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6 Psychoacoustics 177

Introduction 178

Principal Localization Mechanisms 178

The Minimum Audible Angle 180 Bass Management and Low-Frequency Enhancement

Pyschoacoustics 180 Effects of the Localization Mechanisms on

5.1-Channel Sound 182

The Law of the First Wavefront 184

Phantom Image Stereo 184

Phantom Imaging in Quad 185 Localization, Spaciousness, and Envelopment 187

Lessons from Concert Hall Acoustics 188

Rendering 5 Channels Over 2: Mixdown 188

Auralization and Auditory Virtual Reality 190

Beyond 5.1 191

Addendum: The Use of Surrounds in

Saving Private Ryan 195

Overcoming the Masking Effect 196

Orientation 196

Contrast 197

Movement of Sounds 197

The Limitations of Surrounds 198

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Appendix 1: Sample Rate 201

Conclusion 210

What's Aliasing? 211

Definitions 212

MultiBit and One-Bit Conversion 212

ConverterTests 213

Appendix 2: Word Length, Also Known as

Bit Depth or Resolution 215

Conversion 215

Dither to the Rescue 216

Dynamic Range 218

Actual Performance 220

How Much Performance Is Needed? 221

Oversampling and Noise Shaping 222

The Bottom Line 223 Analog Reference Levels Related to Digital Recording 224

Appendix 3: Music Mostly Formats 227

DigitalTheater Systems CD 227

DVD-Audio 227

Super Audio CD 232

Intellectual Property Protection 232

Towards the Future 233

Index 235

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Preface to the Second Edition

It has been 8 years since the first edition of this book was published. In that time, surround sound has grown enormously overall, but with setbacks for some areas such as surround music since, among other things, the lifestyle that accompanies sitting down and listening to music as a recreation has given way to music on the fly.

In those intervening years, a lot of microphone techniques have been developed that were not in the first edition. Mixing has not been as affected perhaps, but the number of places where it is practiced has grown enormously, and the need to accommodate to older consoles has been reduced as those have been replaced by surround capable ones. Delivery formats have grown and shrunk too, as the marketplace decides on what formats it is going to support. At this writing, HD-DVD and Blu-ray are about 1 year old in the marketplace, and it is not clear whether they will become prominent, or possibly give way to legal Internet downloading of movies, which is just beginning. Nevertheless all newer formats generally support at least the capability of the well-established channel layout 5.1. It is interesting to see the media rush to deliver multichannel formats to the home: over-the-air digital television, HD cable, HD satellite, packaged media from DVD-V through the newer formats, and direct fibre to the home all can have a 5.1-channel soundtrack, so surround sound is with us to stay. Recognizing the current state of sales of surround music, I have retained the information on those formats but put them into an appendix. Chapter 1 explains why I think we may not have heard the final word on surround music, since surround itself has risen from the ashes before, and is now widely successful overall.

Two extremely good surround practitioners have added content for this book, and I am indebted to them. George Massenburg was interviewed in his remarkable studio in Nashville and his interview is available as a web-based addition to this book, and Gary Rydstrom gave me his article on surround in Saving Private Ryan, an extraordinary

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view into his thinking about the surround art, which is the Addendum. Both men are at the top of their fields.

Surround has grown beyond the capability of one person to be expert in all the areas. Thus I have tried to vet the various chapters with help from specific experts in their fields, and to consider and reflect their expert opinions. However, the final text is mine.Those particularly helpful to me, in the order of what they did in this book, were FloydToole, Florian Camerer, Bob Ludwig, Lorr Kramer, Roger Dressier, and Stanley Lipshitz. My colleague at USC Martin Krieger read the text so that I could understand how it would be understood from someone outside the professional audio field, and he provided useful insights.

As always, I am indebted to my life partner Friederich Koenig, who alternately drives me to do it, and finds that I spend too much time in front of the computer.

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