Removing mains hum

I just wanted to say thank you again for helping me with my original inquiry.

So I submitted the audio files for the church and we received contact back sating that their was a 60 cycle hum it appeared and that “noise reduction seems to be had used as voices cut into silence”

So I have two inquiries today.

First off, from what I read online you remove the 60 cycle hums via noise reduction ( ironic considering what was said about the audio… ) Is there anyway besides noise reduction to correct this? Suggested thing to do?

Secondly, How would I go about stopping silence with voice cuts off. Maybe it’s just me but if there isn’t a slight hum from the AC or something it would be silence? We don’t have music playing in the background or anything.

Hum is often best removed by filtering (assuming that you are not able to prevent the hum in the first place).

If you post a short sample of unprocessed recording, in WAV format, including a couple of seconds of “silence” (noise/hum only) and a couple of seconds of speech (or whatever the “normal audio” of your recording is), then we can have a look/listen and suggest specific ways to filter.

Hi Steve,

here is the unprocessed audio sample you mentioned I could attach. I wasn’t told by the radio station didn’t give specific times so I assumed it was a consistent problem.

Edit:t forum attachment isn’t allowing me to attach it for whatever reason I have uploaded it to my mediafire. It is only like 40-45 second sample.

If you could post a 10 second sample of silence (have the microphone on and recording volume set to normal level) I can analyze the file. 60Hz hum is rarely just at 60Hz - it includes numerous harmonics.

One approach I use, that gives a 3-4dB reduction in base noise, as well as completely eliminating 60Hz based hum is an isolation transformer. Hammond makes them. You plug it into the 120 or 240 volt mains and plug your equipment into it. Simple.

Try this plug-in:
Instructions for installing:

Try it with settings of:

  • 60 (Hz)
  • 8
  • 1
  • 1

An isolation transformer may indeed help, but they’re not cheap.
You could also try the cheap option of plugging into a different socket. Avoid having different bits of your audio kit plugged into different wall sockets - so long as you don’t overload the max power rating of the socket, it’s usually better (for reduced hum) to power all of the audio equipment from a single power strip.

A noise-gate, rather than noise reduction, has been used : that squelches the signal from the mic to silence when volume drops below a threshold.
[ In your example incorrect settings on the gate are causing the very start of some words to be cut off ].
Because of the reverb in the room, using a noise-gate sounds unnatural. IMO you should turn it off.

In your example you could get away with adding artificial reverb to fill in the silences created by the gate …

Hello all,

Once again thank you for all the comments and assistance. I have been in contact with the radio station program manager who was kind enough to as well review the original audio to help determine if it was on my side or on the church hardware/audio recording software side.

It does appear they are using a noise gate of some kind from what was observed from the original. I have advised the pastor to as well remove the noise gate.

Is there anything else you would suggest? How about for the hum issue? Or can that still just be monitored and filtered via Audacity?

Ideally find the source of the mains-hum and eliminate it, rather than remove it afterwards in Audacity.
Steve’s hum-remover plugin will get rid of the mains-hum. The notch-filters used in hum-removal add an artifact called ringing, but given the amount of reverberation from the room, no-one will notice the ringing.

Hello all just an update,

I wanted to thank everyone who has helped and provided usch top notch quality support. You guys are amazing and full respect.

Unfortunately at this time the church isn’t wanting to progress due to finances/how much it would cost to really fix the hardware issue so I guess my little project for them has been put on the side burner.

This topic can be locked now or whatever protocol is. :slight_smile:

Thanks again everyone!