MANUAL OF ANALOGUE SOUND RESTORATION ... - British Library

1 Introduction
1.1 The organisation of this manual
This manual gives details of some of the techniques to be followed when old sound
recordings are transferred to more modern carriers. It is aimed primarily at the professional
archivist transferring them to conserve them, and it is generally assumed that the purpose
is TO PRESERVE THE ORIGINAL SOUND. (That is what I understand to be the function of
a “National Sound Archive”, rather than preservation of the artefacts; that would be the
function of a “Museum.” Please feel free to disagree with me, though!)
Here is one disagreement I myself accept. In many cases the work of people
behind the scenes is just as important as that of the performer, for example in editing
defective sections of a performance; so this must often be modified to read “to preserve
the original intended sound.” I would enlarge this in two ways. When it comes to the
subject matter, it must surely mean “intended by the producer of the recording” (or the
film or the broadcast), although this will become rather a subjective judgement. And
when it comes to technical matters, it must mean “Intended by the Sound Engineer.”
Hence this manual!
I also need to define the word “sound”. Do we mean a psychoacoustic sensation,
or objective variations in pressure at the ear(s)? In other words, when a tree fell in a
prehistoric forest before animals evolved ears, did it make a “sound” or not? In this
manual I use the second definition. It even seems possible that some form of genetic
engineering may enable us to develop better ears (and brains to perceive the results, plus
ways of storing and reproducing nerve pulses from the ears) in future. But the objective
nature of sound pressures is what a sound archivist can (and must) preserve at present.
The arrangement of the book is as follows. After two chapters on overall copying
strategy and the conversion of analogue sound to digital, we have five chapters on the
techniques for getting the sound accurately from various analogue media. Each has some
history and some scientific facts, and shows how we may use this knowledge to help us
get back to the original sound today. The section on setting playing speeds, for example,
covers both objective and subjective techniques, and contains a summary of our objective
knowledge for reference purposes.
Next come three chapters for special techniques to ensure an old recording is heard
the way the engineers originally intended. One deals with noise reduction systems, the
second where spatial effects occur (e.g. stereo), and the third where the original dynamic
range of a compressed recording might be recovered. These are all problems of
reproduction, rather than of recording.
There are vast areas where we do not have objective knowledge, and we must rely
upon future developments or discoveries. So I have left the discussion of acoustic
recording techniques until this point. (I define “acoustic recordings” as “sound recordings
made without the assistance of electronic amplification”). Besides our shortage of
objective knowledge, the whole subject is much more complicated, and we must use
previous vocabulary to express what little we know. Although large amounts of research
are under way as I write, I can only indicate what I consider to be an appropriate strategy
for a sound archive, which will give better fidelity for listeners until ideal technology
becomes available.
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