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Gear / Technical Help => Post-Processing, Computer / Streaming / Internet Devices & Related Activity => Topic started by: acidjack on December 03, 2011, 12:04:25 AM
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Just recorded a solo acoustic show with many a technical problem. The main one - and probably the only one I can fix - is a very audible hum from the PA. This is pretty common at shows at this place, but normally the shows are louder, so it's less noticeable.
Any ideas? It's hum, not hiss.
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What were the instruments used? What is the lowest note sounded? In the US, hum is 60 Hz or multiples thereof and often the 120 Hz harmonic is greater than the fundamental. A steep HPF just below the lowest note played will clean up hum. For example, a guitar goes down to about 80 Hz so a 48 dB/octave HPF @ 80 Hz will get rid of quite a bit of 60 Hz hum. Sometimes I'll vary the HPF cutoff frequency within a song depending on what notes are being played. In that case I'll copy the track, HPF one @ 80 Hz and the other at maybe 150 Hz and cross fade between the two tracks as needed.
Most DAWs have a spectrum analyzer so it may be helpful to analyze the quiet part (i.e., nobody is playing) to see where the hum peaks are. If there are significant peaks at 180 Hz and above, you may have to use some notch filters to get rid of them since a simple HPF may cut out too much music.
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Try a Hum filter. I use Waves X-Hum but there are many. It is a relatively simple tool with 50 and 60Hz presets and well as DC Offset removal settings.
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It was just one guy and a guitar. Guitar had electronic pickup that was a little wacky, vocals were mic'd.
I'm using Audition. I tried some of the 60Hz filters it had and that did not seem to work. Just messing around with an EQ, it seems this hum - I guess really more of a buzz - is around the 8K range.
I'm trying the "Noise Reduction" feature now, but I'm assuming that will not actually work.
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OK, if the "hum" is actually an 8 kHz buzz, what I wrote about HPFs will not work. Try to run a spectrum analysis on the track to find out the buzz frequency. If the buzz is concentrated in a fairly narrow band a notch filter will help. If the buzz has a wider spectrum then a LPF may be in order.
DAW Noise Reduction features can help but don't try to push them too far. That is, don't try to get too much noise reduction or you will cut out too much music.
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