .............................................................................................................

  • Chapter 10: Audio Amplifi er Performance ....................................................................

  • 10.1 A Brief History of Amplifi ers ...............................................................................

  • 10.2 Amplifi er Architectures.........................................................................................

  • 10.3 The Three-Stage Architecture ...............................................................................

  • 10.4 Power Amplifi er Classes .......................................................................................

  • 10.5 AC- and DC-Coupled Amplifi ers ..........................................................................

  • 10.6 Negative Feedback in Power Amplifi ers ...............................................................

  • References .............................................................................................................

  • Chapter 11: Valve (Tube-Based) Amplifi ers ...................................................................

  • 11.1 Valves or Vacuum Tubes .......................................................................................

  • 11.2 Solid-State Devices ...............................................................................................

  • 11.3 Valve Audio Amplifi er Layouts ............................................................................

  • 11.4 Single-Ended Versus Push–Pull Operation ...........................................................

  • 11.5 Phase Splitters .......................................................................................................

  • 11.6 Output Stages ........................................................................................................

  • 11.7 Output (Load-Matching) Transformer ..................................................................

  • 11.8 Effect of Output Load Impedance .........................................................................

  • 11.9 Available Output Power ........................................................................................

  • References .............................................................................................................

  • Chapter 12: Negative Feedback ......................................................................................

  • 12.1 Amplifi er Stability and Negative Feedback ..........................................................

  • 12.2 Maximizing Negative Feedback ............................................................................

  • 12.3 Maximizing Linearity Before Feedback ...............................................................

  • Further Reading.....................................................................................................

  • Chapter 13: Noise and Grounding .................................................................................

  • 13.1 Audio Amplifi er Printed Circuit Board Design ....................................................

  • 13.2 Amplifi er Grounding .............................................................................................

  • 13.3 Ground Loops: How They Work and How to Deal with Them ............................

  • 13.4 Class I and Class II................................................................................................

  • 13.5 Mechanical Layout and Design Considerations....................................................

  • IV: Digital Audio x Contents

  • Chapter 14: Digital Audio Fundamentals ......................................................................

  • 14.1 Audio as Data ........................................................................................................

  • 14.2 What is an Audio Signal?......................................................................................

  • 14.3 Why Binary? .........................................................................................................

  • 14.4 Why Digital? .........................................................................................................

  • 14.5 Some Digital Audio Processes Outlined ...............................................................

  • 14.6 Time Compression and Expansion ........................................................................

  • 14.7 Error Correction and Concealment .......................................................................

  • 14.8 Channel Coding.....................................................................................................

  • 14.9 Audio Compression...............................................................................................

  • 14.10 Disk-Based Recording ..........................................................................................

  • 14.11 Rotary Head Digital Recorders .............................................................................

  • 14.12 Digital Audio Broadcasting ..................................................................................

  • 14.13 Networks ...............................................................................................................4

  • References .............................................................................................................

  • Chapter 15: Representation of Audio Signals................................................................

  • 15.1 Introduction ...........................................................................................................43

  • 15.2 Analogue and Digital ............................................................................................

  • 15.3 Elementary Logical Processes ..............................................................................

  • 15.4 The Signifi cance of Bits and Bobs ........................................................................

  • 15.5 Transmitting Digital Signals .................................................................................

  • 15.6 The Analogue Audio Waveform ...........................................................................

  • 15.7 Arithmetic .............................................................................................................45

  • 15.8 Digital Filtering .....................................................................................................

  • 15.9 Other Binary Operations .......................................................................................

  • 15.10 Sampling and Quantizing ......................................................................................

  • 15.11 Transform and Masking Coders ............................................................................

  • References .............................................................................................................

  • Chapter 16: Compact Disc ..............................................................................................

  • 16.1 Problems with Digital Encoding ...........................................................................

  • 16.2 The Record-Replay System ..................................................................................

  • 16.3 The Replay System ...............................................................................................

  • 16.4 Error Correction .................................................................................................... Contents xi

  • References .............................................................................................................

  • Chapter 17: Digital Audio Recording Basics .................................................................

  • 17.1 Types of Media ......................................................................................................

  • 17.2 Recording Media Compared .................................................................................

  • 17.3 Some Digital Audio Processes Outlined ...............................................................

  • 17.4 Hard Disc Recorders .............................................................................................

  • 17.5 The PCM Adaptor .................................................................................................

  • 17.6 An Open Reel Digital Recorder ............................................................................

  • 17.7 Rotary Head Digital Recorders .............................................................................

  • 17.8 Digital Compact Cassette ......................................................................................

  • 17.9 Editing Digital Audio Tape ...................................................................................

  • References .............................................................................................................

  • Chapter 18: Digital Audio Interfaces .............................................................................

  • 18.1 Digital Audio Interfaces ........................................................................................

  • 18.2 MADI (AES10–1991) Serial Multichannel Audio Digital Interface ....................

  • Chapter 19: Data Compression ......................................................................................

  • 19.1 Lossless Compression ...........................................................................................

  • 19.2 Intermediate Compression Systems ......................................................................

  • 19.3 Psychoacoustic Masking Systems .........................................................................

  • 19.4 MPEG Layer 1 Compression (PASC) ...................................................................

  • 19.5 MPEG Layer 2 Audio Coding (MUSICAM) ........................................................

  • 19.6 MPEG Layer 3 ......................................................................................................

  • 19.7 MPEG-4 ................................................................................................................

  • 19.8 Digital Audio Production ......................................................................................

  • Chapter 20: Digital Audio Production ...........................................................................

  • 20.1 Digital Audio Workstations (DAWs) ....................................................................

  • 20.2 Audio Data Files ...................................................................................................

  • 20.3 Sound Cards ..........................................................................................................

