Ringing/Feedback Sounds

[Rizzo39]

I'm currently using an sE2200a2c condenser mic, attached to a Scarlet2i2 Focusrite 2x2 pre-amp. My computer is an HP laptop running Windows 7. My version of Audacity is 2.0.1. I'm recording a Mono channel at 48000 Hz, 24-bit.

As you can hear from the attached sample, there is a light ringing sound whenever the mic experiences a slight vibration, either movement or just my voice. It's slight, but it is enough to be heard. Because it isn't a constant sound, I have been unsuccessful in removing it with Noise Removal, and while I'm sure there is an editing component that could get rid of it, I'd rather it just not exist in the first place.

I have replaced the mic once already, used it in various parts of the room, used it on and off the mic stand. My input and output in Audacity are both set to the Scarlet Line and I have recorded with the volume on the Output on mute and full volume. The gain setting on the Scarlet is relatively soft (I had to Normalize the attached clip to make it audible). I don't use headphones when I record, so there's nothing else attached to the Scarlet but the mic and the cord to the computer.

I'm very new to audio, so there may be a simple explanation I have yet to try, but I'm at my wits end. Many thanks in advance for help!

[kozikowski]

Oh, that's good. I would have guessed feedback, but if you're wearing headphones...

I'd rather it just not exist in the first place.

So would we. Nothing quite like the posting that starts: "Can you help me clean up..."
No, probably not.

Just to cover the bases, it happens after you restart the machine and you turned off Windows Enhanced Services?

I need to dig through your equipment list and listen to it again.

It happens if you turn your headphones off, completely off? What happens if you tap the microphone with a pencil or tap two pencils together? I've designed my own microphone amplifiers and it sounds on first pass like your microphone amplifier is oscillating - singing -- or just about to and anything at all can set it off. This isn't unusual. A microphone amplifier has to be able to make a microscopically small signal (hence the name "micro-phone") 1000 times or more bigger. To put this in perspective, that's the difference between a flashlight battery and the high tension power lines that power your neighborhood.

As we go.

Koz

[kozikowski]

So reading this carefully this time, you don't use headphones at all when you perform.

It seems that everything is standing on the USB connection. Is that what you're using for the show sound, or are you using the analog outputs behind the Focusrite?

The Focusrite gets its operating voltages (5 volts) from the USB connection at the laptop. The microphone gets its 48v Phantom Power from the Focusrite. That's not a contradiction. There are chipsets that can easily get between any voltage and almost any other. They are welcome. Microphone technology was just starting to fragment into different Phantom voltages when that happened. We hope those oddball, non-48v, microphones never see light of day.

Is there any chance at all you can plug the whole shootin' match into a different computer? Change the USB socket on your computer?

I'm on the edge of my seat for your posting of the pencil tests.

Here's one. Can you make it worse? Is there anything you can do to make the problem awful?

Where did you get your XLR cable from?

http://kozco.com/tech/audacity/pix/XLR-Cable.jpg

Are you using a cable exactly like this, or are you going through adapters with cables you happened to have lying around. I'm concerned that in addition to your ringing sound, there's also some power line buzz down there. I would not expect that in your system. So you may have two problems.

Koz

[kozikowski]

Most of it is oscillating at 3911Hz, highly audible, so the desperation method is a sharp suck-out filter (technical term) at that frequency.

Effect > Notch Filter: 3911Hz, Q=10

There's still problems down there, but they're much less audible.

Koz

[kozikowski]

I'm generating increasingly exotic symptoms. If I amplify the ringing sounds in your clip, they also have, in addition to the tinkly bell sound, thumps and bumps very much like, (drum roll) a very unstable microphone amplifier.

I would go to great length to plug the Focusrite into a different computer.

Koz

[steve]

It's going to be difficult to tell where that whistling is coming from, whether it is the microphone, the pre-amp, or the computer, unless you are able to test each component separately.
To filter out the whistle you can use this code in the Nyquist Prompt effect:

Code: Select all

(notch2 (notch2 s 7800 40) 3905 30)

[kozikowski]

It's the second microphone and when the poster tries a different computer, that points to the Focusrite -- assuming the problem doesn't go away. If the problem does go away, then the USB on the laptop isn't up to the task.

In that case, a single task, wall-powered hub may be the answer.

Where did you get 3905 from?

Koz

[steve]

Where did you get 3905 from?

It's a compromise.
Looking at the Spectrum exported data with a larger FFT size you can see that there are a couple of peaks:

3880.371094 -53.265541
3881.835938 -50.811146
3883.300781 -41.670887
3884.765625 -39.183887
3886.230469 -34.724258
3887.695312 -28.841604
3889.160156 -27.419273
3890.625000 -27.952753
3892.089844 -28.399023
3893.554688 -31.914761
3895.019531 -34.382568
3896.484375 -37.178196
3897.949219 -41.699516
3899.414062 -52.944550
3900.878906 -50.743919
3902.343750 -40.188969
3903.808594 -36.856556
3905.273438 -33.753937
3906.738281 -31.134001
3908.203125 -28.045319
3909.667969 -28.275234
3911.132812 -27.053244
3912.597656 -29.510462
3914.062500 -35.103012
3915.527344 -39.407402
3916.992188 -42.489494
3918.457031 -50.399410
3919.921875 -52.053349
3921.386719 -49.168476
3922.851562 -49.215923
3924.316406 -51.962391
3925.781250 -51.894985

That's not actually how I got the figure. I tried your 3901 Hz figure, then made the notch narrower and it left a sliver of a spike on the right hand edge of the notch. Shifting the centre frequency just a little to the right (a few Hz higher) was enough to catch both peaks.

[kozikowski]

My guess was 3911, not 3901. That's one of the answers that Analyze > Plot Spectrum gave me, and yes, I suspected that there were multiple peaks from the odd behavior of the cursor.

So I just launched the Plot Spectrum Magnifier Tool and ..... Oh, wait. Plot Spectrum doesn't have a magnifier tool.

Darn.

Koz

[Rizzo39]

I've just gone cross-eyed with all the tech jargon, but I will attempt to answer the questions. (And thank you for asking!)

- I have yet to try another computer, I'm workin' on that. I have plugged it into all of my USB ports on this computer, though (some of them don't even work, but I think that's an HP issue). Same problem with all working ports.
- I have one XLR cable, a Blue 20' Premium Quad Cable
- I have restarted the machine, but I'm not familiar with "Windows Enhanced Services." Please explain?
- My XLR cable plugs into the front of the Focusrite, the USB cable comes from the back and plugs directly into my laptop.

I don't know what all the number talk means, but I guess the takeaway is that I'll try another computer and circle back with you when I know more. Unless you think that this "Enhanced Services" thing is a solution. Thanks!!!