Hi all. First time/hopefully only time poster here.
I’ve been using Audacity for well over a year now, and it’s time I finally get rid of this stupid problem. I’ve been recording a lot more stuff lately, and this is starting to drive me crazy.
I’m not an audio engineer, so I don’t know everything there is to know. Consider me an educated amateur, since I can probably tell you what 95% of the effects are and do in the menus, how to mix properly (although I’m usually too lazy to do so), work with my equipment, etc. But this buzz is really starting to drag on me, and I’m tearing my hair out on a solo guitar/voice piece that’s really quiet.
Attached is a recording. I’ve tried noise removal - only kind of works. I’ve tried a few Nyquist prompts, but they apply this obnoxious chorusey/reverb sound to my guitar that I don’t want. I’ve tried filters, but, again, no dice.
If you could give any sort of recommendation on where to go next, I’d greatly appreciate it.
The buzz is a classic example of “mains hum”.
I would guess that you are in North America as the hum is made up of 60 Hz + multiples (harmonics) of 60 Hz.
As you can see, those spikes in the spectrum (the buzz) go up from 60 Hz to over 3000 Hz. Because these frequencies cover much of the normal audio range, attempting to remove them from a recording will certainly cause much degrading of the audio that you want to keep.
The only solution is to fix the cause of the hum.
You will need to try and narrow down where the problem is.
Please describe your exact setup. What equipment are you using and how is it all connected together?
One thing that I notice is that the buzz is exactly the same in both left and right channels, so that rules out a lot of possibilities.
If there are only a few noticeable harmonics, then yes, with patience you could notch them all out without too much damage, but in this sample you would need to notch out about 60 harmonics, right across the all-important mid-range frequencies.
We can’t have this both ways. If the posted hum sample is typical as you said, then the Notch Filter page needs to carry a warning about the amount of work involved to notch and the risks of damage.
Extending this, could there be a Notch Filter where you can have multiple text boxes or enter a string of frequencies in one text box, then the effect does multiple passes at each requested notch frequency?
Yes, I am in NA. I knew about the 6ohz hum, hence why I was using Nyquist programming to try to rid myself of the hum. Here is the code I was using:
(setq a 15)
(setq v 20)
(setq freq 60)
(setq que (/ 10000 (* a a)))
(setq anti (/ 10000 (* v v)))
(setq mysound s)
(setq r sound-srate)
(setq iter (truncate (/ (/ r freq) 2)))
(setq d (/ iter anti))
(dotimes (i iter mysound)
(setf mysound (notch2 mysound (* freq (1+ i)) (* que (1+ (/ i d))))))
It damages the audio, though, giving it the weird effect I described above.
The setup I’m using is thus (down to the most exact details I can find):
-HP Laptop (dv6)
-MXL V63M Condenser Microphone on stand (4-5 feet away from any source of noise)
-Microphone cable (no idea the brand, but it was $20-$30 US dollars, so it’s not the cheapest of the cheap)
-ART Tube Amp Studio preamplifier
-Output to USB cable (again, about same cost)
Laptop is plugged directly into the wall (against my better judgement) and the preamp is in a surge protector on a different outlet. The surge protector isn’t the problem, either - it’s buzzed when I’ve recorded elsewhere without it.
I have one light in my room, but it has buzzed with it off. There’s no ventilation to make the noise. I have all my other electronics unplugged but what I’m using.
Last week I recorded electric guitar with a DI box, and, if I recall correctly, there was a slight buzz - it was mostly unnoticeable, though. This leads me to assume that it’s the microphone itself being the biggest offender, but I’m not sure.
As with any kind of noise reduction, how effective the repair can be depends on the severity of the noise - assuming that Gutei has not exaggerated the problem by recording the buzz louder than it really is in a normal recording, then that is quite a severe buzz.
Don’t we already say that it is better to fix noise at source rather than in post? If not, we should.
We already have an experimental plugin that does that (https://forum.audacityteam.org/t/hum-removal-plug-in/13561/1). The main drawback is that all such effects have been hampered by the lack of real-time preview (or any kind of preview until very recently) which makes it very difficult to find the right settings that do more good than harm.
Do you have a multi-socket extension (power) cable?
If you do, plug the extension cable into the surge protector, then plug both the laptop and the preamp into the extension cable.