  • 20.4 PCI Bus Versus ISA Bus .......................................................................................

  • 20.5 Disks and Other Peripheral Hardware ..................................................................

  • 20.6 Hard Drive Interface Standards .............................................................................

  • 20.7 Digital Noise Generation—Chain Code Generators ............................................. xii Contents

  • References .............................................................................................................

  • Chapter 21: Other Digital Audio Devices ......................................................................

  • 21.1 Video Recorders ....................................................................................................

  • 21.2 High Defi nition Compatible Digital (HDCD) .......................................................

  • 21.3 CD Writers ............................................................................................................

  • 21.4 MPEG Systems .....................................................................................................

  • 21.5 MP3 .......................................................................................................................

  • 21.6 Transcribing a Recording by Computer ................................................................

  • 21.7 WAV Onward ........................................................................................................

  • 21.8 DAM CD ...............................................................................................................

  • 21.9 DVD and Audio ....................................................................................................

  • V: Microphone and Loudspeaker Technology ...............................................................

  • Chapter 22: Microphone Technology .............................................................................

  • 22.1 Microphone Sensitivity .........................................................................................

  • 22.2 Microphone Selection ...........................................................................................

  • 22.3 Nature of Response and Directional Characteristics .............................................

  • 22.4 Wireless Microphones ...........................................................................................

  • 22.5 Microphone Connectors, Cables, and Phantom Power .........................................

  • 22.6 Measurement Microphones ...................................................................................

  • Further Reading.....................................................................................................

  • Chapter 23: Loudspeakers ..............................................................................................

  • 23.1 Radiation of Sound................................................................................................

  • 23.2 Characteristic Impedance ......................................................................................

  • 23.3 Radiation Impedance.............................................................................................

  • 23.4 Radiation from a Piston.........................................................................................

  • 23.5 Directivity .............................................................................................................6

  • 23.6 Sound Pressure Produced at Distance r ................................................................

  • 23.7 Electrical Analogue ...............................................................................................

  • 23.8 Diaphragm/Suspension Assembly ........................................................................

  • 23.9 Diaphragm Size .....................................................................................................

  • 23.10 Diaphragm Profi le .................................................................................................

  • 23.11 Straight-Sided Cones.............................................................................................

  • 23.12 Material ................................................................................................................. Contents xiii

  • 23.13 Soft Domes ............................................................................................................69

  • 23.14 Suspensions ...........................................................................................................69

  • 23.15 Voice Coil

  • 23.16 Moving Coil Loudspeaker.....................................................................................

  • 23.17 Motional Impedance .............................................................................................

  • Further Reading.....................................................................................................

  • Chapter 24: Loudspeaker Enclosures ............................................................................

  • 24.1 Loudspeakers ........................................................................................................

  • 24.2 The Interrelation of Components ..........................................................................

  • Chapter 25: Headphones ................................................................................................

  • 25.1 A Brief History......................................................................................................

  • 25.2 Pros and Cons of Headphone Listening ................................................................

  • 25.3 Headphone Types ..................................................................................................

  • 25.4 Basic Headphone Types ........................................................................................

  • 25.5 Measuring Headphones .........................................................................................

  • 25.6 The Future .............................................................................................................74

  • VI: Sound Reproduction Systems ..................................................................................

  • Chapter 26: Tape Recording ...........................................................................................

  • 26.1 Introduction ...........................................................................................................74

  • 26.2 Magnetic Theory ...................................................................................................

  • 26.3 The Physics of Magnetic Recording .....................................................................

  • 26.4 Bias........................................................................................................................

  • 26.5 Equalization ..........................................................................................................

  • 26.6 Tape Speed ............................................................................................................

  • 26.7 Speed Stability ......................................................................................................

  • 26.8 Recording Formats—Analogue Machines ............................................................

  • Chapter 27: Recording Consoles ....................................................................................

  • 27.1 Introduction ...........................................................................................................76

  • 27.2 Standard Levels and Level Meters ........................................................................

  • 27.3 Standard Operating Levels and Line-Up Tones ....................................................

  • 27.4 Digital Line-Up .....................................................................................................

  • 27.5 Sound Mixer Architecture and Circuit Blocks ...................................................... xiv Contents

  • 27.6 Audio Mixer Circuitry ..........................................................................................

  • 27.7 Mixer Automation .................................................................................................

  • 27.8 Digital Consoles ....................................................................................................

  • References .............................................................................................................

  • Chapter 28: Video Synchronization ...............................................................................

  • 28.1 Introduction ...........................................................................................................80

  • 28.2 Persistence of Vision .............................................................................................

  • 28.3 Cathode Ray Tube and Raster Scanning ...............................................................

  • 28.4 Television Signal ...................................................................................................

  • 28.5 Color Perception ...................................................................................................

  • 28.6 Color Television ....................................................................................................

  • 28.7 Analogue Video Interfaces ....................................................................................

  • 28.8 Digital Video .........................................................................................................

  • 28.9 Embedded Digital Audio in the Digital Video Interface .......................................

  • 28.10 Time Code .............................................................................................................83

  • Chapter 29: Room Acoustics ..........................................................................................

  • 29.1 Introduction ...........................................................................................................84

  • 29.2 Noise Control ........................................................................................................

  • 29.3 Studio and Control Room Acoustics .....................................................................

  • VII: Audio Test and Measurement .................................................................................

  • Chapter 30: Fundamentals and Instruments .................................................................

  • 30.1 Instrument Types ...................................................................................................

  • 30.2 Signal Generators ..................................................................................................

  • 30.3 Alternative Waveform Types .................................................................................

  • 30.4 Distortion Measurement ........................................................................................

  • Index ...............................................................................................................................

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