The Mudcat Café TM
Thread #155388   Message #3656548
Posted By: GUEST,CJB
03-Sep-14 - 12:42 PM
Thread Name: Tech: Removing hum from old tapes
Subject: RE: Tech: Removing hum from old tapes
Thanks for all of your advice. Here is what I did:

From a totally un-listenable reel-reel tape (50 years old) copied to a cassette tape - this latter was recently digitised. The hum actually came from the dubbing onto the cassette. The reel-reel tapes are long out-of-reach. But the hum was so noisy that the music could hardly be heard. However a combination of Reefer (using ReaFIR) and then Noise Removal on Audacity - and the result isn't bad. Some links:

Basically I had a WAV file from the cassette tape. This I read into Reefer. Found a gap in the recording where the hum only was present - actually the gap created by the cassette turnover event. Using Reafir I created a noise profile and applied that to the recording. I saved the result as a FLAC file.

I wanted to repeat this for the residual hum. But Reefer was producing a crackling sound when I re-opened and tried to play the FLAC file - so I abandoned that idea.

I then read the FLAC file into Audacity. I applied Normalisation, Pop Removal, and a speed decrease of 2% (Reefer didn't seem to allow for these).

Then I found the same gap with the hum and copied this into a new file with Audacity. Then I scanned that with the (Nyquist) Noise Removal effect. Then I applied that new profile to the whole file.

Finally I saved the result as WAV. FLAC and MP3 (320 kbps).

It is the latter which is uploaded here:

London Folk Song Cellar programme 10 (of 39).

LFSC 10 - TD 115636.37 - RMcL c4 (320)


P.S. I will also give SoundSoap a try later.