Does that reduce the amount of hum?
Also, try recording with the pre-amp at its normal recording settings, but without the microphone or microphone cable connected.
Better or worse?
It’s looking like the preamp is the source of the problem. As far as I know, ART doesn’t have a bad reputation. But, it is more expensive to build a good amp or preamp with 1950s technology (tubes) than with modern solid state electronics.
It wouldn’t hurt to try a notch filter at 60Hz, and then at 120Hz. I believe the lowest note on a standard-tuned guitar is about 80Hz, so you could try an 80Hz high-pass filter (or maybe even 100Hz). But high-pass & low-pass filters aren’t “perfect” and an 80Hz high-pass filter will let some 60Hz signal through (depending on the sharpness of the filter). Notch filters aren’t perfect either, but you can get a TON of rejection at the notch frequency.
Since you have a digital connection to the laptop, the laptop shouldn’t be a problem. Hum (and noise in general) is an analog problem.[/quote] There is some potential for a ground-loop (causing hum in the analog electronics) with the laptop AC powered, but it seems like you’ve ruled that out by switching around the power connections.
If you are a guitar player, you probably know they are prone to hum/buzz. (It’s the nature of the high-impedance pick-up and high-impedance amp-input to pick-up AC signals from the environment.) A guitar amp will often hum (even with nothing plugged-in), although you might not notice 'till you stick a mic (or your ear) in front of the cabinet. A high-pass, or notch filter, or a noisegate, might help with that, but both of these have potential side-effects. A noisegate can make the attack unnatural and it will tend to chop-off the final-tail of the sustain. Probably the biggest help is to drown-out the hum with the guitar and the other instruments/vocals and fade-out the guitar when it’s not playing (like a “manual” noisegate).
Before we go off in all directions, it’s still very desirable to fix it at the analog stage. I have high tension lines over the house (attached) and I have microphones that pick up hum and buzz out of thin air with no sound at all, strictly through electrical radiation (as near as I can tell).
This problem responds to changing the position of the mic through the compass points. Turn it roughly south-west and the hum almost vanishes. That’s an easy test. Plug the headphones into the preamp and turn everything up. Wave the mic around and listen for changes.
Plugging audio into different wall outlets is a bad idea for audio. The protective shield and outer coverings of most electronics is connected to the third, round pin in a power plug (in the US). Depending on your house, the wiring in different sockets may be very slightly different. Any voltage difference can show up in the show (extreme example clip).
It’s the nature of the high-impedance pick-up and high-impedance amp-input to pick-up AC signals from the environment.It’s the nature of the high-impedance pick-up and high-impedance amp-input to pick-up AC signals from the environment.
Unbalanced ones. A primary cause of this problem isn’t so much the impedance as having everything on the stage unbalanced.
There’s three pins on the microphone socket, but only two conductors on the plug that goes into the amp. This cable intentionally mis-wires the built-in hum rejection of the microphone for the convenience and low cost of the amp. The down side of those tricks is the relative ease that you can get microphone hum, plus an amp and microphone connected directly to the wall socket.
“Koz? Can you come by with your meters? The bass guitar is getting lip shocks from his microphone.”
For a better recording of the end product, here’s a recording I finished the day after posting. It’s quieter than most of my other recordings since I had to keep the inputs low due to the worse buzzing.
You can notice how the noise removal/Nyquist made it a slightly audible hiss instead of a buzz and makes the audio slightly fuzzy. I’m hoping it was just a temporary thing, since it is always present but normally not nearly this prevalent.
Quiet hiss is always there in every microphone system. The object is to record with your voice loud enough to overpower it. If recording loud gives you the hum problem, then it’s possible you may never get there. Post Production patches and rescue filters always sound funny.
A while ago I did a voice test just to see if I could make it work. I discovered a hum problem of my own, but with almost no work and a very minimum of filter help, I pushed out an ACX compliant voice clip. If I figure out where my hum is coming from, I could almost do it with no effects. Just volume changes, because live recording standards and ACX are slightly different.
So yes, it can be done. This is not impossible. But not every house is a recording studio. If your room is actively fighting you, then the basic technique may have to change. We have a current poster who gave up recording on the computer and now records in a comfortable, quiet room with a portable sound recorder. She, too, can nearly produce an audiobook with almost no technical help.