high frequency intermittent noise

I have a noise issue that is intermittent. Here is what the noise sounds like:

https://clyp.it/4b233bmm

Here is what I know so far:

The sound affects all components and is compounded if all components are turned on. I have turned off my preamp, phono preamp, leaving just my mono blocks on, and the noise still appears.
I have turned off everything and unplugged everything in the house including my dimmer switch, and the noise still appears.
I have a pair of pro-audio monitors, self powered with class AB amps, and when I plug those into the same outlet, I hear the same noise coming through the pro-audio monitor. So this rules out my big system.
The noise is primarily during the day and goes into the evenings, weekends too, early mornings it does not appear.
I live in a pre-war mid-rise building. I have no ground, I'm using a Nordost QKore grounding system. This did reduce the noise floor quite a bit, but has no affect on this intermittent noise.
I have a cell phone tower directly across the street from my building in Manhattan.
Looking at a real time analyzer, I see peak at 2kHz when the noise appears.

james196911-12-2017 2:30am

shadorne Details Discussions Posts This discussion Message User 7,477 posts 11-20-2017 at 07:20pm Copy Comment URL Report Comment Edit Delete A choke is an inductor that chokes off high frequencies. The reason I think it is coming from the speakers and back into the Amp is because you have tried other steps. An very strong HF signal hitting the tweeter coil might also cause core saturation (hystersis) in the tweeter and this converts HF to broadband noise.
shadorne Details Discussions Posts This discussion Message User 7,477 posts 11-20-2017 at 05:14pm Copy Comment URL Report Comment Edit Delete This RF/EM signal must be picked up by the voice coil in the tweeter and it is likely a powerful megaHz signal and would be inaudible if it didnt cause problems for the amplifier(which tries to surpress distortion with negative feedback so as to match input) and the problem manifests itself in the audible range somehow due to signal saturation in the amp section making it a broadband signal. Try adding a choke across the speaker wires to short out the HF signal. http://audiosystemsgroup.com/RFI-Ham.pdf See Fig 4 for an example...