The Swezey Digital Filter
Auto Equalization of Acoustical Phonograph Recordings
Crackle, clicks and pops are not the only problem in restoring early phonograph recordings.
Prior to the mid-1920's phonograph recordings were made mechanically without the use of any electronics.
One of the short comings of this method was that frequency response was not even across all frequencies.
Some frequencies would resonate in the equipment boosting them while others were dampened.
For example if you were recording a 1000 Hz tone and a 3000 Hz tone that were of equal volume one might
record louder than the other and so seem louder on playback.
This unevenness is why so many early recordings sound like they were recorded inside a box.
This technique can also useful to restore old and faded tapes.
To correct for this I have developed an algorithm in the program that adaptively tries to
estimate what the original response should have been and correct for it.
Below is a brief excerpt from Victor Record 19068-A
Yes! We have No Bananas
with Billy Murarry, The Great White Way Orchestra.
To hear (or download) the unequalized "before" version
Click Here!
To hear (or download) the auto equalized "after" version
Click Here!
Below is a brief excerpt from a homemade cassette recording of
Hello Dolly
as played by the Edison High School Band in 1970.
To hear (or download) the unequalized "before" version
Click Here!
To hear (or download) the auto equalized "after" version
Click Here!
All of these excerpts are MPEG mp3 audio files. If you need help playing these files
Click Here!
Thank you for your interest in the Swezey Digital Filter Program!
To return to the Phonograph page
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(c) 2007, Thomas F. Swezey. All rights reserved.