I can't track the source of this hum on my recording, help?

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Purebe

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Problem:

I have a consistent hum I can't get rid of. I've uploaded a .wav of it here: (nevermind... apparently I am not allowed to link to it.)

Setup:

Currently I'm plugging an M-Audio Fast Track USB 2.0 directly into my laptop's side-USB ports, running a custom-made XLR shielded cable with Neutrin endings to my behringer C1 condenser mic. It's sitting on a simple desk-stand and using a pop filter.

The USB cord from the FastTrack is at least 4 inches away from the XLR cable, and the only other cable nearby the XLR cable is an ethernet cord to run my internet to my laptop. Nearby the USB cord is my laptop charger, although, I've tried moving the USB cord ~2 feet away from that without any noticeable differences.

My roommates ~36"ish TV is sitting behind me (not much I can do about that) but it's off (still plugged in?) I tried moving it a few feet away more but I don't think it made any difference.

There is only one power-source for the entire rig, the laptop, which is plugged directly into an outlet but has a grounding plug (it's 3-pronged) so I'm not sure if that makes any difference.

Future Ideas

I currently do not have a power-strip or a powered USB hub. I've read these can help eliminate hum, and I'm looking to pick one of each up to see if it will help (if I plug the laptop charger and powered USB hub into the same power strip which is plugged into an outlet which is used by nothing else, then maybe that will fix it?)

Besides that, I think I'm out of ideas.

Also, it may just be my ears playing tricks on me, but if I concentrate really hard I can almost hear a faint hum at any given time. If that's the case, is there anything I can do to avoid the mic picking it up?

Sorry for the bombardment of questions, just not sure what to do at this point. Thanks for taking the time to read this!
 
Try running your laptop off its batteries - the power supply for it is most likely the culprit.
 
Hmm I don't think it was the power supply, I turned it off and waited a few minutes and tried - what resulted was no hum, so I thought it was working. Then I plugged it back in and no hum, so it turns out it was just environmental noise I guess? However, the background noise was still IMO too loud, but it didn't sound like a hum or a hiss and I couldn't hear anything otherwise, so I'm not sure if that's just the noise floor for my set up or if there's more I can do to fix it.

I'm starting to think I'm going to need a better audio interface so I can maybe gate out the background noise or something
 
Odd 'cause you're sort of going in two places there- the hum now gone(?) -or a case of maybe its not so abnormal (bad) comparing to good healthy signal levels?
 
mixsit said:
Odd 'cause you're sort of going in two places there- the hum now gone(?) -or a case of maybe its not so abnormal (bad) comparing to good healthy signal levels?
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I have no idea what's going on. I've been tweaking settings and reading as much as I can about how to get clean sound with minimal background noise (I just want it to not be distracting) and my set up sounds a lot better than it did originally, but, this is just confusing to me.

Earlier today I set up to record and there was a hum. I tried for a few hours to get rid of it, no luck. I posted here after my recording session - later after class I went to check the hum again, but it was gone and now instead there was just background noise (can't really describe it but it clearly wasn't a hum or a hiss.)

I'm guessing the hum was coming from the buildings walls, and it just stopped, and it was over-powering the other background noises. Unfortunately I am pretty lost at how to work on getting a cleaner audio at this point, filters make the vocals sound way too processed, which is frustrating because the background noise is really just only so barely too loud ><!
 
Get up to 10 post then post an audio sample of what your hearing for us.

You need 10 post to be able to link. ;)
 
There are a number of possibilities.

If the hum is intermittent, sometimes there and sometimes not, I would start looking at the vulnerable things first, i.e. the microphone cable. Have you tried another one?

Do you get the hum if nothing is plugged into the interface?

The background noise you referred to; is that just ambient noise from the room? Try turning the input level down.
 
gecko zzed said:
There are a number of possibilities.

If the hum is intermittent, sometimes there and sometimes not, I would start looking at the vulnerable things first, i.e. the microphone cable. Have you tried another one?

Do you get the hum if nothing is plugged into the interface?

The background noise you referred to; is that just ambient noise from the room? Try turning the input level down.
Click to expand...

I only have one XLR cable currently, hopefully it's not that. I'll buy another if I have to but cables are expensive :x

The hum has stayed gone, I'm starting to think it was just construction work somewhere or something.

As for the background noise, kind of frustrating. I can turn the gain down low enough that I can't hear it, but, then I'm far too quiet and when I boost things the noise is just reintroduced :x Is it possible to get a cheap hardware gate? Or maybe I need a mixer that comes with a gate built in or something, hmm
 
Purebe said:
..As for the background noise.. Is it possible to get a cheap hardware gate? ...
Click to expand...
No. Well yes you could gate it, but don't go there.
Noise like that, the solution is to get the source sounds higher in level at the mic,compared to the background bleeding in; I.e, closer to the mic, and/or louder at the source, and/or quiet the backgound, and/or put some baffles up to isolate you and the mic from it.
In this context a gate is last resort damage control.
Even then you would not do that while trying to record.
 
I've turned off the AC and the fridge which are the only things that are making noise in this room, there's other noises outside the room that I have no control over and unfortunately I don't have anywhere else to record at.

I'm unfamiliar with baffles, but it doesn't quite seem like they would be an option in this room because I don't have anywhere to put them. I'm looking at an image right now (argh not having 10 posts yet, otherwise I'd just link it) where someone lined a collapsible cloths hamper with acoustic foam and stuck the mic inside of that - maybe I can do something like that to reduce the noise. Any ideas in that regard?

I'm not sure if I can do much more regarding the input level of the mic, the gains about as high as I can get without clipping and it puts me between -24db and -12db sound volume by the noise is like -40~db, if I could drop the sound down to maybe -50db I think it wouldn't need any noise removal clean up.
 
