For someone who knows enough to point out that dB is logarithmic, you seemed to have neglected the fact that sound is inverse-square for distance? Unless these neighbors are _literally_ located 100m outside the data center?
It's also not a uniform medium. Sound gets reflected by houses, the ground, resonance, so it can constructively interfere and have a extra few times the expected amplitude. This can make the sound quaver and become really annoying, too.
dB should generally be expressed at what distance it was measured, and you'll see this done all over the place.
In this case, you'd reach 70dB at about 1km from the 90dB at 100m source, assuming a spherical cow, but they could also be completely different datacenters.
OP was talking about datacenters in residential areas and quoted the 90db @ 100m value, which indeed is 70dB @ 1km distance, which is absolutely absurd and would make it impossible to live nearby. That's the original comment I've answered.
Then, OP edited the post and said it was 90dB @ 10m, which means 50dB @ 1000m, an okayish value (depending on the type and duration of the noise), but that's not a distance we were talking about before.
I know datacenters in my city that are less than 500m from residential zoning (I should note I'm not in the US and this is not a new datacenter), so I didn't think that the original (distance) measurement sounded absurd, that's why I pointed out how much the (noise) measurement seemed to be out-of-scale.
Anyways, I think OP's measures where just completely made up or misremembered, because I'm any way I've framed the data (and the edited data), it doesn't match my personal observations around the few datacenters I've been to nor the data that's been released.
I did agree about the possibility of low-frequency noises being a huge nuisance, though, as those types of noises feel much worse than random noises at random intervals at higher dB.