I’m working on editing some oral histories I’ve recorded in the homes of several neighbors. I’ve tried using noise reduction and noise gate to reduce some particularly annoying background hum but the voice ends up sounding very distorted. I’ve tried adjusting the settings in both but am about to just give up. Any suggestions? My deadline is fast approaching!
UPDATE: Uploaded an audio sample
MOL Sample -bad humming.aup3 (1.8 MB)
For power line hum, try a high-pass filter around 100Hz. “Whine” is more difficult.
Regular noise reduction and noise gating can be “worse than the disease” when the noise is bad… They work best when you don’t really need them. 
There is a new AI Noise Suppression Effect
which I haven’t tried.
If there’s video and the audio is bad, subtitles are often the best solution.
…There’s a reason that pros still record in soundproof studios with good equipment and good mic location, etc. 
Noise is pretty-much the last remaining problem. You can get good mic and a good audio interface for a couple-hundred dollars but soundproofing is construction.
I was going to ask if it is a “high” hum, or a “low” hum, but now that I think about it, you would do best to extract a few seconds of it and post that here, where the experts can give you an analysis.
Thanks- I added a sample to my original post. I can try to make it longer — had to shorten it due to size restricitons of the upload.
If you’re trying to do this yourself, I suppose the answers you’ve received are helpful. But I come across this frequently with interviews or street sound recordings or very old recordings and for anything important I just send it to my very experienced engineer; he’s got plugins I’ll never bother buying and I’ve found that since the objectionable sounds in an interview are often present in the entire recording the engineer gets to the heart of the problem in 15 minutes. I’m also a recording engineer and put down tracks of my own, but my expertise can’t compare to someone who does this every day of their lives and is up to date on all the latest miracle plugins. Good luck.
Applying a lot of graphic EQ at 1.0kHz and 1.25kHz, as shown below, greatly reduces the audibility of the noise. This is equivalent to a deep notch filter. Of course, the notch filters suggested by @Trebor are a much better approach.
Zooming in on the frequency axis of the spectrogram, we can get a better idea of the three noise-making frequencies in question:
Thank you for the suggestions. @Trebor I’m pretty new to all this “sound engineering” stuff so please excuse my ignorance here. The entire recording is about 45 minutes and the hums are consistent throughout it. Is the notch filter suggestion here something I can “select all” and have it repaired all at once?
“select all” option is to select the entire duration of the audio, not just part of it. IMO you need 3 notches
BTW if the pitch of the hum changes over the 45 minutes the notches will become less effective at times, (Audacity notches do not track the hum frequency).
Trebor:
Can you make an animation of how to run the Plot Spectrum tool to find the exact frequencies of those peaks for the Notch filter?
It’s a lot easier using the spectrogram display and Audacity’s spectral editing tools
The spectral editing tool works really well. @Trebor, thank you for the detailed description of how to use it. I performed a frequency analysis of the lead-in waveform after three notch filters were applied. Their effect is clearly visible, with the amplitudes of the three noise peaks being significantly reduced.
I totally understand your struggle—background hum can be a nightmare, especially when it’s mixed with natural room tone. One trick I’ve found useful is using gentle notch filters instead of aggressive noise gates or reduction. It preserves voice quality better. Also, try using a spectral denoise tool (like in iZotope RX if available)—it’s a lifesaver! Would love to check out your sample and see if I can help more specifically.
Thank you to everyone who has offered solutions. I have to admit they all seem a bit intimidating to me. That said, I have learned a lot that I thought was intimidating in the past and am willing to try. Thankfully, most of my recordings are not nearly as bad as the one sampled in my original post and, aside from this and a couple others, I am making good progress. Thank you again and any less intimaidating suggestions are much appreciated if anyone has one!
Upload to an AI noise reduction service, e.g.
(A short sample is free, not 45 minutes) .
before-after
OMG! That’s an amazing difference!!! Trying it now!!!
well daggoneit- it won’t let me do it more than once without paying for it… I don’t mind paying a little… but if I’m going to pay for one- any suggestions on which one and/or might there be more free options? I’ll definitely be Googling answers but thought Id throw it out here too.
If you’re on Windows, the free OpenVino AI plugins can work in Audacity …
