MANUAL OF ANALOGUE SOUND RESTORATION ... - British Library

Analogue Sound Restoration Techniques
8.8 Reducing background noise .............................................................................................................194
9 Reciprocal noise reduction.....................................................................................................................196
9.1 Principles of noise reduction .............................................................................................................196
9.2 Non-reciprocal and reciprocal noise-reduction..................................................................................196
9.3 Recognising reciprocal noise reduction systems ................................................................................197
9.4 Principles of reciprocal noise reduction systems ................................................................................198
9.5 Dolby “A”........................................................................................................................................199
9.6 Dolby “B” ........................................................................................................................................201
9.7 DBX systems.....................................................................................................................................202
9.8 JVC ANRS (Audio Noise Reduction System) .....................................................................................205
9.9 Telcom C4........................................................................................................................................205
9.10 Telefunken “High-Com”.............................................................................................................206
9.11 The “CX” systems.......................................................................................................................206
9.12 Dolby “C”...................................................................................................................................207
9.13 Dolby SR and Dolby S .................................................................................................................208
9.14 Other noise reduction systems ....................................................................................................209
9.15 Noise reduction systems not needing treatment..........................................................................211
9.16 Conclusion ..................................................................................................................................211
10 Spatial recordings ..................................................................................................................................213
10.1 Introduction ................................................................................................................................213
10.2 “Two-channel” recordings..........................................................................................................213
10.3 Archaeological stereo ..................................................................................................................216
10.4 Matrixing into two channels........................................................................................................218
10.5 Three-channel recordings............................................................................................................218
10.6 Four-channel recordings - in the cinema .....................................................................................219
10.7 Four-channel audio-only principles..............................................................................................220
10.8 Matrix “quadraphonic” systems..................................................................................................221
10.9 The QS system ............................................................................................................................221
10.10 The SQ system ............................................................................................................................222
10.11 Matrix H .....................................................................................................................................223
10.12 “Dolby Stereo” ...........................................................................................................................224
10.13 Developments of “Dolby Stereo” - (a) Dolby AC-3 ....................................................................226
10.14 Developments of “Dolby Stereo” - (b) Dolby headphone ...........................................................227
10.15 Developments of “Dolby Stereo” - (c) Pro Logic 2......................................................................227
10.16 Discrete 4-channel systems - The JVC CD-4 system....................................................................227
10.17 The “UD-4” system ....................................................................................................................228
10.18 “Ambisonics”..............................................................................................................................229
10.19 Other discrete four-channel media..............................................................................................230
10.20 More than five-channel systems..................................................................................................230
10.21 Multitrack master-tapes ..............................................................................................................231
11 Dynamics...............................................................................................................................................233
11.1 Introduction ................................................................................................................................233
11.2 The reasons for dynamic compression .........................................................................................234
11.3 Acoustic recording.......................................................................................................................235
11.4 Manually-controlled electrical recording......................................................................................235
11.5 Procedures for reversing manual control .....................................................................................237
11.6 Automatic volume controlling .....................................................................................................238
11.7 Principles of limiters and compressors..........................................................................................241
11.8 Identifying limited recordings ......................................................................................................243
11.9 Attack times ................................................................................................................................244
11.10 Decay-times ................................................................................................................................245
11.11 The compression-ratio and how to kludge It ...............................................................................246
12 Acoustic recordings ...............................................................................................................................249
12.1 Introduction ................................................................................................................................249
12.2 Ethical matters.............................................................................................................................249
12.3 Overall view of acoustic recording hardware...............................................................................251
12.4 Performance modifications..........................................................................................................252
12.5 Procedures for reverse-engineering the effects............................................................................254
12.6 Documentation of HMV acoustic recording equipment...............................................................255
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