Purebe said:
... someone lined a collapsible cloths hamper with acoustic foam and stuck the mic inside of that - maybe I can do something like that to reduce the noise. Any ideas in that regard?
Click to expand...

Do some searches for DIY and low cost sound baffles ideas- Some have done pvc tube or other hanging frames for heavy blankets, made fiberglass or rock wool panels, that sort of thing. (Rockwool/fiberglass and other soft stuff does the same as 'foam which is the 'looks good but expensive way to go.

I'm not sure if I can do much more regarding the input level of the mic, the gains about as high as I can get without clipping and it puts me between -24db and -12db sound volume by the noise is like -40~db, if I could drop the sound down to maybe -50db I think it wouldn't need any noise removal clean up.
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In this situation -source level vs background level- their relative loudness stays the same as you raise or lower your record level (or later your playback level.) So all you can do is whatever you can to make their difference better.
Recording fairly quite stuff in an open room can be tough.
 
KK, thanks - I'll look into a DIY solution. Hopefully this will let me lower the noise enough to get it acceptable!
 
One more question - is there any way to make the recorded audio sound as good, or at least close to as good, as the audio I get back when I go through direct monitor? Because, the direct monitor audio sounds _amazing_, especially compared to the recorded audio which just sounds bad in comparison. It doesn't really sound all that bad, but, compared to the direct monitor playback it does sound pretty bad.

Is that just to be expected? The m-audio fast track is set to stream at 48kz and 24 bit, if I record at 96khz in audacity I *think* it sounds better, but I'm not sure if that's just an illusion, I don't see how it could sound better if it's only getting a 48khz signal..

Any ideas?

edit: Also, it sounds a lot better on direct monitor even when someone else is talking, so hmmmmmmm
 
Purebe said:
edit: Also, it sounds a lot better on direct monitor even when someone else is talking, so hmmmmmmm
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Are you checking on headphones?
Often people think direct monitoring sounds better because you can hear the bleed from the live source as well as the direct sound in the headphones.

Direct monitoring should sound identical to recorded audio.
It's not identical, technically, but if you can hear the difference one pass of a/d d/a makes, fair play. ;)
 
I'm using YUIN PK-3 earbuds. It might just be the bleed, but man it sounds a lot better. Now I'll want to chase that sound quality forever :D

(I searched around and that's about all I could find on it, I wasn't sure if there was something I was doing wrong in recording it or something:x)
 
For tracking down periodic noises (as against hiss, white'ish noise) a spectrum analyser is invaluable....'K off you all say but you don't have to fork out for Audio Precision kit! Most DAW software has one in it somewhere, might be with meter options or in Tools.

If you really don't have one Samplitude Silver deff' does (and maybe Audacity?).

Inspecting thus look for 50/60 Hz. If present you have direct pickup of radiated mains hum. Earth loop hum will be 50/60Hz but with harmonics extending throughout the spectrum, usually past 3-4kHz.
100Hz or 120Hz and harmonics is "equipment" hum from a poorly smoothed power supply.

Frequencies not related to power supply, AC or DC will be fans, maybe hard drives.

"Squeaks" at kHz frequencies, showing as single spikes are shortcomings in the converters or a poor gain setup, especially happens with usb kit and Win7.

Dave.
 
I just recorded a bit of the background noise, here's a plot spectrum analysis of it in audacity:

https://i.imgur.com/y5vZg.png

Now my laptop fan was on and I know that was being picked up a bit, but it's running hot right now and I'm not sure why (I think I need to dust it out or something, GPU idling just under 80C isn't good :x)

Besides the laptop fan, there's still other noise.

Here is my attempt at reading it, if anyone wants to double check it I'd be very grateful: Both 50hz and 60hz are "spikes", so I should be concerned with mains hum then (which means I need to ground these differently or something? I'm not sure, because, the mic plugs into the fast track, the fast track into the usb, the laptop into the charger, the charger into a grounded outlet.)

The only "squeak" I see is at just under 1khz (843hz) and it's around 5db louder than the sound floor, probably not audible.

I clearly have the 100hz/120hz so I'm guessing this is my power supply. EDIT: I don't think it's the power supply, at least not for the laptop. I just unplugged it and put it on the other side of the room and it didn't make any difference on the sounds (I checked the plot spectrum as well, which looked nearly identical)

Then there's the 3hz to about 40hz, which I'm guessing is the laptop fan?

All the help so far is greatly appreciated, and any continuing help is of course awesome and very much appreciated as well! Thanks:D
 
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100hz/120hz makes me think of a power supply - maybe not your laptop, but something else that is plugged in? Something that has a full-wave rectifier (60hz ac to 120hz dc waveform - ie, doubles the mains frequency) could be the culprit. Are you in an apartment? Could it be someone else's electronics in a nearby room?

Flourescent lighs can also induce some noise, but I found this was mostly with guitar pickups and other EM based things. could affect a mic conceivably...
 
My roommate (6-7 feet behind me) has some DJ stuff..an S2, decent sized speakers, two computers, and there's a big ~36"ish TV sitting 1.5-3 feet behind me buut it's off.

He gets some kind of interference on his speakers, maybe there's something in the floors or the walls or something. And yeah, I live in a dorm room, so if that's the case I won't be able to directly do anything about that stuff.

Also, I do have fluorescent lights, but I have them turned off (I don't think I notice any difference with them on, but they are off just in case.)

Would a portable booth made with some acoustic foam or rock wool or something help out with this stuff? Maybe I could gate out frequencies under 300hz (I don't think that would affect voice work since it's such a low frequencies, or would it?)
 
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