Researchers began to deal with noise reduction of musical recordings firstly in the 70's. The noise reduction subject came again into foreground when the Compact Disc appeared. CD is an excellent medium to archive musical data without quality loss. However, nobody wanted to copy directly noisy sounds to the disc. Usually a noise reduction procedure is needed in these cases.

In this article I deal with analogue and digital noise reduction techniques on gramophone recordings. First the history of gramophone will be shown. The second part talks about distortions on records. In the last two parts, some restoration methods will be discussed.

This essay is not a comprehensive scientific article. I just wanted to show some interesting things from the world of sound restoration and I tried to explain them in popular-science form.

Table of contents

1. Short history of sound-recording

2. Frequent distortion types in musical recordings

3. Physical and analogue noise reduction techniques

4. Digital noise reduction techniques

5. Bibliography

You can hear the results of a noise reduction algorithm on this 45 seconds long sound-part. The algorithm was developed by me. The first 10 seconds is the original noisy sound, then you can hear 10 seconds of cleaned sound, then 10 seconds noisy sound again and finally again cleaned sound.