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Comment by compactmani | Hacker News Reader

I just left a 3 story walk up with central air and I can say the during the summer the large roof mounted AC units (technically split systems as you describe them) drove me absolutely insane. The humming caused by multiple machines running made it almost impossible for me to stay at home and fall asleep.

I'm sure there are smart mechanical engineers working on vibration free AC units, but until then I'm looking for a house.

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The propeller was invented 200 years ago. I think the aerodynamics for silent ones have been known for 70 years (laminar flow).

The rest is just politics - those who pay for the conditioning system are not the ones who suffer from the noise - and even if they were, they have no competence to differentiate.

Maybe if apartments had noise ratings, and they could charge neighboring buildings for the measurable loss of worth from noise. Maybe there are precedents from airfield politics.

Seconding mandatory noise ratings for buildings and all thermal conditioning machines. In Europe they've invented all sort of energy efficiency ratings to sell wares already, i don't see why it can't be be done for noise.

I believe what you describe is partly caused by a beat frequency: the humming of different units is at slightly different frequencies, giving a noise with time-varying perceived amplitude. This is much more disturbing than a constant noise.

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