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....