What Is Causing This Noise?

[soundchaser59]

I record my guitar cab with an SM7b. But tonight I noticed a strange noise in the phones, and I isolated it to the SM7b channel. Even if I turn the guitar amp off, I still hear this noise. There are no effects on, just SM7b into the (Emu 1616m pci) mic input, straight to Sonar. I put a Heil mic in front of the guitar speaker as a test and it did not pick up anything, so I know this noise is coming thru only on the SM7b channel. I have not done anything else to isolate it, but wonder if anybody has heard anything like this before?

If I sit there just listening, this noise happens roughly once every minute. The interval is not consistent, sometimes a minute, sometimes a bit longer, sometimes 30 seconds or so, etc....and it sounds slightly different every time it happens, sometimes shorter, sometimes a bit longer, usually just once but sometimes twice or three times in a few seconds, etc..... There are no motors or anything like that in the house. I have no idea. This just started tonight and last night.

http://www.soundchasermusic.net/demos/whatisit.mp3


Any ideas? It isn't very loud, but it does get recorded......

Almost sounds like a bug like a small moth trapped inside the SM7b capsule....

[Jim Lad]

Checked the reviews and not a bad one to be found.
Can you duplicate the sound?

[darrin_h2000]

Maybe there is somthing causing an impedance mismatch...cord maybe?

[dgatwood]

I suspect it's a variation of GSM chirp. For some reason, the frequency component is getting damped and you're just getting the switching pop. This is an artifact of GSM cellular phones and the way they switch on and off their transmitter at a particular frequency while identifying themselves to the tower and while sending and receiving data (but not voice, oddly enough).

Try taking your cell phone out of the room when you record and see if the problem goes away.

[soundchaser59]

the person with the cell phone will be gone all day today. Be interessting to see if the noise returns when she does!

[Manslick]

Yep it's a cell phone. When my brother is in my truck I can tell when he's about to get a call because that exact same sound comes thru the radio.

[ralpheo]

That's funny, because I have the 1616 pci into a pcmcia adapter. I have my phone on in my studio all the time and I never get that interference. Check your xlr cable. Try the amp again with the Heil in front of it when you know shes on the phone. I don't think it's going to be exclusive to the Shure. Good Luck.