Topic: Please have a listen to this annoying noise...

[yousef]

We taped a session by a lovely folk singer on Sunday but seem to have picked up a rather annoying artefact along the way. I'd appreciate it if you could have a listen to the sample and let me know if you have any ideas about how best to reduce its impact.

We recorded using three tracks of a Fostex VF160: vocal via SM57, and the nylon strung guitar was mic'd with two cheap Behringer C2's powered by the Fostex's own phantom.

What I'm hearing is a constant sort of "electrical" fluttery noise. It is only present on the guitar tracks and is only present when the guitar is actually playing. Cheap mics? Cheap preamps? A combination of the two?

The question really is what to do with it. Because it's only present when the guitar plays I don't see a way for traditional noise reduction software to sample and reduce it. I could post one of the guitar tracks in isolation if that helps but there's a lot of bleed from the vocal onto them anyway.

11MB FLAC:

http://www.sendspace.com/file/2et40b

[runonce]

I cant hear anything wrong...certainly nothing fluttery...or constant.

Something happening on your monitoring system?

[yousef]

Interesting...

I've listened to the unmixed tracks in Vegas and the mixed stereo track in WMP both through a firewire soundcard and my laptop's internal sound and thought I could hear it throughout. I did think it was less obvious when listening to the recording on the Fostex though... I'll have to experiment further.

Thanks.

[fmaderjr]

Sounds great on my computer too.

[yousef]

I wonder if it's my headphones. Or maybe I've just become fixated on the noise and am amplifying it in my head...

Thanks for the input - an extra few pairs of ears always goes a long way.

[anr]

There is a whopping great peak at 188Hz from the guitar. As soon as you start to reduce it, the vocal jumps out.   That slight tweak makes it far easier to listen to.  As it stands, it is very jarring, which is probably what you're hearing. 


http://www.sendspace.com/file/jc3bj9

[yousef]

I think the noise I'm hearing is above 188Hz but I agree that the bass could do with taming a bit too.

If you listen again to the original file and whack the volume right up you hear the room noise up to the 10sec mark when the guitar comes in accompanied by this mystery noise - which almost sounds like a metallic vibration to me, as if there was some loose foil over the speaker. If that makes sense.

[alpine85]

It sounds good to me too, but I also have a couple loud hard drives and fans going at the moment.

I did notice something kind of weird in the waveform, when I zoomed in on the silent parts, right before she starts playing (around the 7-10 second mark) and right after she stops (last few seconds of the file)

There's something going on way down in the noise floor area, and it seems to cycle at almost exactly 0.75 seconds.  Maybe that's the flutter you're hearing?   I have NO idea what it could possibly be, but I've attached 2 screencaps, with these areas selected ( you will see the peaks and that they are exactly spaced).    It doesn't seem like it's a 60Hz hum.  Maybe if you could figure out the frequency you could run a notch EQ on it, or if it's below 20Hz try a HPF. 

[yousef]

Very interesting...

Thanks for looking so closely and posting the screenshots.  I'm now thinking that this is something to do with the ageing and/or cheap preamps in the Fostex. Especially as the artefact you've identified seems to be present throughout but more obvious when the channel was handling a louder signal.

I'll have to try to recreate the setup but use an alternative p48 supply and preamp and see what happens.

Thanks again.

[alpine85]

Very interesting...

Thanks for looking so closely and posting the screenshots.  I'm now thinking that this is something to do with the ageing and/or cheap preamps in the Fostex. Especially as the artefact you've identified seems to be present throughout but more obvious when the channel was handling a louder signal.

I'll have to try to recreate the setup but use an alternative p48 supply and preamp and see what happens.

Thanks again.

No problem.  Good luck!  Let us know if you figure it out... i'm curious myself...

[andy_landy]

I heard the hard disc spin up regularly as it wrote data out.

0.75 seconds worth of 4 channels at 16/44.1 is about 256 kbytes.

256 kbytes is a nice round number and would make sense.

But I thought you recorded at 16/48?

(All assuming we left that 4th channel running, which I think we did)

edited to add:

ok so i looked at the user manual for the vf160, seems it only does 16/44.1, so that's probably it. it's unlikely to be the mics picking up the noise, rather it'd be more likely to be the internal electronics being upset by the relatively large current being drawn as the hdd spins up.

now, i don't hear any noise on my m10, which was hanging off the back of the fostex, but in fairness i've not been in a position to crank the level to a point where i could hear it (and neither have i been in an ideal listening environment). i wil get these files to you asap (but obviously they're already mixed down to stereo)

edited again to add:

fwiw back in the jb3 days, i recall some people complaining that their jb3's picked up hard disc noise. i was fortunate in that i had to add crazy amount of gain to make that noticable on my jb3. luck of the draw i guess.

[runonce]

I heard the hard disc spin up regularly as it wrote data out.

0.75 seconds worth of 4 channels at 16/44.1 is about 256 kbytes.

256 kbytes is a nice round number and would make sense.

But I thought you recorded at 16/48?

(All assuming we left that 4th channel running, which I think we did)

edited to add:

ok so i looked at the user manual for the vf160, seems it only does 16/44.1, so that's probably it. it's unlikely to be the mics picking up the noise, rather it'd be more likely to be the internal electronics being upset by the relatively large current being drawn as the hdd spins up.

now, i don't hear any noise on my m10, which was hanging off the back of the fostex, but in fairness i've not been in a position to crank the level to a point where i could hear it (and neither have i been in an ideal listening environment). i wil get these files to you asap (but obviously they're already mixed down to stereo)

edited again to add:

fwiw back in the jb3 days, i recall some people complaining that their jb3's picked up hard disc noise. i was fortunate in that i had to add crazy amount of gain to make that noticable on my jb3. luck of the draw i guess.

Perhaps - but that doesnt sound like what the OP heard.  Is it possible you're hearing your own HD read?

[yousef]

Perhaps - but that doesnt sound like what the OP heard.  Is it possible you're hearing your own HD read?

He was stood next to the machine while it was recording 

I think there are two issues here - the newly-discovered HD noise (which I hadn't noticed) and the more constant fluttery noise (which apparently only I can hear).

Between the two, I think there's an acceptable recording...

[andy_landy]

Perhaps - but that doesnt sound like what the OP heard.  Is it possible you're hearing your own HD read?

as yousef clarified, i was at the session. from a distance i heard a ticking noise, which on closer inspection was the hard disc doing its thing.

the waveforms that alpine85 pointed out appear to me to be hard disc activity that has interfered with the analog electronics of the fostex.

my sony m10 was plugged into the stereo out from the fostex. i've not had a chance to investigate whether this hard-disc activity has bled through to my m10, or is purely internal to the fostex.

i'm also not hearing the fluttery noise yousef is picking up on. although i've yet to listen back on anything resembling decent equipment...

s.