How fortunate we are to have audio recording media such as quarter or half
inch analogue tape with Dolby SR noise reduction, DAT, 1630 and the various
other digital formats that are currently available. We can capture sound with
an almost incredible accuracy and, with due care and attention, be sure that
no intrusive background noises, other than an almost non-existent hiss, will
mar our listening pleasure. And with Compact Disc, this degree of perfection
extends right down the audio chain all the way to the domestic and even to in-car
and personal stereo users.
Things haven’t always been so good. Remember the days when your record
collection was your most prized possession? And remember how it felt when you
lent a disc to a friend and it came back with an ugly scratch all the way across
your favourite track? And do you remember how an old fashioned black disc could
be perfect one day, and the next time you played it the music could be almost
obliterated by a swarm of tiny but irritating clicks? I could go on to remember
the times I have spent in record shops complaining that the disc they sold me
wasn’t perfect, and received the answer, which could be phrased in one
of a thousand ways but always meant, “Well that’s just the way things
are and you’ll damn well have to learn to live with it”. These are
not happy memories.
The Holy Grail of the record collector, then and now, has always been a device
which could somehow magic away all the unwanted crackle and let you listen to
just the music. There have been plenty of attempts over the years to invent
such a device, but until very recently none has been successful enough to convince
critical listeners. Manual methods, such as copying onto tape and cutting out
the scratches, have had some success, but it is inevitably a very labour intensive
process and it can only deal with very major blemishes on records.
Over the last couple of years we have been hearing quite a lot about a •process
known as CEDAR which claims to remove clicks an d other non-musical events from
old recordings, and there has been some interesting discussion in Studio Sound
recently (May and July 1990) which I do not propose to elaborate on. I hope
in this article to describe what CEDAR is and what it does, and give a personal
impression on how well it performs. The precise details of how the process works
involve high flying mathematics which must wait for another day.