helicopters?

Could be a out of phase problem, that you cant really hear when you listen to speakers.
Could be a loop somewhere, maybe.

It sounds like the rotors of a helicopter going by your house hehe, that is the best way I can explain it. The recording is only one track from one source so how could it be out of phase? I have tried it from a bunch of sources too.

Do you live near Opus? You might be picking up the noise from the CPU Fan of his new 28Ghz P4

Nope Im in NY he's in Cali :-)

Did you look outside? LOL Just kidding.

It does sound like a loop. IF you take the headphone output and use that as the signal path to your amplifier and speakers and the problem still happens, at least you will know to start looking in the record /playback console in windows (if it is windows) or your mixer in the computer and uncheck some inputs and outputs until it goes away.

I hope this is helpful.

copter's in the 'puter.I never heard of that one yet, but I like it. In Sonar, try going to options>audio>advanced and see if you have the box checked that says "share drivers with other programs".