Not unknown it seems.
https://www.researchgate.net/publication/229019522_Practical_investigation_into_EMI_from_a_lift_motor
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I live in a very noisy EMF environment, near both a cell tower and an electric train. I get all sorts of racket from the air, not from the power. Unbalanced cables are the entry point, as they act like antennae.
A simple test was recording with a battery powered Zoom recorder from a device with an unbalanced cable. That helped lay out the possibilities for addressing the racket. For me, it was abandoning gear that was susceptible, such as powered speakers that used unbalanced input cables.
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sadly my Active Crossovers for my Active speakers are all RCA in/out
You might come up with some experiments to identify if the noise is coming through the power or if it is EMF. Knowing that will keep you from wasting money on the wrong solutions. In my own situation, I could have thrown a fortune at the power without impacting the noise since it is coming from EMF.
After you’ve build Faraday cages around everything and you still hear the noise, perhaps it’s being beamed straight into your head. So you will need
ROFL
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I hear the same noise at all the apartments power meters in the whole block and other blocks nearby.
It could also be from inverters used on the roof solar for lighting in the common areas…first world problems 
Just wanted to chime in, the noise definitely comes from the hdb lifts , some of my equipments has been plagued by the on and off whining . When the lifts are stationary , it be dead quiet and when the lift starts to move the whining will start. After years I only been managed to get rid the noise out of my passive speakers by using a medical grade isolation transformer for the speaker ampflier . The noise will come through to all the power lines in the house while most of the common equipment won’t likely pick up the noise /emi but it will always be there sadly . So my take if the noise on the equipment is power induced ,a isolation transformer will help and if it’s emi/airbourne induced there’s no fix
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I think it’s the lifts also….but not had it recently at least my wife hasn’t said anything.