Technical notes index

Principles of audio noise reduction
Principles of audio noise reduction
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            CONTENTS

1. INTRODUCTION
      Distortion
      Frequency response
      Pitch errors
      Noise

2. FIXED PITCH NOISE

3. IMPULSIVE NOISE

4. RANDOM NOISE (HISS)

5. HISS REDUCTION
      Examples
      Companders

6. NOISE REDUCTION EXAMPLES
Finally, two complete noise-reduced 78s: each starts with the straight transfer and then after about 25 seconds changes to the decrackled and dehissed version. The decrackling was done first, care being taken not to overdo it and introduce distortion: then the same principles applied to the hiss as described on the previous pages.

Firstly, 'The ToyTown Party', from a forgotten musical show called 'Nippy' ( a 'Nippy' was a waitress in the Lyons Corner House tea-rooms): it's sung by Binnie Hale and was recorded on 27 November 1930: Columbia DB349. There is still some residual noise; but although it could have been further reduced, doing so removed the 'bite' from what is a very fine recording for its age. As always, a careful balance has to be drawn between reducing noise and retaining the quality of the original recording.


[hale_mix.mp3]

The second item is a modern vinyl pressing from the original master, so that there is no abrasive noise: the result shows just how good the original recording quality could be. It's 'Il était un roi de Thulé' from 'Faust' by Gonoud, sung by Conchita Supervia. It was recorded in 1932 by Odéon but originally unpublished: this copy was issued by The British Institute of Recorded Sound in the first issue of Historic Masters, on BIRS HMB11.


[supervia_mix.mp3]

These records were processed using ClickRepair and DeNoise.

You can download copies of these recordings with processing throughout by clicking on these links:  Hale | Supervia

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© Roger Wilmut.