I used Hum remover at 1,1,100% setting and it sounds better but I’m not sure if that’s the right way and there’s still some hum left. I’m a novice. I can’t find a section where it’s just hum in the full audio.
If you look at the spectrum (https://manual.audacityteam.org/man/plot_spectrum.html) you will see that the hum is primarily at about 56 Hz (not the usual 50 or 60 Hz).
You try using the “Notch Filter” (https://manual.audacityteam.org/man/notch_filter.html) with settings of:
56 Hz, Q = 2
and again with:
29.5 Hz, Q = 4
Thanks, the notch filter works better than hum remover. Running a second notch filter at 29.5 Hz, Q = 4 doesn’t seem to make a difference so I’ll undo it. I’ve to teach myself how to read a plot spectrum.
To clearly see mains-hum & it’s harmonics on Audacity’s spectogram it’s necessary to change the spectrogram settings from the default values …
The constant horizontal lines on the spectrogram are hum & harmonics, which can be notched out.
If you’re in a country with 60Hz mains (e.g. USA), the 56Hz value could be due to the tape running slow.
If you speed up the digital recording of the tape in Audacity by 1.067 then you can de-hum 60Hz & harmonics …
Thanks Trebor. I have to teach myself how to read a spectogram.
Can you try another hum sample? https://www.sendspace.com/file/glqxhc
I wasn’t able to eliminate the hum completely using notch filter at 56Hz.
56Hz is the fundamental-frequency, there are also multiples thereof : harmonics.
Most of the hum is the harmonics …
You have another problem : the tape is not running at a constant speed , so the hum fundamental wobbles unpredictably every few seconds.
Ideally you need a de-hummer which will track the fundamental frequency, (because it’s not constant).
Thanks Trebor, that’s informative. The hard part is finding these harmonics.
If you increase the window-size (resolution) of the spectrogram settings to 8192,
the harmonics become visible as constant horizontal-lines …
[ * each notch adds a ringing artifact, so use the least number of notches to produce an acceptable result]