high frequency intermittent noise

@kosst_amojan- is it possible that the building itself is set up with these devices you identified? (They seem to act like repeaters, to increase strength within buildings). Unless a neighbor set one up to improve his/her cell reception, as @jea48 alluded to, why wouldn't the building itself provide such a facility? Given the density and height of the buildings in Manhattan, I remember encountering dead spots in coverage walking around on the streets (granted, this was some years ago, I haven't done that for quite a while, and now no longer live or work in NY). 

@james1969 - alas, another quiet oasis in NYC gone to hell. 
This thread is fascinating to me for the deductive work- i know suffering the noise sucks--we've probably all had our share of imponderable issues at times- but i'm learning as i read this. 
The solution will probably be something obvious and stupid (e.g., did you plug it in?)
In the meantime, here's my tin foil hat conspiracy theory connect the dots, Elvis is an alien idea: if the subways have these critters, and the noise coincides with the passage of a subway under or near your building....?

Before you get all spendy on fancy audiophile cables* is there some pro level shielding material that you can buy to wrap the cables? I know that the shields typically go to ground on one end, but I gotta believe there’s a cheaper  DIY way to see if better shielding works rather than buying fancy cable.
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*I’m not a ’cable denier’ - I use high quality "audiophile" cable in my system, but I’d like you to solve your problem rather than just throw money at it. And cables can get spendy fast- whether they are synergistic with the sound of your system is a separate matter.

@james1969 - no, I was not. I was thinking of that braided stuff that is sold by electronic parts wholesalers or specialty suppliers, like the guy that sells the Duelund? cable that in certain cases needs shielding.

I reserve tin foil for hat lining, but make sure it covers the back of my neck. :)