Session	Restoration of Smooth Pitch Variations Over Long Timescales - "Wow"
Presenter	Gordon Reid Cedar Audio, United Kingdom
Abstract .. ..Download Powerpoint Presentation .. ..Speaker Bio

ABSTRACT

You can encounter smooth pitch variation over long timescales ("wow") on almost any analogue recording medium, and it is one of the most disturbing artifacts encountered when listening to old and/or badly transcribed recordings. There are several mechanisms by which this can occur. One is a variation of the rotation speed of the medium during recording or playback. A second, specific to discs, is eccentricity in the playback process. A third occurs when magnetic tape stretches unevenly during playback or storage.

In some cases it is possible to make mechanical corrections for these defects, but such approaches are generally impractical. Therefore, this paper outlines a signal processing approach for the detection and correction of wow, in which we use the degraded audio to estimate the instantaneous amount of pitch variation, and then recreate the undamaged signal from the existing data. The approach used is as general as possible in order to correct a wide range of related defects.

SPEAKER BIO

Gordon Reid was educated at Leicester University and Cambridge University, UK, winning a Faculty Prize in 1980, and gaining a 1st Class Honours Degree in Physics and Astrophysics in 1981. An active musician and author, he became the founder employee of CEDAR Audio Ltd in 1989, and the company’s Managing Director in 1994. He is a member of the AES and over the past twelve years has presented papers and workshops ranging from the background and techniques of audio restoration to the history and uses of keyboard synthesizers. He has had more than 200 articles published worldwide, and his series of sixty-three essays entitled Synth Secrets is used as an educational text for music technology courses in the UK.